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UBC Theses and Dissertations

Analysis of mountain lion predation upon mule deer and elk in the Idaho Primitive area Hornocker, Maurice Gail 1967

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AN ANALYSIS OF MOUNTAIN LION PREDATION UPON MULE DEER AND ELK IN THE IDAHO PRIMITIVE AREA by MAURICE G. HORNOCKER B.Sc., University of Montana, 1960 M.Sc., University of Montana, 1962 A thesis submitted i n p a r t i a l f u l f i l l m e n t of the requirements for the degree of DOCTOR OF PHILOSOPHY in the Department of Zoology We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA November, 1967 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r an advanced degree at the U n i v e r s i t y o f B r i t i s h C o lumbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by the Head o f my Department o r by h i s r e p r e s e n -t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada Department nf ABSTRACT i This study was designed (1) to investigate the dynamics of a mountain lion population, and (2) to assess the impact of a population of lions on populations of big-game animals. The research was carried on in the Idaho Primitive area; intensive work was limited to the winter and early spring seasons. Lion population numbers were stable during the three-year study period, and available evidence indicates the present popu-lation level existed for some time prior to the start of the study-Intraspecific relationships, manifested through t e r r i t o r i a l i t y , acted to limit lion numbers and maintain population stability'.. Dispersal and mortality, particularly of young individuals, appeared to be important limiting mechanisms. The population was centered around a nucleus of mature individuals well-established on territories, but segments of the population were dynamic, exhibiting an inflow and outflow of individuals from season to season. These transients were composed predominantly of young animals. Strife appeared to be kept to a minimum by a "mutual avoidance" behavorial mechanism. Specific hunting territories were shared but appeared never to be used by more than one lion or family of lions at a time. Individuals, regardless of sex:,, appeared to respect the presence of another in a specific area. The "mutual avoidance" hypothesis is advanced as an important factor in the maintenance of lion populations. This mechanism provides for the i i d i s t r i b u t i o n of lions i n both space and time without costly-f i g h t i n g . It. also appears to insure greater success i n securing large prey animals. Population size of prey species -- mule deer, elk, and big-horn sheep -- was established by making ground and a e r i a l counts each year. Bighorn sheep numbers remained constant during the three-year period, but populations of deer and elk, the p r i n c i p a l prey species, increased. The range was considered overstocked by deer and elk. Forty-four elkqand 39 deer were recorded as d e f i n i t e l y k i l l e d by lions during the three-year period. Only two k i l l s of bighorn sheep were found; l i o n predation on this species appeared i n s i g -n i f i c a n t . Seventy-five percent of the elk k i l l e d by lions were 1% years old or less and 9% years or older; 57 percent of the deer k i l l s were i n these age classes. More "young" than "old" animals were k i l l e d . Lions were non-selective i n their k i l l i n g , except for "negative s e l e c t i v i t y " i n the case of mature b u l l elk. Factors acting separately or c o l l e c t i v e l y to increase prey v u l n e r a b i l i t y included prey density, behavior, age, health, in t e r - and perhaps i n t r a s p e c i f i c s t r i f e , and the lion's predatory c h a r a c t e r i s t i c s . It was concluded that elk and deer populations were limited by the winter food supply and that predation by lions was inconse-quential i n determining ultimate numbers of elk and deer. Lion predation, however, i s a powerful force acting to dampen and protract severe prey o s c i l l a t i o n s and to d i s t r i b u t e ungulates on r e s t r i c t e d , c r i t i c a l range. From the th e o r e t i c a l standpoint, i t also appears to be a strong evolutionary force, acting to remove less f i t individuals from the population. The effects and influence of such predation are considered of great significance i n the maintenance of ecologic s t a b i l i t y i n wilderness environments. TABLE OF CONTENTS PAGE ABSTRACT i TABLE OF CONTENTS i v LIST OF TABLES v i i LIST OF ILLUSTRATIONS ix ACKNOWLEDGEMENTS x INTRODUCTION 1 STUDY AREA . 3 Geographic Location and Physiography 3 Climate . . . . . 4 Vegetation . 5 Fauna. . . . . . . . . . 8 METHODS 11 General Methods 11 Capturing and Immobilizing 12 Marking „ . . . . 13 Weights and Measurements 14 Census . . . . . . . . . . . . . . . . . . . 15 Mountain Lion Population .15 Big-Game Populations . . . . 15 Age and Physical Condition of Big-Game Animals . . . . . . 16 Range Survey . = . . . . . . . . . 16 THE MOUNTAIN LION POPULATION . . . . 18 Numbers and Composition . . . . . . 18 V PAGE Petersen Index 20 Schnabel .Method . . . 22 Appraisal of Census Methods . 22 Resident Population 25 Possible Causes of Population S t a b i l i t y . „ 27 Mortality Factors . 28 Dispersal 30 Other Factors . 30 Home Ranges and T e r r i t o r i a l i t y 31 Individual Ranges . 32 Adult Males 32 Adult Females 34 Function of T e r r i t o r i a l i t y 40 PREY POPULATIONS. 46 Numbers . . . . . . . 46 Age and Sex Composition . „ . 52 Physical and N u t r i t i o n a l Condition ' . 53 MOUNTAIN LION KILLS . . . . . . . . 55 Physical Condition of K i l l s . . . . . . . . 59 FREQUENCY OF KILLING 63 PREDATION EFFICIENCY 70 THE MECHANICS AND FUNCTION OF MOUNTAIN LION PREDATION . . . . . 72 Density of Prey Populations 73 Density of the Mountain Lion Population Characteristics of the Prey Characteristics of the Predator The Function of Mountain Lion Predation: Conclusions . . . SUMMARY LITERATURE CITED . . . . . . APPENDIX BIOGRAPHICAL INFORMATION v i i LIST OF TABLES TABLE PAGE I . Results of administering Sernylan to mountain lions . . 13 I I . Mountain lions marked i n the Big Creek study area . . . 19 I I I . The mountain l i o n population ini the Big Creek study area, 1966-67 . 19 IV. Estimated mountain l i o n population i n the Big Creek area; recapture data adjusted for mortality 23 V . Composition of the Big Cr/eek mountain l i o n population, 1966-67 season 26 V I . Total cumulative numbers and c l a s s i f i c a t i o n of big-game prey animals observed. Big Creek -- Middle Fork drainage, 1964-67 47 V I I . Results of a e r i a l censes, Big Creek drainage, 1966 and 1967 . 48 V I I I . Actual counts and adjusted population estimates of elk and deer. Big Creek drainage, 1964-67 51 I X . Number of c a l f elk and fawn deer per 100 adult female elk and deer s Big Creek drainage, 1964-67 53 X . Elk and deer specimens collected at random, 1966-67 . . 54 X I . Age, sex, and physical condition of 44 elk k i l l e d by mountain l i o n s 9 1964-67 . 56 X I I . Age s sex, and physical condition of 39 deer k i l l e d by mountain l i o n s , 1964-67 . . . 57 X I I I . Composition of the Big Creek elk and deer populations and the percent represented by each class i n the t o t a l l i o n k i l l 59 X I V . Determination of physical condition of 33 elk and deer k i l l e d by mountain lions and 14 randomly collected elk and deer 9 1966-67 . . . 61 v i i i TABLE PAGE XV. Physical condition of 72 elk and deer k i l l e d by mountain li o n s , 1964-67 . . . . 62 . XVI. Live weights of elk and mule deer . 6 7 XVII. Physical condition of 72 mountain l i o n k i l l s : juvenile elk and deer compared to;adult elk and deer, 1964-67. . 78 XVIII. Relative proportion of juvenile elk and deer i n the population and the incidence of juveniles i n the recorded l i o n k i l l , 1964-67 80 ix LIST OF ILLUSTRATIONS FIGURE PAGE 1= Winter home range of three resident adult males . . . . 33 2. Winter home range of four resident adult females . . . 35 3. Home range of female Number 4 i n three winter seasons 37 4. Winter, home range of female Number 29 i n two winter seasons . . . . . . . . . 38 5. Winter home range of three resident adult males and four resident adult females . . . . . 39 X ACKNOWLEDGEMENTS This study was o r i g i n a l l y suggested by John R. Woodworths d i r e c t o r of the Idaho Fish and Game Department, and Dr. Paul D. D'.alke, Leader of the Idaho Cooperative W i l d l i f e Research Unit. They and Dr. I. McT. Cowan of the University of B r i t i s h Columbia were instrumental i n arranging a cooperative agreement for the conduct of the project. Major f i n a n c i a l support was provided by the Idaho Fish and Game Department and the University of B r i t i s h Columbia. Grants were .contributed each year by the Theodore Roosevelt Memorial Fund of the American Museum of Natural History, the Boone and Crockett Club, and the New York Zoological Society. The National W i l d l i f e Federation awarded a one-year fellowship to the i n v e s t i -gator i n 1965. Cooperation was generously provided by the U. S. Forest Service and the D i v i s i o n of Animal Services, U. S. Department of the Interior. A great many individuals contributed d i r e c t l y or i n d i r e c t l y to the undertaking. I am es p e c i a l l y indebted to Dr. I. McT. Cowan, chairman of my committee at the University of B r i t i s h Columbia, for his help throughout the study. He made many valuable suggestions concerning the conduct of the field" work and helped i n analyzing the data. Dr. Cowan's enthusiastic support and encouraging attitude was a tremendous help throughout the study. Dr. D. H. Chitty gave fr e e l y of his time and made many x i valuable comments for the preparation of this thesis. His help and encouragement throughout the study i s g r a t e f u l l y acknowledged„ The other members of my committee, Dr. H. D. Fisher, Dr. W. S. Hoar, and Dr. A. J. Wood assisted i n many ways and made he l p f u l suggestions i n the preparation of this manuscript. I extend my sincerest appreciation to a l l these persons. Personnel of the Idaho Fish and Game Department assisted i n many ways. Among those deserving special thanks are Charles Haynes, Levi Mohler, E r r o l Nielson, Wally Roberts, Dale Von Steen 5 Roger Williams, and John Woodworth. David Neider and Jerold Theissen allowed me to use unpublished data from their f i l e s . The confidence and support given me by the Idaho Fish and Game Commission i s also g r a t e f u l l y acknowledged. Mr. and_Mrs. Jess R. Taylor, owners of the Taylor Ranch, a deeded property i n the Primitive Area, made f a c i l i t i e s available at the ranch and helped i n many ways. I extend sincere thanks for their warm h o s p i t a l i t y and fine cooperation. Others who cooperated i n various ways were John Vines, Martin Rust, Wayne England, and Glenn Harper„ Mrs. " B i l l i e " O b e r b i l l i g , operator of the O b e r b i l l i g Mobile Telephone Service i n Boise, Idaho, provides radio services to the "back country"; her t i r e l e s s service deserves the highest praise. Veteran bush p i l o t s Bob Fogg, B i l l Dorris, and Gene Crosby of Johnson Flying Service i n McCall, Idaho, provided excellent service throughout the study. Others to whom I am indebted include E a r l Dodds. Sam D e f l e r } x i i and Jack Schmautz, a l l of the U. S. Forest Service; Homer Ford and Pat Reed, D i v i s i o n of Animal Services, U. S. Department of the Interior, and Kenneth A. Dick and J. S. Watts of the University of Idaho. Dr. H. E. Reinhardt assisted with s t a t i s t i c a l analyses and Charles Sperry did the scat analyses. For their personal inte r e s t I am gr a t e f u l to Dr. James A. Oliver, Director of the' American Museum of Natural History, to Dr. F a i r f i e l d Osborn, President of the New York Zoological Society, and to Richard Borden and John Rhea of the Boone and Crockett Club. Wilbur Wiles, a long-time resident of the Primitive Area.,, assisted i n a l l aspects of the study from the time of i t s inception--his help was the one most important factor i n actually carrying out the project. Mr. Wiles is a s k i l l e d woodsman and a keen observer, an u n t i r i n g , enthusiastic worker and a fine companion -- his p a r t i c i p a t i o n i n the study made i t much more rewarding. F i n a l l y , I must express my deepest gratitude to my family. My wife, Shirley, assumed f u l l r e s p o n s i b i l i t y for the family during my absence through many lonely winter months and retained her cheerful attitude throughout. My daughters Karen, Kimberly, and Lisa accepted my absence gracefully each year. The patience and understanding of my family made a d i f f i c u l t task much easier. INTRODUCTION 1 Rel a t i v e l y l i t t l e i s known of the population dynamics and ecology of the mountain l i o n (Felis Concolor). Hibben (1937, 1939) accompanied hunters i n the south-western United States and attempted to determine the extent of l i o n predation. Young and Goldman (1946) compiled information obtained largely from hunters engaged i n control programs. Robinette et al_. (1959, 1961) collected hunter-k i l l e d specimens i n Utah and Nevada and reported on food habits and productivity. The bulk of the l i t e r a t u r e , however, deals with ranges, sightings, and s p e c i f i c instances of a "nature note" variety. The need for detailed b i o l o g i c a l and ecological information on this species i s obvious. Cahalane (1964) surveyed the status of the mountain l i o n and found that nowhere i n the United States, with the possible exception of Fl o r i d a , were numbers increasing. He concluded that i t s future seems to depend on the retention of s u f f i c i e n t wilderness habitat. Hunting pressure by stockmen and sport hunters, largely unregulated i n the western United States, i s increasing as the human population expands. Objective data are needed not only to preserve the l i o n and manage i t i n t e l l i -gently but to better promote an understanding of i t s role i n the ecological scheme. This investigation had two major aims: (1) to study a l i o n population, and (2) to assess the impact of this population on i t s prey, p a r t i c u l a r l y the big-game animals. In view of the obvious d i f f i c u l t y of such an endeavor, c a r e f u l consideration was given 2 to the study area. I t r i e d to find an area where both lions and ungulates were f a i r l y abundant, where there was l i t t l e livestock, and not too much hunting. Such an area was found i n the Idaho Primitive Area. To simplify study parameters futther, intensive study was limited to winter and early spring when snow confines both lions and the i r prey to a r e l a t i v e l y small sector of the t o t a l range. STUDY AREA 3 Geographic Location and Physiography The Idaho Primitive Area i s i n Central Idaho contiguous to and south of the Salmon River.." 'Roadless and e x i s t i n g i n e s s e n t i a l l y a wilderness state, i t extends roughly 60 miles north - south and 40 miles east - west encompassing approximately 2,000 square miles (Douglas, 1964). The Primitive Area covers portions of four National Forests - the Payette, Salmon, Boise, and C h a l l i s ; unpopulated expanses of wilderness s t i l l e x i s t beyond i t s boundaries i n many places. The topography i s characterized by high mountain peaks and ridges, dissected by numerous deep, narrow v a l l e y s . This area has the greatest r e l i e f of any part of Idaho (Daubenmire, 1952). The Chamberlain Basin area, a "plateau" lying between 5,000 and 6,000 feet i n elevation i n the northern portion of the Primitive Area i s an exception. It i s characterized by more gently r o l l i n g h i l l s , numerous mountain meadows, and broader stream courses. The primary watershed i n the Primitive Area i s the Middle Fork of the Salmon River for the lower 75 miles of i t s course. The Salmon River canyon and the Middle Fork and South Fork t r i b u t a r i e s cut deep, into the huge Idaho batholith, a vast g r a n i t i c mass measuring some 70 by 240 miles (Smith, 1954). This body of granite, formed during the Cretaceous i s one of the largest of i t s kind i n the world (Shenon and Reed, 1936). The Salmon canyon i s recognized as one of the most rugged i n North America; i n several places i t s depth exceeds 6,000 feet. Large areas along the canyon are bordered by c l i f f s and the talus originating from them. The high country i s characterized by subalpine valleys surrounded by ridges studded with spires of jagged rock. Glaciated basins are rimmed with talus and outcroppings of barren granite (Smith, 1954). The canyons of the Salmon and i t s major t r i b u t a r i e s are the most s t r i k i n g physiographic feature of the region. In an ecologic sense, they are unique to the intermountain area. This inve s t i g a t i o n was carried on primarily i n the Big Creek drainage, a major tributary of the Middle Fork. This stream, over i t s lower 28 miles, f a l l s from 5,000 feet elevation to 3,400 feet, an average gradient of 57 feet per mile. Mountain peaks within the Big Creek drainage r i s e to more than 9,400 feet. Climate The Salmon River drainage has a rather hot dry climate. At the Salmon weather station, approximately 50 miles east of the study area, (elevation 3,961 f e e t ) , the mean annual p r e c i p i t a t i o n over a 55-year period was less than nine inches (U. S. Department of Commerce, 1966). Weather records available from mountainous Big Creek, about 20 miles west of the study area, (elevation 5,686 fe e t ) , indicate average p r e c i p i t a t i o n to be about 30 inches annually. Annual p r e c i p i t a t i o n on the study area i t s e l f l i e s somewhere between these extremes, but i s more properly represented by the Salmon data. Most of this p r e c i p i t a t i o n i s received from late f a l l to early spring. Six to eighteen inches of snow can be expected on most of the study 5 area winter ranges from late December through February, and often well into March. Southern exposures often are bare, however, while 18 to 24 inches of snow i s found on north-facing slopes. Snow accumulates with an increase i n elevation and often exceeds 10 feet on the higher ridges. Temperatures of more than 100 F. are often recorded during July and August. Sub-zero temperatures can be expected for short periods from December through mid-March. The lowest recorded reading for the study period was -33 F. at Monumental Creek on December 17, 1964. Vegetation Daubenmire (1952) recognizes ten vegetation zones i n Idaho. These zones are distinguished by the nature of the climatic climax associations occurring at d i f f e r e n t elevations or i n d i f f e r e n t regions. Four of these zones, the Ponderosa pine zone, the Douglas f i r zone, the spruce-fir zone, and the alpine zone occur i n the Idaho Primitive Area. The vegetation i s variable because of extreme differences i n elevation and topographic r e l i e f , variations i n s o i l and exposure, and disturbances r e s u l t i n g from f i r e s , grazing, and insect outbreaks. Zonation, i n the ..sense of belts which can be r i g i d l y defined i n terms of elevation above sea l e v e l or of c e r t a i n species only, i s d i f f i c u l t to detect i n some areas and impossible i n others. Ponderosa pine (Pinus ponderosa) constitutes p r i n c i p a l zone along the lower r i v e r breaks (Douglas, 1964). In some places there are 6 downward extensions of the ponderosa zone to elevations bordering the r i v e r . In other areas, grassy slopes reach to the r i v e r . Open grassland parks interspersed with stands of ponderosa pine occur i n many situations. The p r i n c i p a l species of grass i s Agropyon spicatum. Festuca idahoensis, Poa secunda, and Calamagrostis rubescens are other important species. Cheatgrass (Bromus tectorum) occurs i n a few overgrazed areas. Important shrubs i n this zone are mountain mahogany (Cercocarpus l e d i f o l i u s ) , bitterbrush (Purshia tridentata), big sagebrush (Artemisia tridentata), spring greasbush ( F o r s e l l e s i a  spinescens), and rubber rabbitbrush (Chrysothamnus nauseosus). There are many forbs, of which balsamroot (Balsamorhiza sagittata) is the most common. The ponderosa pine zone cons titutesy. the winter range for big game populations along Big Creek and the Middle Fork. Overgrazing on the Middle Fork i s slowly changing the predominantly browse-type range to grass type (Douglas, 1964). This problem has not yet arisen on Big Creek although game pressure on available browse has been heavy for a number of years. The Douglas f i r zone occurs above the ponderosa pine zone and occupies the greatest a l t i t u d i n a l range i n the Idaho Primitive Area. This zone extends down the canyon slopes to the r i v e r on some of the northern exposures and good stands of Douglas f i r (Pseudotsuga menziesii) occur to well over 7,000 feet on the ridges. In the Chamberlain Basin and similar- areas, this species has been largely 7 replaced by lodgepole pine (Pinus contorta). This undoubtedly i s the r e s u l t of f i r e s and McDougall and Baggley (1956) believe that two to three f i r e s each century are s u f f i c i e n t to perpetuate these stands. Ninebark (Physocarpus malvaceus) i s the most common shrub i n this zone. Aspen (Populus tremuloides) occurs i n more mesic s i t e s . A big sagebrush (Artemisia tridentata)-grass community occurs i n areas throughout the ponderosa pine and Douglas f i r zones, p a r t i c u l a r l y on south-and west-facing slopes and i n "mountain parks". Daubenmire (1943) states that this plant cover i s si m i l a r to that of the basal plains, and i n the c e n t r a l Rockies sagebrush is dominant on the west slope. Engelmann spruce (Picea engelmannii) and alpine f i r (Abies  lasiocarpa) characterize the spruce-fir zone, which l i e s above the Douglas f i r zone. It abutts a true alpine zone on some of the highest peaks. The Bighorn Crags provide the most outstanding example of this habitat i n the Primitive Area. Stunted and deformed white-bark pine (Pinus a l b i c a u l i s ) occurs on the higher slopes. Beargrass (Xerophyllum tenax), rhododendron (Rhododendron albiflorum), and dwarf huckleberry (Vaccinium scoparium) are c h a r a c t e r i s t i c understory species. The alpine zone occurs only on the highest peaks and ridges. Vegetation consists of only a few crevice and mat plants, such as Phleum alpinum, Salix r e t i c u l a t a , Erigeron compositus, and Saxifraga spp. (Daubenmire, 1952). 8 Fauna The faunal association within whic h\ ^ hii-mouiit'ain: libn'o£ this study were l i v i n g i s important to an understanding of prey selection. Several species of large herbivores inhabit the Primitive Area. These include elk (Cervus canadensis), mule deer (Odocoileus  hemionus), bighorn sheep (Ovis canadensis) and mountain goats (Oreamnos americana). White-tail deer (Odocoileus virginianus) and moose (Alces alces) occur i n lesser numbers i n c e r t a i n areas. Mule deer are the most abundant big game species, but elk have been increasing rapidly over much of the area i n recent years (Douglas, 1964). Larger carnivores inhabiting the Primitive Area are mountain lions ( F e l i s coneolor), black bear (Ursus americanus), and coyotes (Canis latrans). Bobcats (Lynx rufus) are common and lynx (Lynx  canadensis) and red fox (Vulpes fulva) are present i n lesser numbers. Wolverines (Fulo luscus) are reported occasionally and badgers (Taxidea taxus) are f a i r l y common. Furbearing species include r i v e r otter (Lutra canadensis), beaver (Castor canadensis), marten (Martes  americana), mink (Muste11a vison), and muskrat (Ondatra zibethicus). Skunks (Mephitis mephitis), spotted skunks (Spilogale putorius), long-tailed weasel (Mustela frenata) and shor t - t a i l e d weasel (Mustela erminea) occur* over much of the area. Fisher (Martes  pennanti) have recently been released i n the area (Douglas, 1964). . -Manyldifferent-Species^ofurodents and lagomorphs occur throughout the Primitive Area. A great number of bird species 9 u t i l i z e the diverse habitat. Some of these are year-round residents, but the majority nest here i n summer and migrate each f a l l . Environmental conditions for the large mammals have changed since the late 1800's. Bighorn sheep were quite abundant at this time -- early s e t t l e r s reported seeing sheep "by the thousands" (Smith, 1954). Mule deer numbers were apparently below those of more recent times. Available information indicates that elk were confined to small l o c a l populations i n the Chamberlain Basin area. A major decline occurred i n bighorn sheep populations around 1880, and these populations have never returned to primitive levels (Smith, 1954). In more recent years, mule deer populations b u i l t up to extremely high levels i n Big Creek and the Middle Fork drainages -- conservative estimates ranged from 12,000 to 15,000 i n the Middle Fork area alone (Kindel, 1960). These populations crashed i n the late 1940's. The best available information indicates that these populations have returned to more moderate lev e l s , and i n some areas of the Middle Fork appear to have s t a b i l i z e d (Wood, 1962). No data, however, are available for the past f i v e years. Elk numbers in Big Creek and portions of the Middle Fork have b u i l t up steadily over the past several years. Smith (1954) notes that elk were seen occasionally i n the Middle Fork i n summer, but none wintered there u n t i l the late 1930's. He further states that by 1954 they were abundant i n Cabin and Cow creeks i n the Big Creek drainage. They now are numerous throughout the Big Creek and Middle Fork drainages 10 and wintering populations are increasing. Mountain lions were subjected to moderately heavy bounty hunting -- from 10 to 15 lions were k i l l e d each year -- u n t i l the late 1950's when bounty payments were halted. S ince that time the population has received l i g h t hunting pressure i f any at a l l . METHODS 11 General Methods The study was carried on i n an area approximately 200 square miles i n size i n the Big Creek and Middle Fork drainages. Eight camps were established at six -- to ten -- mile intervals at various elevations; each was completely stocked with provisions and equipment p r i o r to the s t a r t of f i e l d work. Headquarters were maintained at the Taylor Ranch, on lower Big Creek. Access i n winter was limited to l i g h t , ski-equipped a i r c r a f t ; t r a v e l on the study area i t s e l f was by foot only. Communication to "outside" communities was by short-wave radio. Mr. Wilbur Wiles, an experienced l i o n hunter and long-time resident of the Primitive Area, assisted i n a l l aspects of the study. Capturing, i n d i v i d u a l l y marking, and subsequently recaptur-ing lions was the basic method of obtaining data. The study area was hunted as' systematically as possible. Normally Mr. Wiles and I spent two to f i v e days hunting each area before moving to the next camp. Weather and other conditions determined where we searched. Evaluating predation and i t s e f f e c t on big game prey populations coincided with other f i e l d a c t i v i t i e s . Two to f i v e weeks were spent each summer and f a l l on the study area i n an attempt to learn of l i o n movement and a c t i v i t y . Intensive work began each year i n late November and continued u n t i l late A p r i l or early May. A three-year t o t a l of 430 days was spent i n actually searching for and tracking mountain l i o n s ; an additional four to six weeks were 12 required each year to prepare and stock camps i n the f a l l and to dismantle camps i n the spring. Approximately 3,724 actual hunting and tracking miles were traveled on foot during the study. This figure represents a minimum number -- miles traveled each day were computed from U. S. Geological Survey 7% minute quadrange maps and represent only a i r - l i n e distances. Capturing and Immobilizing Trained dogs were used to capture the li o n s . Lions normally climbed trees to escape the dogs but on some occasions they sought refuge i n steep b l u f f s or i n caves. An average of 4.26 days of actual hunting and tracking was required for each capture and recapture. Thirty-nine lions were captured and marked during the three-years. Twenty-six individuals were recaptured 62 times. Thus 101 captures were made during the study. A l l lions handled were given intramuscular injections of "Sernylan", a brand of phencyclidine hydrochloride developed by Parke, Davis and Company. Dosages were computed from an estimate of each lion's weight and i t s apparent physical condition. The drug was administered by automatic propulsion syringes (Hornocker, et a l . , 1965) f i r e d from a s p e c i a l l y designed powder-charge gun. Sernylan, when injected i n cats acts primarily on the central nervous system by depression (Chen, et al., 1959). Dosages adminis-tered i n this study calmed but did not immobilize the animals (although complete immobilization may be achieved by increasing the 13 dosage). Lions immobilized by drugs such as succinylcholine chloride, may f a l l from trees and injure or k i l l themselves (Hornocker, e_t al_. , 1965) ; phencyclidine hydrochloride presented no such problems. Drugged lions usually remained i n the tree and could be lowered by rope to the ground. Some lions jumped from the tree upon being injected. Those not immediately re-treed by the dogs were e a s i l y approached on the ground, usually within one-half mile. Table I summarizes the results of administering Sernylan to 57 lions over a three-year period. Table I Results of Administering Sernylan to Mountain Lions Summary 1964-67 Average Number Average Dosage, Minutes U n t i l No. Dosages mg. per Lb. Average Latent Completely Administered Body Wt. Period (Minutes) Manageable 57 1:1.95 6 12 Marking A l l lions except Numbers 30 and 31, which were young kittens, were marked i n both ears with numbered aluminum c a t t l e tags, i n d i v i d -u a l l y colored. Tags were placed i n the upper or leading edge of the ear close to the head. Different colored p o l y v i n y l chloride streamers, about two inches long, were threaded through a s l i t i n the lower edge of each 14 ear (Craighead and Stockstad, 1960). These were used as an additional i d e n t i f y i n g aid i n the event the animal was sighted or k i l l e d by someone not involved i n the project. D i f f e r e n t types of braided polyethylene rope c o l l a r s were placed around the necks of some adults. A l l c o l l a r s were f i t t e d rather loosely and none was capable of with-standing more than 70 pounds p u l l before breaking, should the c o l l a r s become entangled. A l l lions were tattooed i n one or both ears; Numbers 8 and 10 were exceptions. This marker i s permanent and i f properly applied w i l l i d e n t i f y the animal throughout i t s l i f e . Some lions recaptured i n 1967 had l o s t a l l t h e i r markers and were i d e n t i f i a b l e only by the tattoo, pointing up the value of d i f f e r e n t types of markers. Weights and Measurements Lions were suspended i n a nylon net and weighed on a portable spring scale. Three spring scales were used i n conjunction for the heavier cats; each had a capacity of 80 pounds and was graduated i n one. pound increments. I tested two and three scales i n conjunction and found them to be highly accurate. Weights for Numbers 8, 10, 20, and 28 were estimated, a l l other lions were weighed. Body measurements were made with a ten-foot s t e e l tape. Measurements were as follows: Total length -- nose to end of terminal vertebrae; t a i l length -- base of t a i l to end of terminal vertebrae; neck circumference -- around neck i n region of o c c i p i t a l condyle; body circumference -- around body immediately behind forelegs; height at shoulder -- top of scapula t O i h e e l of foot 15 pad, foreleg extended. Measurements of the feet and canines were made with a vernier c a l i p e r . Census Mountain Lion Population. Censuses of the l i o n population were made i n two ways: (1) capturing and i n d i v i d u a l l y marking, and (2) by combining capture-recapture information with track data. Capture data were treated cumulatively for the three year period, consideration being given to known mortality and suspected d i s -persal. Tracks enabled me to i d e n t i f y family groups but not a l l lone individuals or pairs. The time and date c e r t a i n tracks were made (judged by snowfall and snow conditions) i n r e l a t i o n to the time when individuals were captured i n a ce r t a i n area gave an insight into l i o n numbers. Big-Game Populations. Big game populations were counted on the ground and from the a i r . Ground counts were made throughout each of the three f i e l d seasons. The sex and age composition (age: adult, juvenile) of a l l game herds was recorded when possible. A 7 x 35 binocular was used i n making the counts. A e r i a l counts were made i n mid-April i n 1966 and 1967. The f l i g h t s were made i n early morning i n a fixed-wing Cessna 182 p i l o t e d i n both years by William Dorris. Weather and range conditions were similar i n both years and the same routes were followed. Supplementing the a e r i a l count information are data obtained 16 by a helicopter census. Personnel of the Idaho Fish and Game Department conducted this census of the Big Creek drainage A p r i l 23-26, 1967, one week la t e r than my a e r i a l counts. Range conditions remained unchanged for the two counts. Age and Physical Condition of Big Game Animals Physical condition of elk and deer k i l l e d by lions and those coll e c t e d i n an attempt to sample the n u t r i t i o n a l state of the population was determined by examining the whole carcass (when possible) and by examining bone marrow from the femur. Technique and procedure described by Cheatum (1949) and Rausch (1950) were followed i n 1964-65 and 1965-66, except that no microscopic examinations were made. Color and consistency of the marrow were the major c r i t e r i a u t i l i z e d i n the determinations. In 1966-67 I also used a procedure outlined by B.ischoff (1954). "Good", " f a i r " , and "poor" classes were established and animals assigned to a p a r t i c u l a r class on the basis of the femur marrow color and consistency. Marrow samples were taken from each k i l l , preserved i n formalin, and analyzed for fat content. Ether extraction was the technique used i n the laboratory fat analyses. Age of deer and elk was arrived at by comparing wear of the cheek-teeth with that of known-age specimens. C r i t e r i a used to d i s t i n g u i s h age classes by Robinette e_t aj.. (1957) for mule deer and by Quimby and Gaab (1957) for elk were also followed. Range Survey Six areas considered to be key winter range areas for big 17 game were sampled i n the spring of 1967. This was done to determine condition and u t i l i z a t i o n of key forage species on these heavily used areas. Cole (1958) defines a key forage species as one of the most important p,ig game foods on a range. He further defines a key range area as those portions of the winter range which receive the heaviest use. These c r i t e r i a were considered i n the sampling undertaken i n this study. The "Wandering Quarter" (Dix, 1961) technique was u t i l i z e d i n selecting sample plants, and the "Cole Method" (Cole, 1958) was used to determine plant condition and u t i l i z a t i o n . One hundred browse plants were sampled i n each of the six key areas. Data were recorded on standard U. S. Forest Service form sheets. 18 THE MOUNTAIN LION POPULATION Numbers and Composition Population studies were confined to the Big Creek Drainage. Only limited work was carried on i n the Chamberlain - Disappointment area 'gnd no attempt was made to determine population size. Thirty-two of the 39 individuals marked during the three-year period were captured i n the Big Creek study area: 10 i n 1964-65, 14 i n 1965-66, and 8 i n 1966-67. ' The 32 animals included 12 adult males, 9 adult females, and 11 juveniles. These figures are cumulative and the number of juveniles, with respect to population size for a given year, i s misleading. "Juveniles" are considered those individuals s t i l l with their mother and apparently dependent upon her. Some "juveniles" marked i n 1964-65 and 1965-66 should be considered "adults" i n 1966-67. These include f i v e females and two males. If these are advanced to the adult c l a s s , assuming no mortality and no dis p e r s a l took place, then the present makeup of a l l lions marked i n Big Creek becomes 14 adult males, 14 adult females, and 4 juveniles. (Table II). To arrive at the actual population size for a given year, however, adjustments must be made to the above figures. Six known mort a l i t i e s were recorded, four marked lions and two unmarked. Additional mortality, p a r t i c u l a r l y of the young, and dispersal are suspected. Table III presents the known and suspected population of lions i n the Big Creek area for the winter of 1966-67 and how the determinations were made. Fi f t e e n individuals were Table II Mountain Lions Marked i n the Big Creek Study Area 1964 - 67 Adult Males Adult Females Juveniles* Lion number: M F 2 1 3 4 13 6 5 11 19 14 7 12 27 15 8 16 30 17 9 21 23 10 24 25 18 29 31 20 32 22 26 28 '''Juveniles at time of i n i t i a l capture Table III The Mountain Lion Population i n the Big Creek Study Area 1966 - 67 How Determined Captures Tracks Adult Males 4 2 Adult Females 7 1 Juveniles 4 1 Captures i n Suc-cessive Years TOTAL _2_ 8 10 GRAND TOTAL - 23 20 captured one or more times. A female with a single k i t t e n was tracked on two occasions, and d i s t i n c t i v e tracks of two males were observed several times. One of these males i s believed to have been Number 10, an extremely large old male, the other i s believed to have been unmarked. Included i n Table III are four lions (Numbers 6, 7, 17 and 19) captured i n previous years -- 1964-65 and 1965-66 -- and therefore considered residents of the area even though they were not captured i n 1966-67. Data i n Table III suggest that 23 lions were present on the study area i n the winter of 1966-67. I believe this figure repre-sents a minimum population number. Further, this census, arrived at i n the same manner, has been remarkably similar i n each of the three years -- after the f i r s t f i e l d season i n 1964-65 I estimated a minimum of 22 lions i n the Big Creek area. The known minimum number at the end of the 1965-66 season was 24. These data suggest a stable population of mountain lions i n the Big Creek area. Peterson Index. The Peterson Index, a method of computing t o t a l population from ratios.: of recaptured marked animals to i n i t i a l l y captured unmarked animals (Peterson, 1896), was applied to the capture - recapture data. The formula used i n this method is : 21 where: P = t o t a l population estimate M = number of animals marked and released, f i r s t trapping e f f o r t S = t o t a l number of animals captured, second trapping e f f o r t R = number of animals recaptured, second trapping e f f o r t Because "trapping" was carried on continuously during each of the three f i e l d seasons, modifications must be made for " f i r s t and second" trapping e f f o r t s . Davis (1960) states that i d e a l l y the marking and releasing should be a l l done at one time (a day) and the recaptures also at one time (another day). He further states "However, i n many cases, so few animals are caught i n one day that the method i s inapplicable. In these cases i t i s permissable to group together the captures for a period (a week perhaps) and assume that a l l were made on the same day." Obviously the technique cannot be applied to captures made of mountain lions i n one week or even one season. Therefore, I have treated the three-year. capture - recapture data i n composite form. Thirty-two lions were marked i n the Big Creek area during thr three-year period. Ten lions were captured the f i r s t year; therefore 10 is considered the " f i r s t trapping e f f o r t " (M). Twenty-one individuals were recaptured during the three-year-study; therefore S becomes 53, the t o t a l number of lions captured i n the "second trapping e f f o r t " (32 + 21). R equals 21, the 22 number o f a n i m a l s r e c a p t u r e d . When the P e t e r s e n Index f o r m u l a i s a p p l i e d to t h e s e f i g u r e s , a p o p u l a t i o n f i g u r e o f 25 i s computed. T h i s i s o n l y s l i g h t l y h i g h e r t h a n 23, the f i g u r e o b t a i n e d by c o m b i n i n g c a p t u r e and t r a c k d a t a . S c h n a b e l Method. The S c h n a b e l Method ( S c h n a b e l , 1938), m o d i f i e d by L o r d (1957) f o r e s t i m a t i n g fox p o p u l a t i o n s u s i n g r e c a p t u r e d a t a and a d j u s t i n g f o r m o r t a l i t y d u r i n g the t r a p p i n g p e r i o d , was a p p l i e d t o the B i g C r e e k d a t a ( T a b l e I V ) . The u n a d j u s t e d c o m p u t a t i o n s r e s u l t i n a p o p u l a t i o n e s t i m a t e o f 3 0 , s i m i l a r to the f i g u r e o b t a i n e d by use o f the P e t e r s e n Index. When adjustments a r e made f o r known m o r t a l i t y , the e s t i m a t e becomes 25, q u i t e s i m i l a r to the e s t i m a t e based on more d i r e c t methods. A p p r a i s a l o f Census Methods From the c a p t u r e - t r a c k d a t a , i t i s known w i t h c e r t a i n t y t h a t n i n e t e e n o f the e s t i m a t e d 23 i n d i v i d u a l s were p r e s e n t on the s t u d y a r e a i n 1966-67. F i f t e e n o f t h e s e were c a p t u r e d , the o t h e r f o u r , two l a r g e males and a female w i t h a s i n g l e k i t t e n , l e f t d i s t i n c t i v e t r a c k s . The o t h e r f o u r l i o n s , a mature m a l e , a young a d u l t m a l e , and two young a d u l t f e m a l e s , were c a p t u r e d a t o t a l o f 10 t imes i n s u c c e s s i v e y e a r s (1964-65 1 9 6 5 - 6 6 ) . They t h e r e f o r e a r e c o n s i d e r e d r e s i d e n t s o f the a r e a , b u t the p o s s i b i l i t y e x i s t s t h e y were n o t p r e s e n t i n 1966-67. S n o w f a l l i n 1966-67 was l i g h t i n the a r e a s i n h a b i t e d by t h e s e l i o n s making h u n t i n g c o n d i t i o n s d i f f i c u l t . I b e l i e v e t h e s e l i o n s and perhaps 23 Table IV Estimated Mountain Lion Population i n the Big Creek Area; Recapture Data Adjusted for Mortality (after Lord, 1957) Time Period No. No. Marked Marked Marked Recaptured Unadjusted Adjusted A C B D AB AD Dec 1, 1964 • May 1, 1965 10 0 0 0 0 0 Nov 24, 1965 May 1, 1966 14 10 8 140 112 Nov 30, 1966 May 1, 1967 8 7 11 24 20 192 160 332 272 (A B) 332 P = Q = - j y = 30 l i o n s , unadjusted (AD) 272 P = Q = "YJ~ = 25 l i o n s , adjusted for mortality 24 o t h e r s were t r a c k e d i n 1966-67 b u t , as s t a t e d , t h e s e d a t a a r e u n r e l i a b l e and a r e n o t c o n s i d e r e d . The P e t e r s e n Index, as w e l l as the o t h e r method, makes some b a s i c a s s u m p t i o n s : (1) no l o s s o r g a i n o f m a r k e r s ; (2) no r e c r u i t m e n t ; (3) no d i f f e r e n c e i n m o r t a l i t y o f marked and unmarked i n d i v i d u a l s ; (4) c a t c h a b i l i t y i s the same i n marked and unmarked i n d i v i d u a l s ( D a v i s , 1960). A s s u m p t i o n s 1, 3 , and 4 may be a c c e p t e d as t r u e i n t h i s t r e a t m e n t . A s s u m p t i o n 2 does become a f a c t o r when the d a t a f o r a t h r e e - y e a r p e r i o d a r e grouped t o g e t h e r . The B i g C r e e k p o p u l a t i o n , however, i s b e l i e v e d to be s t a b l e . In t h i s s i t u a t i o n b i r t h s and i m m i g r a t i o n a r e o f f s e t by m o r t a l i t y and perhaps d i s p e r s a l . The p o p u l a t i o n e s t i m a t e o f 25 a r r i v e d a t by t h i s method appears r e a l -i s t i c . When L o r d ' s (1957) m o d i f i c a t i o n were a p p l i e d to the S c h n a b e l Method, the r e s u l t s o b t a i n e d were q u i t e s i m i l a r to those o f the d i r e c t method o f c a p t u r e - t r a c k d a t a . The u n a d j u s t e d ( f o r m o r t a l i t y ) c a l c u l a t i o n s c o r r e s p o n d c l o s e l y w i t h the c u m u l a t i v e number o f i n i t i a l c a p t u r e s - - 30 v s . 32. A d j u s t e d f o r known m o r t a l i t y , t h i s method r e s u l t s i n a p o p u l a t i o n e s t i m a t e o f 25, q u i t e c l o s e to 23, the number o f l i o n s i n d i c a t e d by my f i e l d d a t a . To sum u p , I b e l i e v e the f i g u r e s o b t a i n e d t h r o u g h c a p t u r e -r e c a p t u r e i n f o r m a t i o n and t r a c k d a t a , and a p p a r e n t l y s u b s t a n t i a t e d by the above p o p u l a t i o n e s t i m a t i o n methods, a r e a r e a s o n a b l y a c c u r a t e d e t e r m i n a t i o n o f minimum p o p u l a t i o n numbers i n the B i g C r e e k a r e a . 25 Resident Population Recapture data revealed that a segment of the population was made up of. transients, In order to delineate the population better, three categories were set up as follows (after Hawley and Newby, 1957): (1) Transients -- lions captured only once. (2) Temporary residents -- lions captured more than once i n a single season only. (3) Residents -- lions captured i n successive seasons, and juveniles s t i l l with their mother. Eleven of the 32 lions captured during the study were transients, three were temporary residents, and 18 were residents. A l l of the transients were adults or young adults, but eleven of those considered residents and temporary residents were juveniles at the time of i n i t i a l capture. One of these juveniles was k i l l e d . Six juveniles, s e l f s u f f i c i e n t i n 1966-67 may have l e f t the area. The remaining four were young kittens i n 1966-67, s t i l l with their resident mothers. Therefore, the actual known resident population i n 1966-67 consists of four adult males, four adult females, and four juveniles. The breakdown of the 23 lions known to be i n the Big Creek area i n 1966-67 i s presented i n Table V. A l l individuals l i s t e d as residents i n Table V, with the exception of Number 29, meet the c r i t e r i a set forth above. Number 29 was f i r s t captured i n 1966-67, but her d i s t i n c t i v e tracks revealed she had been on the area since the s t a r t of the study. Transients i n Table V were lions captured for the f i r s t time i n 1966-67; none of these was 26 recaptured. Those marked lions l i s t e d as undetermined -- Numbers 6, 14, 15, 17, and 19 -- were juveniles when f i r s t captured and subsequently recaptured. Numbers 6, 17 and 19 were not captured i n 1966-67 and i t i s not known with certainty i f they established residence on the area. Numbers 14 and 15 were captured the past season, but Number 15 was l a t e r k i l l e d 60 miles distant. It i s possible Number 14 also l e f t the area. The status of the unmarked lions designated i n Table V by "X" i s not known. They may be residents despite the fact we have not captured them. Table V Composition of the Big Creek Mountain Lion Population, 1966-67 Season Residents Adult Males Adult Females Juveniles 4 TOTAL 12 Lion No. 3, 7, 10, 18 4, 11, 12, 29 25, 27 30, 31 Transients Lion No. 26, 28 Undetermined Lion No. 32 _1_ 8 19, X* 6, 14, X* 15, 17 .X* * Unmarked individuals The number of lions c l a s s i f i e d as transients indicates that many animals were only passing through the area. The fact that these lions did not es t a b l i s h residence supports the view that the Big Creek population i s stable. Data on mortality and dispersal of 27 younger i n d i v i d u a l s f u r t h e r s u p p o r t t h i s c o n t e n t i o n . C a n n i b a l i s m by an a d u l t male was documented i n the w i n t e r o f 1965-66 and t h r e e young marked l i o n s were s h o t f a r from where t h e y were marked. Summing u p , the B i g C r e e k p o p u l a t i o n i s r e l a t i v e l y s t a b l e b u t segments o f the p o p u l a t i o n a r e d y n a m i c , e x h i b i t i n g an i n f l o w and o u t f l o w o f i n d i v i d u a l s from s e a s o n to s e a s o n . T h e r e i s a n u c l e u s o f m a t u r e , w e l l - e s t a b l i s h e d i n d i v i d u a l s b u t t h e r e i s a l s o a more f l u i d segment o f the p o p u l a t i o n composed p r e d o m i n a t e l y o f younger a n i m a l s . P o s s i b l e Causes o f P o p u l a t i o n S t a b i l i t y I t i s g e n e r a l l y r e c o g n i z e d t h a t m o u n t a i n l i o n s may have young a t any t ime o f the y e a r and t h a t l i t t e r s number m o s t l y from two t o f o u r . R o b i n e t t e e t a l . (1961) found an average o f 2.9 f o r 258 p o s t n a t a l : l i t t e r s w i t h a range o f one to f i v e ; f o r 66 p r e n a t a l l i t t e r s the average was 3 . 4 w i t h a range o f one t o s i x . Young and Goldman (1946) s t a t e t h a t l i t t e r s i z e ranges from one to s i x b u t i n U t a h the number i s u s u a l l y one t o t h r e e . In . t h i s s t u d y t h e r e were two l i t t e r s o f two and f o u r l i t t e r s o f t h r e e . A l l young were b e l i e v e d b o r n i n s p r i n g o r e a r l y summer. Because l i o n s a r e c a p a b l e o f b r e e d i n g a t any t ime o f the y e a r and p r o d u c i n g r e l a t i v e l y l a r g e l i t t e r s , i t m i g h t be assumed t h a t l i o n s a r e p r o l i f i c and t h a t l i o n p o p u l a t i o n s have a h i g h r a t e o f t u r n o v e r . No d a t a a r e a v a i l a b l e i n the l i t e r a t u r e , b u t f i n d i n g s made i n t h i s s t u d y do n o t agree w i t h t h i s s u p p o s i t i o n . I t has been shown t h a t p o p u l a t i o n numbers remained s t a b l e f o r the t h r e e - y e a r s t u d y p e r i o d . The b e s t a v a i l a b l e i n f o r m a t i o n 28 i n d i c a t e s the p r e s e n t p o p u l a t i o n l e v e l e x i s t e d f o r some time p r i o r t o the s t a r t o f the s t u d y . I b e l i e v e m o r t a l i t y and d i s p e r s a l a r e i m p o r t a n t i n m a i n t a i n i n g t h i s p o p u l a t i o n s t a b i l i t y and i n b o t h c a s e s young l i o n s a r e most a f f e c t e d . M o r t a l i t y F a c t o r s . The rugged t e r r a i n , p l u s the f a c t t h a t c a r c a s s remains a r e q u i c k l y consumed o r c a r r i e d o f f by s c a v e n g e r s , make m o r t a l i t y d a t a d i f f i c u l t to o b t a i n . The o n l y " n a t u r a l " m o r t a l i t y I was a b l e t o r e c o r d was a male k i l l i n g and e a t i n g two o f a l i t t e r o f t h r e e 40 - 50 pound k i t t e n s i n F e b r u a r y , 1966. He was e n c o u n t e r e d a t the second k i l l and c a p t u r e d ; the mother and s u r v i v i n g l i t t e r m a t e were a l s o c a p t u r e d . Young and Goldman (1946) s t a t e t h a t the male " w i l l devour i t s own y o u n g " b u t how p r e v a l e n t t h i s may be i s n o t known; t h i s was the o n l y o c c u r r e n c e o f c a n n i b a l i s m e n c o u n t e r e d i n t h i s s t u d y . C a n n i b a l i s m may be one form o f d e n s i t y - d e p e n d e n t b e h a v i o r a c t i n g to r e g u l a t e numbers. The f i r s t s i x months o f l i f e a r e p r o b a b l y q u i t e c r i t i c a l , p a r t i c u l a r l y a f t e r the k i t t e n s a r e t a k e n from the den where t h e y were b o r n . The female must n e c e s s a r i l y l e a v e them u n a t t e n d e d w h i l e she h u n t s . We have e v i d e n c e the young may be l e f t a l o n e f o r as l o n g as two days w h i l e the female h u n t s . Under t h e s e c i r c u m s t a n c e s they a r e q u i t e s u s c e p t i b l e to p r e d a t i o n as w e l l as a c c i d e n t s , and i n extreme i n s t a n c e s , s t a r v a t i o n . A n o t h e r c r i t i c a l p e r i o d appears to be the f i r s t few weeks a f t e r the young become s e l f - s u f f i c i e n t . T h i s o c c u r s (at l e a s t f o r t h o s e documented) i n w i n t e r . Some young l i o n s have d i f f i c u l t y i n s t a l k i n g l a r g e r p r e y a n i m a l s s u c c e s s f u l l y 29 and some appear inept i n k i l l i n g once they have made a successful stalk. These individuals must r e l y to a greater extent on lesser prey species. In some winters small mammals are i n short supply and I believe some young lions may starve. Mortality other than that recorded undoubtedly does occur. Joe Blackburn, C h a l l i s , Idaho, and Wayne England, North Fork, Idaho, told me of finding dead l i o n s . Mr. Blackburn, while hunting lions on the Middle Fork of the Salmon River, found two 20 pound kittens with crushed s k u l l s . He speculated that eagles might have been responsible for these deaths. Mr. England found the carcass of a mature male at the base of a c l i f f on the main Salmon River. I examined this cat's s k u l l and found i t to be fractured. I believe that some lions do suffer i n j u r i e s , some probably f a t a l , i n attacking elk. Elk, as are deer and other prey species, are attacked i n extremely rough t e r r a i n , and the chances of the l i o n i t s e l f being injured are good. Gaishwiler and Robinette (1957) report finding the s k u l l of a l i o n which had a piece of c u r l l e a f mountain mahogany wood penetrating the brain cavity. They speculated the cat impaled i t s e l f on the s t i c k during v i o l e n t action, such as an attack on a prey animal. These authors also found the decaying carcasses of a mule deer and large l i o n l ying together. The l i o n apparently died of a broken neck sustained i n the struggle. Old age may contribute s i g n i f i c a n t l y to mortality i n the Big 30 C r e e k p o p u l a t i o n . T h e r e i s e v i d e n c e t h a t a r t h r i t i s a t t a c k s o l d males ( I . McT. Cowan, p e r s . comm.). Young and Goldman (1946) s t a t e t h a t o l d a n i m a l s a r e u n a b l e to k i l l e f f e c t i v e l y and s t a r v e . Some o l d - a p p e a r i n g a n i m a l s i n t h i s s t u d y had s e v e r l y worn and b r o k e n t e e t h . T h e i r a b i l i t y t o k i l l l a r g e p r e y a n i m a l s u n d o u b t e d l y was i m p a i r e d . D i s p e r s a l . Marked l i o n s k i l l e d i n o t h e r a r e a s and the i n c i -dence o f t r a n s i e n t s on the s t u d y a r e a s u g g e s t t h a t i m m i g r a t i o n and e m i g r a t i o n a r e i m p o r t a n t f a c t o r s i n m a i n t a i n i n g s t a b l e p o p u l a t i o n s i z e . Two young a d u l t males marked on the s t u d y a r e a have been s h o t by h u n t e r s more t h a n 100 m i l e s d i s t a n t . A young a d u l t female was k i l l e d some 60 m i l e s from where she was marked. The g r e a t e s t p e r c e n t a g e o f the t r a n s i e n t s c a p t u r e d d u r i n g the s t u d y have been younger i n d i v i d u a l s , s u g g e s t i n g t h e y have n o t y e t s e t t l e d on a t e r r i t o r y . O t h e r F a c t o r s . O t h e r f a c t o r s a c t i n g to s t a b i l i z e the p o p u l a t i o n may i n c l u d e d i s e a s e and p a r a s i t e s . R a b i e s i s the o n l y . S e r i o u s d i s e a s e known t o a f f e c t w i l d l i o n s (Young, and Goldman, 1946). No e c t o p a r a s i t e s were found on any o f the l i o n s h a n d l e d i n t h i s s t u d y , b u t Young and Goldman (1946) r e p o r t s e v e r a l s p e c i e s o f t i c k s commonly found on m o u n t a i n l i o n s . Tapeworms ( E c h i n o c o c c u s  g r a n u l o s u s ) were c o l l e c t e d from the d r o p p i n g s o f one male i n t h i s s t u d y . The e f f e c t o f p a r a s i t e s on p o p u l a t i o n numbers i s p r o b a b l y n o t g r e a t . I n t r a s p e c i f i c b e h a v i o r has been shown t o be an i m p o r t a n t f a c t o r i n the s e l f - r e g u l a t i o n o f a n i m a l numbers. In d i s c u s s i n g t e r r i t o r i a l i t y , E l t o n (1950) s t a t e d t h a t s p e c i e s h a v i n g few e f f e c t i v e n a t u r a l enemies tend t o be s e l f - r e g u l a t o r y , and M u r i e (1944) and S t e n l u n d (1955) agreed t h a t t e r r i t o r i a l i t y would t e n d to c o n t r o l w o l f numbers. S c h a l l e r (1967) f e l t t h a t t i g e r p o p u l a t i o n s were s e l f - l i m i t e d and M i t c h e l l e t a l . , (1965) p r e s e n t d a t a w h i c h s u g g e s t l i o n s i n Kafue N a t i o n a l P a r k a r e s e l f - r e g u l a t e d . T e r r i t o r i a l i t y appears to be e x t r e m e l y i m p o r t a n t i n r e g u l a t i n g numbers o f m o u n t a i n l i o n s i n the Idaho P r i m i t i v e a r e a . The a c t u a l r e g u l a t i n g mechanism o r mechanisms a c t i n g i n t h i s p o p u l a t i o n a r e n o t known, though the i m p o r t a n c e o f m o r t a l i t y and d i s p e r s a l have a l r e a d y b e e n n o t e d . Home Ranges and T e r r i t o r i a l i t y L i m i t e d : i n f o r m a t i o n i s a v a i l a b l e on home range s i z e and t e r r i t o r i a l i t y i n the m o u n t a i n l i o n . Most d a t a i n the l i t e r a t u r e a r e based on s u b j e c t i v e o b s e r v a t i o n s by h u n t e r s . Young and Goldman (1946) l i s t some d i s t a n c e s t r a v e l e d by i n d i v i d u a l l i o n s b u t make no m e n t i o n o f home range s i z e . Palmer (1954) s t a t e s the home range c o v e r s "many s q u a r e m i l e s " and Bruce (1925) r e p o r t e d a range o f 100 s q u a r e m i l e s . O t h e r a u t h o r s c i t e s i m i l a r e x t e n s i v e r a n g e s . I n t e n s i v e s t u d i e s o f the l a r g e r s o l i t a r y F e l i d a e a r e few. Recent n o t a b l e e x c e p t i o n s a r e the work o f Saunders (1963a) w i t h l y n x (Lynx c a n a d e n s i s ) a n d S c h a l l e r (1967) w i t h t i g e r s ( P a n t h e r a  t i g r i s ) . Leyhausen (1959, 1965) has s t u d i e d the r o l e o f t e r r i t o r i a l i t y i n p o p u l a t i o n s o f f r e e - r a n g i n g d o m e s t i c c a t s . No s u c h s t u d y o f m o u n t a i n l i o n s has h e r e t o f o r e been u n d e r t a k e n . 32 D a t a c o n c e r n i n g movement and t e r r i t o r y s i z e and f u n c t i o n were o b t a i n e d t h r o u g h r e c a p t u r e s and by t r a c k i n g known i n d i v i d u a l s f o r a p e r i o d o f t i m e . Nine i n d i v i d u a l s t r a c k e d e x t e n s i v e l y and c a p t u r e d a t o t a l o f 47 t imes p r o v i d e d the b u l k o f the i n f o r m a t i o n . R e c a p t u r e s o f o t h e r i n d i v i d u a l s , w h i l e o f -a l e s s c o n c l u s i v e n a t u r e w i t h r e g a r d t o t h a t p a r t i c u l a r a n i m a l ' s r a n g e , s u p p o r t the e v i d e n c e g a i n e d from t h o s e r e c a p t u r e d more f r e q u e n t l y . I have u t i l i z e d the method o f D a l k e (1942), C r a i g h e a d and C r a i g h e a d (1956) and a l s o recommended by Mohr (1947) o f e n c l o s i n g a r a n g e a r e a by c o n n e c t i n g o u t l y i n g p o i n t s o f c a p t u r e or o b s e r v a t i o n . By t h i s method a r a n g e c a n be v i s u a l l y d i s p l a y e d on t o p o g r a p h i c and v e g e t a t i o n a l maps and r e l a t e d to t ime and a n i m a l a c t i v i t y . I n d i v i d u a l Ranges I n d i v i d u a l w i n t e r ranges were d e t e r m i n e d by p l o t t i n g o u t -l y i n g p o i n t s o f c a p t u r e o r o b s e r v a t i o n . " O b s e r v a t i o n " h e r e a p p l i e s to t h o s e i n s t a n c e s when an i n d i v i d u a l was t r a c k e d and s u b s e q u e n t l y c a p t u r e d . A d u l t M a l e s . The w i n t e r ranges o f t h r e e r e s i d e n t a d u l t males - - Numbers 3 , 7, and 18 - - a r e p l o t t e d i n F i g u r e 1. I n s u f f i c i e n t d a t a a r e a v a i l a b l e t o p l o t the range o f Number 10, the o t h e r mature male c o n s i d e r e d a r e s i d e n t . T h i s c a t was c a p t u r e d a t the mou*th o f B i g C r e e k ; t r a c k s i n d i c a t e h i s range l i e s u p s t r e a m from the mouth o f B i g C r e e k i n the M i d d l e F o r k d r a i n a g e . N i n e c a p t u r e s i n the t h r e e - y e a r p e r i o d p r o v i d e d the i n f o r m a t i o n u t i l i z e d i n d e l i m i t i n g the range o f Number 3. The w i n t e r range o f FIGURE 1 33 Winter Home Range of Three Resident Adult Males 34 this cat encompassed approximately 15 square miles. Number 18 was captured six times i n a two-year span. This male's range was confined to the Rush Creek drainage, a major tributary of Big Creek. The actual area occupied by No. 18 i n the drainage i s probably more than twice that indicated i n Figure 1. The range of Number 7 i s based on two captures i n subsequent years and on track data and i s more speculative. This male's winter range i s centered on lower Big Creek and downstream on the Middle Fork. The extent of his range i s nott known. Figure % shows that the ranges of these resident males do not overlap. The boundaries of the ranges of Number 3 and Number 18 may abut, but I am c e r t a i n they do not overlap. Adult males subsequently c l a s s i f i e d as transients, however, were captured i n a l l of the resident males' t e r r i t o r i e s (see Appendix). Adult Females. Ranges of four resident females are depicted i n Figure .2. Eight captures made over a three-year span established the range of Number 4 . Number 29 was captured f i v e times i n 1966-67; her d i s t i n c t i v e track, however, revealed she had been i n the area since the study began. Numbers 11 and 12 were captured three and fi v e times, r e s p e c t i v e l y 3 over a two-year period. The largest area occupied by a female was that of Number 4 i n 1965-66 -- approximately 15 square miles. The smallest was Number 29's i n 1966-67 -- about 3% square miles (Figure 4 ) . Two resident females are known to have changed the extent of t h e i r range i n d i f f e r e n t seasons and evidence suggests three ,1 n n n u c UI n U. H . RANGE of Nos. 11 — 12 ST^ R A N 6 E of No. 29 • 5*h V' J • : • •. 0 w..^' S7ODOAR0 C8£k / / ° _ * • Lookout Tower y • JDAHOCOUNTY • * "X kCK BU77J; ^ / SX* rt VYa.: g• GOAT WW £? O 1 fD !« to OP fD f y G S SA/p Island Tl ?d AGG/PAH V '  1 PEAK ^ _ £J .^o^ltoflt .tower" N West i j L f ^ ^ ^ ^ / | V '• ' E A G A N Scalei 1 inch = 2.5 miles Contour Interval 200 feet / MOUNTAIN^ v WUSON " rt \. MOUNTAIN ^ Ni fD to i—1 ro j ©lookout tower CO 36 others have done likewise„ Figure 3 shows the range of Number 4 for the three winter seasons. In 1964-65 she confined h e r s e l f to the eastern portion of the indicated range. She was accompanied by three kittens-of-the-year during this season. In 1965-66, s t i l l accompanied by the three kittens, she was captured at the further-most points i n Figure 3. The past year, again with small kittens-of- the-year, she confined h e r s e l f to the western portion of the indicated t e r r i t o r y . Similar data are available for female Number 29 (Figure 4). In 1965-66, this female had three kittens; alone i n 1966-67, she u t i l i z e d only about one-third of the previous year's range. Recapture data for Numbers 11, 12, and 16 are less conclusive, but the fact that these females were not recaptured i n c e r t a i n areas i n given years suggests that they also altered their ranges. Numbers 11 and 12 were captured early i n the season of 1965-66 i n the westermost portion of the range shown i n Figure 2. They were not recaptured i n 1965-66. Number 16 occupied the eastern portion of the Rush Creek drainage i n 1965-66. She was not recaptured i n 1966-67 and was subsequently c l a s s i f i e d a temporary resident. Numbers 11 and 12, d e f i n i t e l y residents, occupied the whole range depicted i n Figure 2 i n 1966-67. Figure 5 i l l u s t r a t e s the ranges occupied by three resident adult males and four resident adult females. The range of male Number 3 overlaps that of two females. Numbers 4 and 29. Females Number 11 and 12 resided i n the same t e r r i t o r y as male Number 18. FIGURE 3 37 Home Range of Female Number 4 In Three Winter Seasons Cofd'Meadows (uSFS) ( GOncwWWCJO h^5J{ / RANGE IN 19 6 5 - 66 .. R A N G E IN 1 9 6 6 - 6 7 Lookout Towtr OLD MOUNTAIN gkou. tower (, A ° PAPOOSE J t D A H Q C W N T Y POINT / lookout tower ko<lWjtowe£ • tiylor Ranch j J / SHEEP HOR MQ E4GAN POINT K . Ship Island n — " /.r?Av . K AGGIPAH J ; * J -J) \,MOUNTAIN »5*fl> I—I O a g Scales 1 inch = 2.5 miles Contour Interval 200 feet J -, Lookout tower , - ^a<~* , • CO 00 FIGURE 5 39 Winter Home Range of Three Resident Adult Males And Four Resident Adult Females 40 Female " X " ( T a b l e V) was i n male Number 7 ' s t e r r i t o r y i n 1966-67 b u t i t i s n o t known i f she was r e s i d e n t t h e r e . I t i s s t r e s s e d t h a t the b o u n d a r i e s p l o t t e d i n the f o r e g o i n g f i g u r e s must n o t be r i g i d l y i n t e r p r e t e d . B o u n d a r i e s were d e t e r m i n e d from c a p t u r e d a t a a n d , i n a few i n s t a n c e s , t r a c k d a t a and s u g g e s t home range e x t e n t . I am c e r t a i n the a c t u a l a r e a s u t i l i z e d by some l i o n s e x t e n d beyond t h a t i n d i c a t e d . I do b e l i e v e , however, t h a t t e r r i t o r i e s r e l a t i v e to each o t h e r a r e p r o p e r l y d e p i c t e d by the c a p t u r e d a t a . In t h i s r e s p e c t , the f a c t t h a t some l i o n s were n o t c a p t u r e d i n c e r t a i n a r e a s i s e q u a l l y as i m p o r t a n t as c a p t u r e d a t a on o t h e r i n d i v i d u a l s . Dasmann and Taber (1956) used t h i s type o f " n e g a t i v e " d a t a i n d e t e r m i n i n g home ranges o f d e e r . F u n c t i o n o f T e r r i t o r i a l i t y The male l i o n s r e s i d e n t i n the B i g C r e e k d r a i n a g e c l e a r l y e x h i b i t a s p a t i a l d i s t r i b u t i o n o f t e r r i t o r i e s . (I have adopted E t k i n ' s (1964) u n q u a l i f i e d use o f the term " t e r r i t o r y " ) . No d e f e n s e o f a t e r r i t o r y was n o t e d i n the s t u d y and t r a n s i e n t and tem-p o r a r y r e s i d e n t l i o n s , b o t h males and f e m a l e s , used t h e s e t e r r i t o r i e s f r e e l y . Female r e s i d e n t s , w h i l e e x h i b i t i n g E t k i n ' s d e f i n i t i o n o f t e r r i t o r i a l b e h a v i o r , s h a r e d the same a r e a w i t h o t h e r females„ These t e r r i t o r i e s were a l s o o v e r l a p p e d by t h o s e o f mature males ( F i g u r e 5 ) . S p a t i a l d i s t r i b u t i o n o f t e r r i t o r i e s s u g g e s t s some type o f i n t e r a c t i o n between i n d i v i d u a l s , u s u a l l y o f the same sex. D i c e (1952) s t a t e s t h a t s u c h a d i s t r i b u t i o n u s u a l l y r e s u l t s from a defense of t e r r i t o r i e s , although i t can occur purely as an e f f e c t of the unsocial behavior of the species. During 1965-66 i t became apparent that lions were avoiding close contact with one another. S t r i k i n g examples of this avoidance behavior, which I termed a "mutual avoidance reaction" (Hornocker, 1967), were recorded by tracking the animals i n snow. Mature males, both residents and transients, avoided not only other males but lone females and females with families. The same was true of a l l females. Social tolerance was exhibited only by males and females during the breeding season and by females and young during the period of juvenile dependency. Lack (1954) recognized the importance of avoidance behavior, stating "...dispersion i s primarily due to the avoidance of occupied or crowded ground by p o t e n t i a l s e t t l e r s , not to aggres-sive behavi or of those i n occupation." Tinbergen (1957) believes both attack and escape (avoidance) are involved. Numerous examples of avoidance recorded i n this study support Lack's view. Avoidance, however, was not limited to "potential s e t t l e r s " ; residents exhibited the same behavior. One s t r i k i n g example involving males i s worthy of mention. On January 10, 1967, we captured a young unmarked male i n the t e r r i t o r y of resident male Number 3. This young male had k i l l e d an elk the previous day, had stayed at the k i l l , and was captured there. Tracks indicated a large male had passed within 50 yards of the young male and i t s k i l l the same day we captured the young male. The following day we tracked the large 42 male and captured him some three miles distant. It was Number 3, the male resident on the area. He had made no attempt to challenge the young male transient; i t appeared he purposely avoided contact once he became aware of the young male,'s presence. The same areas were used by d i f f e r e n t individuals but never at the same time -- lions were spaced i n time as well as area. "Scrape" or "scratch" marks appear important i n this regard. Lions urinate and frequently defecate on top of these marks --an olfactory as well as v i s u a l mark i s made. A l l l i o n s , but p a r t i c u l a r l y the males, make these marks i n t r a i l s , on high ridges 9 and at l i o n "crossings"; some permanent "stations" occur i n each t e r r i t o r y . Both males and females invariable v i s i t these si t e s and o r d i n a r i l y t r a v e l much the same route, whether hunting or seemingly j u s t traveling. On a number of occasions an animal tracked to one of these sites abruptly changed i t s apparent course, sometimes retracing i t s route for a considerable distance. Invariably i t was found that another l i o n or family of lions was i n the area. Leyhausen and Wolff (1959) found that free-ranging domestic cats shared pathways and hunting grounds but emphasized that common use did not mean simultaneous use. The cats avoided encounters by keeping to a more or less d e f i n i t e time table. These cats spaced themselves by v i s u a l contact but Leyhausen believes that mammals which l i v e i n densely grown habitats u t i l i z e olfactory markings to prevent encounters. These marks function "rather l i k e 43 railway signals"., serving to n o t i f y newcomers of the presence of another animal. Each i n d i v i d u a l , before passing such a mark, regularly covers i t - w i t h his own, thus "closing the section" (Leyhausen, op_„ c i t . ) . Leyhausen's observations might well have been made on the lions i n this study„ It should be pointed out that I arrived at my conclusions concerning t e r r i t o r i a l i t y and function of the scrape marks before I knew about Leyhausen's work. A further function of t e r r i t o r i a l i t y -- i n a sense of both time and space -- appears to be greater success i n securing large prey animals -- mountain lions must employ st e a l t h to place them-sleves within s t r i k i n g distance. The chances of success i n an area already hunted or being hunted by another i n d i v i d u a l are much less than i n an area where prey animals are undisturbed. Crook (196.5) believes this i s a major factor i n the t e r r i t o r i a l i t y of nesting kingfishers. He states " . . . i n d i v i d u a l methods of hunting probably ensure greater success per b i r d than group attacks on e a s i l y alarmed f i s h shoals could allow." T e r r i t o r i a l i t y also results i n greater f a m i l i a r i t y with a l o c a l i t y and i t s topography; this allows a predator to u t i l i z e an area's food resources more e f f i c i e n t l y (Tinbergen, 1957). The type of non-aggressive t e r r i t o r i a l behavior exhibited by the mountain lions i n this study has been reported for a number of other species. Leyhausen documented i t thoroughly for domestic cats„ Schaller (1967) found resident tigers i n India tolerant of transients, but speculated that some males might 44 defend a t e r r i t o r y against other males. He f e l t a s e l f -l i m i t i n g trend was operating i n the population on the l o c a l l e v e l , "perhaps based on i n t r a s p e c i f i c intolerance when meeting or sharing a k i l l and, more subtly, on various v i s u a l and olfactory signals l e f t i n the environment." Wright (1960) found d i f f e r e n t prides of lions i n A f r i c a hunting the same general area without apparent f r i c t i o n . Hunting c i r c u i t s were regularly used but there was no evidence of defended t e r r i t o r i e s . Errington (1963) reported that minks withdrew from mink-crowded places i n spite of superabundances of food; s o c i a l intolerances worked to keep mink populations spread out. Hawley and Newby (1957) found no defense of a t e r r i t o r y i n marten and s p a t i a l relationships were achieved by strong a n t i s o c i a l behavior. Craighead and Craighead (1956) report an "automatic cooperative adjustment" i n birds of prey where spacing was achieved by tolerant but unsocial behavior. Similar behavior i s reported for co a t i bands i n Panama (Kaufmann, 1962) and for various primate bands (Hall, 1965; Southwick, 1962). Here the function of bands was sim i l a r to that of the in d i v i d u a l of a s o l i t a r y species. Summing up, the primary function of t e r r i t o r i a l i t y i n the mountain l i o n population appears to be a s p a t i a l d i s t r i b u t i o n of individuals. This spacing, brought about without apparent conflict*, acts to l i m i t population size (see Carrick, 1963). Further, this behavorial mechanism provides the c a p a b i l i t y of adjusting these s p a t i a l arrangements with respect to changing environmental 45 c o n d i t i o n s , t o the p r e s e n c e o f o t h e r l i o n s , and t o the i n d i v i d u a l s ' c h a n g i n g r e p r o d u c t i v e s t a t u s . Such a b e h a v i o r a l mechanism appears n e c e s s a r y to the s u r v i v a l o f p o p u l a t i o n s o f s o l i t a r y , s p e c i a l i z e d p r e d a t o r y s p e c i e s . A s o l i t a r y p r e d a t o r must depend on i t s p h y s i c a l w e l l - b e i n g t o s u r v i v e . F i g h t i n g i n the d e f e n s e o f a t e r r i t o r y has been r e p o r t e d f o r more g r e g a r i o u s p r e d a t o r s , s u c h as w o l v e s ( M u r i e , 1944; Mech, 1966; Cowan, 1947); T i n b e r g e n (1957) r e p o r t s the same b e h a v i o r i n Eskimo h u s k i e s . The " m u t u a l a v o i d a n c e " mechanism appears t o have e v o l v e d as a much more e c o n o m i c a l means o f s p a c i n g s o l i t a r y i n d i v i d u a l s . F i g h t i n g ] may o c c u r a t t imes b u t I b e l i e v e i t i s an e x t r e m e l y r a r e o c c u r r e n c e . 46 PREY POPULATIONS Numbers Counts were made of prey species sighted throughout the three f i e l d seasons. The counts (Table VI) were confined to big game species, namely e l k 3 mule deer, and bighorn sheep. Mountain goats were sighted on several occasions but are not considered an important prey species i n the Big Creek drainage. Some repetitions are unavoidable, p a r t i c u l a r l y with, bighorn sheep, and the figure obtained for this species probably represents an observed population of no more than one-third that number. Results of the a e r i a l counts are presented i n Table VII. Differences i n the r a t i o of deer to elk observed on the ground and from the fixed wing airplane, have been consistent. On the ground the r a t i o of deer to elk observed has been 5 : 3 , 4 : 3 , and 6,9 : 3 during the 1964-65 9 1965-66, and 1966-67 seasons respectively. From the a i r this r a t i o has been reversed i n favor of elk 1 : 3 deer to elk i n 1965-66 and 0 .85 : 3 i n 1966-67. This was expected -- elk are much more e a s i l y observed from the a i r . Bighorn sheep are extremely d i f f i c u l t to count from the a i r i n this t e r r a i n and are not considered i n the population analyses, A helicopter census of the study area was conducted by men of the Idaho Fish and Game Department A p r i l 23 to A p r i l 26, 1967. The count from this more maneuverable a i r c r a f t was 848 elk and 466 deer. The ground counts (Table VI) show a steady increase i n the Table VI Species Elk Deer Sheep T o t a l Cumulative Numbers and C l a s s i f i c a t i o n of Big-Game Prey Animals Observed, Big Creek-Middle Fork Drainage 1964-67 No. D i f f . Days Animals Sighted 1964- 1965- 1966-1965 1966 1967 69 42 66 61 25 20 74 93 24 Cumulative T o t a l of Animals Recorded 1964- 1965- 1966-1965 1966 1967 599 1019 460 612 838 824 1946 327 454 Percent of T o t a l Prey Species Recorded 1964- 1965- 1966-1965 1966 1967 29 49 22 34 47 19 25 60 15 T o t a l No. C l a s s i f i e d 1964= 1965- 1966-1965 1966 1967 160 181 98 518 677 125 648 976 233 2078 1763 3238 100 100 100 Species E l k Deer Sheep No. of Males and % of T o t a l 1964- 1965- 1966-No. of Females and % of T o t a l 1964- 1965- 1966-No of J u v e n i l e s and % of T o t a l 1964- 1965- 1966-1965 (%) 1966 (%) 1967 (%) 1965 (%) 1966 (%) 1967 (%) 1965 (%) 1966 (%) 1967 (%) 41 (25) 45 (9) 49 (8) 22 (12) 72 (11) 126 (12.3 18 (18) 30 (24) 66 (28) 105 (66) 372 (72) 467 (72) 14 (9) 101 (19) 132 (20) 129 (71) 464 (68) 631 (65) 30 (17) 141 (21) 219 (22.5) 61 (62) 74 (60) 136 (58) 19 (20) 21 (16) 34 (14) 48 number of elk i n the Big Creek drainage, a sharp increase i n deer i n 1966-67, and stable numbers of bighorn sheep. The increase i n elk i s supported by the a e r i a l counts the past two years. I believe that the large increase i n deer the past season is a response to two extremely mild winters. This also explains the smaller number observed i n 1965-66 -- deer remained high and scattered through the winter. Increased s u r v i v a l i n 1965-66, possible higher productivity, and good su r v i v a l of fawns i n 1966-67 are offered as factors i n the apparent population increase. Table VII Results of A e r i a l Census Big Creek Drainage 1966 and 1967 Type of A i r c r a f t 1966 1967  Elk Deer Elk Deer Fixed-Wing 560 188 691 195 Helicopter --- . - - - 848 466 These populations are subjected to lo c a l i z e d , moderately heavy human hunting pressure. Idaho Fish and Game Department hunter questionnaire data established a hunter k i l l for 1966 of 242 elk and 260 mule deer. Hunting regulations for deer have varied, a f f e c t i n g the k i l l , but the k i l l figures have remained r e l a t i v e l y unchanged for the past several years (D. Neider, pers. comm.). It i s d i f f i c u l t to esta b l i s h a t o t a l population size for such an area. The data obtained from counts made on the ground 3 49 however, combined with those from a e r i a l censuses allow a reasonably accurate estimation of game animal numbers. The number of elk observed from the helicopter i n 1967 --848 -- must be considered an absolute minimum number. It i s generally agreed that a e r i a l observers seldom see a l l the animals on a census area (Buechner, et a l . , 1951; Watson and Scott, 1956). This i s e s p e c i a l l y true i n rugged, timbered t e r r a i n such as that on the study area. Censuses were made during spring "green-up" when game animals had largely moved to open south-facing slopes, but observations made on the ground at the same time indicated many animals were s t i l l i n the timbered areas. Lovaas et ajL. (1966) found that the effectiveness of counts made i n the Sun River area i n Montana depended on the number of elk found i n the open f o o t h i l l segment of the winter range. From 1950 through 1960, a e r i a l counts of over 3,000 elk were made i n the Sun River area during seven winters and 70 to 82 percent of the elk seen on each count were on the open f o o t h i l l s . During two winters of the 10-year period fewer than 3,000 elk were counted; on those counts and' counts made after 1960 where the highest count was 2,051 elk, only an average of 57 percent of the elk were on the open h i l l s . The herd was l i g h t l y harvested and no immigration was noted. The authors assumed that no less than 3,000 elk were present after 1960. Terrain and conditions c i t e d by Lovaas et. a_l. , are similar to those: i n the Big Creek area. The highest of the counts below 3,000 obtained by these Montana workers was 2,051; one-third of 50 the elk known to winter i n the area were not seen. Judging from results of this Montana work and from my observations of the number of elk inhabiting timbered areas at the time of the census, I believe at least one-third of the elk i n the Big Creek area were not observed from the a i r . Adding one-third to 848 would place the t o t a l population estimate of elk at 1,130 i n the Big Creek area i n the spring of 1967. When the 1966 data are treated i n the same manner, except using the highest count, i n this case the ground count figure, an estimate of 816 i s obtained. The estimate for 1965 becomes 799. I believe this i s a conservative estimate. Other workers believe that no more than one-half the animals present on an area such as this are seen from the a i r ; Erickson et a l . (1963) counted only one-half of the known bears known to be i n a p a r t i c u l a r area, i n spite of l i g h t vegetative cover. A e r i a l counts of deer offe r no data for comparison with those counts made on the ground. However, i f we consider that deer are no more observable on the ground than are elk, then the same adjustments made to elk numbers could be made to those for deer. I believe this i s a v a l i d procedure -- deer are no more e a s i l y seen than elk. This assumption i s further strengthened by the fact that the cumulative count of elk made on the ground i n 1966-67 was less than those actual numbers observed at one time from the helicopter. The population estimates, then, become 1 ,359, 1 ,099, and 2,595 for the three years. The count and estimate for 1966 is too low„ The winter of 1965-66 was extremely mild and deer remained h i g h and s c a t t e r e d t h r o u g h o u t the w i n t e r . T a b l e V I I I p r e s e n t s b o t h c u m u l a t i v e ground c o u n t s and a c t u a l a e r i a l c o u n t s and the a d j u s t e d p o p u l a t i o n e s t i m a t e s o f d e e r and e l k f o r the t h r e e - y e a r p e r i o d . I t must be c l e a r l y u n d e r s t o o d t h a t the a d j u s t e d f i g u r e s a r e e s t i m a t e s based on a e r i a l t r e n d c o u n t s and on c u m u l a t i v e c o u n t s made on the g r o u n d . I b e l i e v e the e s t i m a t e s f o r e l k a r e h i g h l y a c c u r a t e . The 1967 e s t i m a t e f o r d e e r may be too h i g h . The d e e r p o p u l a t i o n i n c r e a s e d m a r k e d l y i n 1967 b u t i t may n o t have r i s e n t h i s much. Sheep numbers have remained s t a b l e f o r the t h r e e - y e a r p e r i o d . As s t a t e d , r e p e t i t i o n s a r e u n a v o i d a b l e i n c o u n t i n g t h i s s p e c i e s ; I b e l i e v e a p o p u l a t i o n e s t i m a t e o f 150 i s r e a s o n a b l y a c c u r a t e . T a b l e V I I I A c t u a l Counts and A d j u s t e d P o p u l a t i o n E s t i m a t e s o f E l k and D e e r , B i g C r e e k D r a i n a g e 1964 - 67 E l k 1964-65 1965-66 1966-67 Deer 1964-65 1965-66 1966-67 Ground c o u n t 599 612 838 1,019 824 1,946 F i x e d - w i n g a e r i a l c o u n t 560 691 188 195 H e l i c o p t e r a e r i a l c o u n t 848 466 A d j u s t e d 799 816 1,130 1,359 1,099 2,595 52 Age and Sex Composition Table VI presents the numbers of elk, deer, and sheep c l a s s i f i e d as to age and sex during each of the three winters. Age c l a s s i f i c a t i o n was limited to adult-juvenile categories. Light and weather conditions and distance from some animals prevented c l a s s i f i c a t i o n of a l l game animals counted. It i s seen i n Table VI that the percentage of c a l f elk and fawn deer i n t h e i r respective populations rose from 9 to 20 percent and from 17 to 22.5 percent, respectively, during the three-year period. This i s better expressed i n terms of calf-cow and fawn-doe ratios (Table IX). These data further support the contention that these populations have increased. Figures i n Tables VI and IX are a c t u a l l y s u r v i v a l rates of juvenile elk and deer to "yearling" age and thus express e f f e c t i v e reproduction rather than herd fecundity. Cumulative c l a s s i f i c a t i o n counts were made throughout the f i e l d season, but by far the greatest majority of animals were c l a s s i f i e d i n the spring. The r e l a t i v e percentages of males and females for both elk and deer have remained f a i r l y constant at about 70 percent females and 9-12 percent males. An exception i s the percentage -- 25 --of b u l l elk recorded i n 1964-65. One possible explanation of this i s the small number of elk c l a s s i f i e d i n 1964-65; 8 and 9 percent were recorded for the two subsequent years when a great many more elk were c l a s s i f i e d . I f e e l the percentages for both b u l l elk and 53 buck deer are low; these adult males tend to remain i n higher, rough areas where observations are more d i f f i c u l t . Table IX Number of Calf Elk and Fawn Deer per 100 Adult Female* Elk and Deer Big Creek Drainage 1964-67 1964-65 1965-66 1966-67 Elk . .13 - 27 28 Deer 23 30 34 * Female elk and deer 1% years and older Physical and N u t r i t i o n a l Condition Fourteen big-game animals were k i l l e d i n the 1966-67 season i n an attempt to sample the n u t r i t i o n a l state of the populations. Five elk and nine deer were shot from December 16, 1966, to May 3 , 1967, and th e i r physical condition was assessed. In a l l cases the f i r s t animal presenting i t s e l f was collected -- this was done i n an e f f o r t to randomize the sample. The animals shot, th e i r age, sex, the date k i l l e d , and physical condition are l i s t e d i n Table X. Laboratory analyses of the femur marrow showed that of the f i v e elk, three were i n good condition, two were poor; six deer were i n good condition, and three were poor. In this random c o l l e c t i o n , nine of 14 animals, or 64 percent, were i n good physical condition. 54 Table X Elk and Deer Specimens Collected at Random 1966-67 Specimen Number Species Age Sex Date K i l l e d 1 elk 2% F 12-16-66 2 elk 4i> F 1-17-67 3 deer 2% F 1-25-67 4 deer fawn M 2-9-67 5 deer 5% M 2-24-67 6 deer 7% M 2-25-67 7 deer 5% M 2-27-67 8 elk c a l f F 3-2-67 9 elk Ih F 3-2-67 10 elk 3% F 3 - 3 - 6 7 11 deer 1% M 3-22-67 12 deer fawn F 4-1-67 13 deer 8% F 4-2-67* 14 deer 4% F 4 - 3 - 6 7 Physical Condition good good good good good poor good poor poor good poor poor good good 55 MOUNTAIN LION KILLS K i l l s made by lions were located during the course of capturing and marking and other a c t i v i t i e s . Lions were encountered at some k i l l s , while tracks and sign, at other carcass remains gave i n d i c a t i o n of l i o n k i l l s . If sign was not conclusive, the k i l l was not considered to have been made by l i o n s . A "probable k i l l " category, used i n 1964-65 and 1965-66, was discontinued the past season. A l l k i l l s considered i n this paper are animals d e f i n i t e l y k i l l e d by l i o n s . Elk and deer comprise by far the greatest share of the l i o n s ' winter d i e t . Bighorn sheep do not appear to constitute even a small part of this d i e t despite the fact the area supports a sizable population. Only two k i l l s of sheep were recorded i n the three-year period. Both were ewes, one i n extremely poor condition, and both were k i l l e d by the same l i o n , a female. Sheep i n this area appear well able to cope with l i o n predation; I f e e l the numbers taken by lions are i n s i g n i f i c a n t . Tables XI and XII summarize the age, sex, and physical condition of 44';.elk and 39 deer k i l l e d by lions i n the three seasons. Thirty-three, or 75 percent of the elk were i n the "young" or "old" age classes -- 1% years or less and 9% years or older. The data for deer are somewhat sim i l a r -- 20 of 35 deer for which age was determined s or 57 percent were young or old. In both cases, far more young animals were k i l l e d . This may be attributed to several d i f f e r e n t factors, and possibly a combination of factors. Ratios Table XI Age, Sex, and Physical Condition of 44 Elk Killed by Mountain Lions 1964-67 Sex Physical Condition Total Number Percent of Not Not Age in Age Class Total Ki l l Male Female Determined Good • Poor* Determined Calf (6-12 Mo.) 22 50 6 8 8 7 14 1 1- 1/2 5 11 3 2 - 2 2 1 2- 1/2 4 9 2 2 - 4 - -3- 1/2 4 9 1 3 - 4 5-1/2 3 7 1 2 - 1 1 1 9-1/2 3 7 - 3 - 1 1 1 15 _5_ _7_ _1_ _2__ _1_ _2_ -TOTAL 44 100 14 22 8 20 20 4 *Includes animals classified as "Fair" in 1966-67 (see text). Table XII Age, Sex, and Physical Condition of 39 Deer K i l l e d by Mountain Lions 1964-67 Sex Age Fawn (6-12 Mo) 1- 1/2 2- 1/2 3- 1/2 4- 1/2 6-1/2 8-1/2 '9-1/2 10+ Not Determined Total Number i n Age Class 14 3 2 5 2 3 2 4 4 Percent of Total K i l l 40 6 14 6 8 6 12 Not Male Female Determined 2 3 2 4 3 1 3 1 10 Physical Condition Not Good Poor* Determined 9 1 TOTAL 39 100. 12 11 16 16 16 * Includes animals c l a s s i f i e d as " f a i r " i n 1966-67 (see.text) ** Not included i n "Percent of Total K i l l " 58 of fawns and calves to adult animals have increased (Table VI)--more young animals were available to the lions the past season. There i s no question that these inexperienced individuals are less l i k e l y to elude a predator. It appears the lions select smaller elk. Twelve of 16 elk k i l l e d the past season were calves, and 50 percent of the three-year k i l l was calves. Their apparent reluctance to attack b u l l s over \\ years of age supports this view. In addition, young animals as well as very old, are the f i r s t to show effects of malnutrition, making them more susceptible to predation. The data indicate no prevalence of one sex over the other i n the k i l l s of younger elk and deer, nearly equal numbers of males and females under 1% years being taken. Seven buck deer and nine does over 2% years have been recorded indicating a r e l a t i v e l y greater proportion of bucks are taken by lio n s . In elk, however, i t appears that more mature cows than b u l l s are k i l l e d . Twelve cows 2% years and older were recorded and only f i v e b u l l s i n these age classes. Cows far outnumber b u l l s (Table VI) but I do not believe that this apparent s e l e c t i v i t y i s a function of a v a i l a b i l i b u l l s more often place themselves i n vulnerable positions, with respect to l i o n predation s than do the cows. Table XIII presents the r e l a t i v e numbers of adult males and females and juveniles of both sexes i n the elk and deer populations and the percent each class comprised i n the t o t a l l i o n k i l l . Juveniles and adult males were taken i n greater numbers with respect to th e i r numerical 59 a v a i l a b i l i t y -- a d i r e c t r e s u l t of t h e i r g r e a t e r v u l n e r a b i l i t y . As mentioned, however, b u l l e l k o l d e r than 2\ years were r e l a t i v e l y immune to a t t a c k . Table X I I I Composition of the Big Creek E l k and Deer Po p u l a t i o n s and the Percent Represented by Each C l a s s i n the T o t a l L i o n K i l l E l k P ercent Occurrence'' Represented i n i n T o t a l P o p u l a t i o n L i o n K i l l Deer Adult.Males**" 14 A d u l t Females** 70 J u v e n i l e s 1.6 18 32 50 Occurrence* i n P o p u l a t i o n 12 68 20 Percent • Represented i n T o t a l L i o n K i l l 30 28 42 * Three-year average expressed i n terms of 100 animals ** Animals 1% years and o l d e r . P h y s i c a l C o n d i t i o n of K i l l s Table XI shows that 20 e l k were co n s i d e r e d i n good p h y s i c a l c o n d i t i o n and 20 were i n poor c o n d i t i o n ; Table X I I shows 16 and 16 deer, r e s p e c t i v e l y 3 i n these c a t e g o r i e s . In 1966-67, specimens of the femur marrow were taken from a l l l i o n - k i l l e d animals and from those shot i n a randomly c o l l e c t e d sample. These specimens were preserved i n f o r m a l i n and l a t e r submitted to ether e x t r a c t i o n analyses f o r f a t content. Analyses of specimens preserved i n t h i s 60 manner r e s u l t e d i n a d r y - w e i g h t e x p r e s s i o n o f f a t c o n t e n t . S i n c e a h i g h - f a t c o n t e n t i s found i n a l l samples when e x p r e s s e d on a d r y - w e i g h t b a s i s ( B i s c h o f f , 1954).,, c o m p a r i s o n to f i g u r e s o b t a i n e d from f r e s h specimens i s n e c e s s a r y i n o r d e r t o g e t a t r u e r p i c t u r e o f a n i m a l c o n d i t i o n . These d a t a , w h i c h s e r v e d as a c o n t r o l , were s u p p l i e d by Mr. J e r o l d T h i e s s e n , B i o l o g i s t , Idaho F i s h and Game D e p a r t m e n t . The f r e s h samples were f i r s t s u b j e c t e d to e t h e r e x t r a c t i o n a n a l y s i s and a w e t - w e i g h t p e r c e n t a g e o f f a t o b t a i n e d . They were t h e n d r i e d and the same a n a l y s i s p e r f o r m e d . A R e g r e s s i o n a n a l y s e s was p e r f o r m e d on t h e s e d a t a and the c o r r e c t i o n f a c t o r a p p l i e d to the d r y - w e i g h t a n a l y s e s o b t a i n e d from 33 l i o n - k i l l e d d e e r and e l k and 14 a n i m a l s s h o t i n a randomly c o l l e c t e d sample i n 1966-67. T h i s adjustment r e s u l t s i n a f i g u r e r e p r e s e n t i n g w e t - w e i g h t f a t c o n t e n t , a more p r o p e r e s t i m a t e o f a n i m a l c o n d i t i o n ( B i s c h o f f , 1954). T a b l e XIV p r e s e n t s a c o m p a r i s o n o f the r e s u l t s o f the d r y -w e i g h t a n a l y s e s , the a d j u s t e d a n a l y s e s , and the f i e l d assessments i n d e t e r m i n i n g p h y s i c a l c o n d i t i o n o f the a n i m a l s k i l l e d i n 1966-67. Cheatum (1949) found t h a t e x t e n s i v e w i t h d r a w a l s ( r e d u c t i o n o f o v e r 50 p e r c e n t ) from the marrow f a t o f the femur does n o t o c c u r u n t i l the f a t d e p o s i t s under the s k i n and around the v i s c e r a and body c a v i t i e s a r e e x h a u s t e d . T h e r e f o r e , a n i m a l s w i t h 50 p e r c e n t o r more f a t irt the femur marrow wete c o n s i d e r e d , i n " g o o d " c o n d i t i o n , those below 50 p e r c e n t i n " p o o r " p h y s i c a l c o n d i t i o n . The d r y - w e i g h t a n a l y s e s , as e x p e c t e d , showed a h i g h 61 p e r c e n t a g e o f a n i m a l s i n good c o n d i t i o n . When the c o r r e c t i o n f a c t o r , o b t a i n e d from the s t a t i s t i c a l a n a l y s i s o f the c o n t r o l s p e c i m e n s , was a p p l i e d to t h e s e f i g u r e s t o e x p r e s s f r e s h - w e i g h t f a t p e r c e n t a g e s , i t was shown t h a t o n l y 15 o f 33 l i o n - k i l l e d a n i m a l s and 9 o f 14 randomly c o l l e c t e d d e e r and e l k were i n good c o n d i t i o n . A l l a n i m a l s j u d g e d i n f a i r c o n d i t i o n i n the f i e l d were shown t o be below 50 p e r c e n t marrow f a t and thus were i n p o o r c o n d i t i o n , , I f t h e s e a r e c o n s i d e r e d " p o o r " i n the f i e l d d e t e r m i n a t i o n s , t h e n the a d j u s t e d a n a l y s e s and the f i e l d judgments c o r r e s p o n d q u i t e c l o s e l y . T a b l e XIV D e t e r m i n a t i o n o f P h y s i c a l C o n d i t i o n o f 33 E l k and D e e r K i l l e d by M o u n t a i n L i o n and 14 Randomly C o l l e c t e d E l k and Deer 1966-67 Femur Marrow A n a l y s e s  L a b o r a t o r y A n a l y s e s  P e r c e n t F a t Dry Weight Good P o o r P e r c e n t F a t A d j u s t e d Good Poor F i e l d D e t e r m i n a t i o n s Good F a i r Poor M o u n t a i n L i o n K i l l s 25 8 15 18 17 8 Random C o l l e c t i o n 12 11 The c l o s e n e s s o f the f i e l d d e t e r m i n a t i o n s to the a d j u s t e d a n a l y s e s o f femur marrow f a t c o n t e n t i n 1966-67 s u p p o r t s the v a l i d i t y o f the f i e l d d e t e r m i n a t i o n s o f a n i m a l c o n d i t i o n made i n 1964-65 and 1965-66„ The breakdown of the f i e l d determinations for 1964-65 and 1965-66 are presented i n Table XV along with the adjusted analyses for 1966-67 -Table XV Physical Condition of 72 Elk and Deer K i l l e d by Mountain Lions, 1964-67 Elk Deer Good Poor Good Poor 1964- 65 5 4 6 1 1965- 66 8 7 4 4 1966- 67 7 9 8 9 Total 20 20 18 14 63 FREQUENCY OF KILLING It i s d i f f i c u l t to e s t a b l i s h the number of consecutive k i l l s made by an i n d i v i d u a l l i o n i n a given period of time; data on this aspect are scanty. Number 4 and her three large (70 lb) kittens k i l l e d four deer i n an 18-day period i n 1965-66, Number 7 C and her three large kittens k i l l e d one elk i n 12 days. We have evidence that some cats go without k i l l i n g a big-game animal for more than six to eight days., and I suspect for some lions this i n t e r v a l i s longer, I believe that a mature l i o n i n the Big Creek area k i l l s one deer every 10 to 14 days during the winter. This i n t e r v a l i s longer when elk are k i l l e d and I am c e r t a i n i t i s considerably longer i n summer when many smaller prey species are available. As Schaller (1967) points out, however, the frequency of k i l l i n g depends on the size and species of the prey, on the numbers of animals eating from the remains, and on other factors, making estimates of food consumption based soley on the number of animals k i l l e d of s l i g h t value. Mountain lions can eat a large quantity of meat i n a short time. On two occasions males were surprised at freshly k i l l e d elk on which they had fed on only one hind quarter. Both cats had eaten, i n no more than one night p r a c t i c a l l y the whole quarter, judged to be 30 to 40 pounds of meat. Schaller (1967) states that tigers can eat up to o n e - f i f t h of t h e i r body weight i n a short period of time. The number of pounds ingested i n a short time, however,, give l i t t l e i n d i c a t i o n of the animal's need on a long-64 term basis. Cats appear able to adapt to a feast or famine regime. Golley e_t a_l. (1965) found bobcats maintained physical condition on widely varying quantities of food and that the percentage u t i l i z a t i o n of the consumed energy was r e l a t i v e l y stable. This i s probably also true for the mountain l i o n . An adult male, captured during the exploratory phase of this study i n Montana, was held i n c a p t i v i t y for seven days. His weight remained constant at 115 pounds despite the fact he refused to eat for the entire period. Data from zoos and those obtained from feeding captive animals i n this study provide an i n d i c a t i o n of the amount of meat required to keep a l i o n i n healthy condition. Adult mountain lions i n the New York Zoological Park are fed four pounds of horse meat per day, six days weekly; the cats are fasted on the seventh day (Crandall, 1964). Two mature males i n the Boise, Idaho, zoo receive d a i l y four to f i v e pounds of beef spleen treated with vitamins and minerals. Two 100-pound, 17-month-old males being raised i n semi-captivity as part of this study consumed 3.5 pounds of meat, hide and bone each per day during a 28-day feeding t r i a l . At the age of 4% months they weighed 35 pounds and consumed 1.8 pounds per day during a 15-day period. They have been fed a l l they could eat since being weaned from milk at three months of age. These feeding experiments support Schaller's speculation that t i g e r cubs require h a l f as much meat as adults. The energy output of captive lions i s undoubtedly less than that of free-65 l i v i n g a n i m a l s b u t we know t h a t w i l d i n d i v i d u a l s spend a g r e a t d e a l o f t ime i n f e e d i n g and r e s t i n g i n the immediate v i c i n i t y o f a k i l l and i n s i m p l y " l a y i n g - u p " . T h e i r e n e r g y o u t p u t i n t h e s e s i t u a t i o n s i s n o t a p p r e c i a b l y h i g h e r t h a n i n z o o s . The food r e q u i r e m e n t o f the average a d u l t : l i o n i n the Idaho P r i m i t i v e A r e a , where p r e y is;, p l e n t i f u l , i s p r o b a b l y f o u r to s i x pounds o f meat p e r d a y . A t t h i s r a t e o f c o n s u m p t i o n , a l i o n r e q u i r e s 1,460 t o 2,190 pounds o f meat p e r y e a r . Not a l l p a r t s o f l a r g e p r e y a n i m a l s a r e e d i b l e , however, and a l i o n must k i l l more i n terms o f w e i g h t than the amount a c t u a l l y e a t e n . S c h a l l e r (1967) found t h a t t i g e r s a t e 73 p e r c e n t o f a 130-pound c h i t a l b u c k . My o b s e r v a t i o n s on t h r e e a d u l t mule d e e r fed to the c a p t i v e c a t s c o r r e s p o n d to S c h a l l e r ' s f i n d i n g s - - an average o f 30 p e r c e n t was n o t e a t e n . T h i s i n c l u d e s the rumen and some v i s c e r a , b o n e s , f e e t and some h i d e , and m i s c e l l a n e o u s s c r a p s . S m a l l d e e r , however, a r e a l m o s t e n t i r e l y e a t e n , i n c l u d i n g the s p i n a l c o l u m n , s k u l l , and f e e t . T h u s , on the b a s i s o f t h e s e f i g u r e s , an a d u l t l i o n would have to k i l l about 1,898 to 2,847 pounds o f l a r g e p r e y a n i m a l s p e r y e a r . T h i s r e p r e s e n t s a minimum and assumes t h a t a l l e d i b l e p a r t s o f each c a r c a s s a r e consumed. In a r e a s where l i o n s a r e d i s t u r b e d a t the k i l l o r where s c a v e n g e r s consume s i g n i f i c a n t q u a n t i t i e s o f each c a r c a s s , more k i l l s must be made. W r i g h t (1960) found t h a t s c a v e n g e r s a t e c o n s i d e r a b l e amounts o f the k i l l s made by A f r i c a n L i o n s , and t h a t the l i o n s k i l l e d t w i c e the amount a c t u a l l y r e q u i r e d . E v i d e n c e i s overwhelming 66 that lions i n the Primitive Area do completely u t i l i z e each k i l l . Each k i l l i s buried and c l o s e l y guarded against scavengers. The only disturbing influence i n the study area has been our a c t i v i t i e s and i n some cases where a l i o n has been flushed from a k i l l i t has returned to feed. Further, as Holling (1959) points out, subsistence requirements w i l l f i x the ultimate l e v e l (of k i l l i n g ) for most predators 3 but even, those whose consumption i s less r i g i d l y deter-mined by subsistence requirements must have an upper l i m i t , even i f i t i s only determined by the time required to k i l l . One might also add to this the energy expended i n hunting and actual k i l l i n g , the risk, involved i n attacking each large prey animal, and the "economics", i n terms of the predator's welfare, of "unnecessary" k i l l i n g . On the basis of these considerations, I believe that 13898 to 23847 pounds per year represent f a i r l y accurately the actual amount k i l l e d by each adult l i o n . In determining the minimum number of large prey animals k i l l e d annually by an adult l i o n , we must consider the weight of these animals, Greer and Howe. (1964) weighed 1,127 elk k i l l e d i n winter i n Yellowstone National Park, The average of these weights and those from over 2,500 mule deer from Montana (Mackie. 1964) appear i n Table XVI. An average weight taken from the 1%-year class of both species appears a v a l i d representation of the weight of the average animal k i l l e d by l i o n s , A. greater number of young individuals are k i l l e d but these animals are almost completely eaten. Further, the greater amount of edible material obtained 67 from animals older than 1% years acts to o f f s e t this source of bias. The average weight considered, then, i s 385 pounds for elk and 140 pounds for deer. The computed number of elk required to sustain one adult l i o n per year i s 5 to 7. For deer, the number i s 14 to 20. It i s obvious that the number of elk, although s u f f i c i e n t to sustain a l i o n for a year on the basis of pounds of edible meat, is u n r e a l i s t i c . In warm weather decomposition before complete u t i l i z a t i o n would reduce the e f f i c i e n c y of use of an elk or large deer, and t h e o r e t i c a l l y would increase the k i l l . Many lesser species are available i n summer, however, and I believe this source of food acts to hold down any increase i n the k i l l of elk and deer. Table XVI Live Weights of Elk and Mule Deer* Age Elk Deer  Males Females Males Females Calves/Fawns 254 227 68 62 1% 400 370 143 135 2\ 531 471 180 143 3% 630 511 216 143 * After Greer and tfowe, 1964, and Mackie, 1964. To assess the impac,t of mountain l i o n predation on elk and deer populations, the t o t a l number of lions exerting predation, pressure on these populations must be considered. For the sake of s i m p l i c i t y , only the 1966-67 population w i l l be considered. Eight 68 a d u l t s known to be r e s i d e n t s and f o u r j u v e n i l e s dependent on r e s i d e n t females were p r e s e n t ( T a b l e V ) . C o n s i d e r i n g t h a t j u v e n i l e s r e q u i r e o n e - h a l f as much food as a d u l t s , we may s t a t e t h a t 10 a d u l t l i o n s e x e r t e d y e a r - r o u n d p r e s s u r e on the B i g C r e e k e l k adult and d e e r . Ten a d d i t i o n a l / l i o n s - - t h r e e a d u l t t r a n s i e n t s and s e v e n a d u l t s and one j u v e n i l e i n d i v i d u a l whose s t a t u s were n o t d e t e r m i n e d were known to be i n the a r e a f o r v a r y i n g l e n g t h s o f t i m e . S i x months i s a r b i t r a r i l y c h o s e n as the p e r i o d t h e s e l i o n s p r e y e d on B i g C r e e k p o p u l a t i o n s . T h e r e f o r e , 16 a d u l t l i o n s ( a w a r d i n g the one u n d e r t e r m i n e d j u v e n i l e " a d u l t " s t a t u s ) e x e r t e d p r e d a t o r y p r e s s u r e t h r o u g h o u t the y e a r . These 16 l i o n s t h e n , r e q u i r e d 30,368 t o 45,552 pounds o f l a r g e p r e y a n i m a l s p e r y e a r . In terms o f numbers,, t h i s would amount t o 90 to 112 e l k o r 224 to 320 mule d e e r . Both s p e c i e s a r e k i l l e d i n d i s c r i m i n a t e l y , a t l e a s t from the s t a n d p o i n t o f the l i o n p o p u l a t i o n as a w h o l e , b u t the r e l a t i v e r a t e s a t w h i c h e l k and d e e r a r e k i l l e d a r e n o t known. T a b l e s X I and X I I i n d i c a t e t h a t about e q u a l numbers o f e l k and d e e r a r e k i l l e d - - 4 4 e l k and 39 d e e r k i l l s were r e c o r d e d . Some b i a s , however, may be p r e s e n t i n t h e s e f i g u r e s . Some d e e r r e m a i n s , p a r t i c u l a r l y - t h o s e o f fawns and younger a n i m a l s , may go u n d e t e c t e d b e c a u s e t h e y a r e more com-p l e t e l y u t i l i z e d by the l i o n s t h e m s e l v e s and the s c a v e n g e r s w h i c h followf. B i a s was r e d u c e d by the r i g i d c r i t e r i a used to d e t e r m i n e k i l l s , b u t n o n e t h e l e s s some may e x i s t . Cowan (1947), however 3 w o r k i n g u n d e r s i m i l a r c o n d i t i o n s , a p p a r e n t l y d i d n o t b e l i e v e t h i s 69 to be of s u f f i c i e n t magnitude to warrant consideration. In his study, deer were less abundant thaii elk, yet r e l a t i v e l y more k i l l s of deer were recorded. 70 PREDATION EFFICIENCY I t i s g e n e r a l l y r e c o g n i z e d t h a t p r e d a t o r s have a low r a t e o f h u n t i n g s u c c e s s b u t , as Mech (1966) p o i n t s o u t , q u a n t i t a t i v e e v i d e n c e f o r t h i s b e l i e f i s n o t e a s i l y o b t a i n e d . Mech was a b l e to o b t a i n f i g u r e s on the s u c c e s s o f w o l f attempts to k i l l moose on I s l e R o y a l e . Of 77 moose " t e s t e d " o n l y s i x were! k i l l e d , r e s u l t i n g i n an e f f i c i e n c y r a t i n g o f 7.8 p e r c e n t . O t h e r a u t h o r s r e p o r t t h a t w o l v e s make many v a i n attempts to c a p t u r e p r e y (Cowan, 1947; M u r i e , 1944; C r i s l e r , 1956). Saunders (1963b) t r a c k e d l y n x i n snow and d e t e r m i n e d t h a t o n l y 18 o f 43 attempts to c a t c h snowshoe h a r e s were s u c c e s s f u l . S c h a l l e r (1965) s p e c u l a t e d t h a t t i g e r s made 20 to 30 u n s u c c e s s f u l attempts f o r each p r e y a n i m a l k i l l e d , and S t e v e n s o n - H a m i l t o n (1947) s t a t e s t h a t A f r i c a n l i o n f a i l u r e s t o c a p t u r e p r e y exceed the s u c c e s s e s . Rudebeck (1950, 1951) found t h r o u g h d i r e c t o b s e r v a t i o n o f E u r o p e a n r a p t o r s t h a t o n l y 7.6 p e r c e n t o f 688 attempts to s e c u r e p r e y were s u c c e s s f u l . In c o n t r a s t i s the h i g h r a t e o f s u c c e s s r e p o r t e d by P e a r s o n (1964) f o r f e r a l house c a t s p r e y i n g on M i c r o t u s , and by E s t e s and Goddard (1967) f o r A f r i c a n w i l d dogs. I t i s i m p o s s i b l e to make d i r e c t o b s e r v a t i o n s on a t t e m p t s o f m o u n t a i n l i o n s to c a p t u r e p r e y . Some a u t h e n t i c a c c o u n t s o f a c t u a l a t t a c k s on p r e y a n i m a l s have been o b s e r v e d , b u t t h e s e a r e few (Wade, 1929; Young and Goldman, 1946). N e i t h e r c a n q u a n t i t a t i v e d a t a on s u c c e s s f u l v s . u n s u c c e s s f u l attempts be g a i n e d from t r a c k i n g the a n i m a l s . T h i s i s because o f the method o f h u n t i n g employed by the l i o n . M o u n t a i n l i o n s , r a t h e r t h a n h u n t i n g an i n d i v i d u a l a n i m a l , must seek a set of conditions, a p a r t i c u l a r s i t u a t i o n i n which they are able to approach quite c l o s e l y . Once they have found these conditions and have placed themselves, through stealth, within s t r i k i n g distance, the greater percent of the actual attacks appear to be successful. It is the approach that i s c r u c i a l and more often than not i t i s d i f f i c u l t to assess the ra t i o i . of successful vs. unsuccessful approaches. In most cases one can-not determine i f a l i o n has actually made an attempt on a p a r t i c u l a r animal i f the animal escaped.' A l i o n may obviously be hunting cover and t e r r a i n where prey animals occur but i t i s impossible to judge circumstances and the lion's mistakes i n f a i l i n g to place i t s e l f within actual attacking distance. Only when a l i o n has actually launched an attack and has f a i l e d or succejeded can a r i g i d determination of success be made. If the f i n a l attack only i s considered as the "attempt" then by far the greatest percentage are successful. In 41 such instances, recorded from tracks i n snow, 34 were successful, 7 were unsuccessful. It i s obvious, however, that the "attempt" must include the all-important approach; the attack and k i l l i n g , for an experienced l i o n , appear to be the easiest part of the hunt. Mistakes and f a i l u r e s made precluding a f i n a l stalk and attack cannot be assessed, yet i t i s during this stage of the hunt that success or f a i l u r e i s determined. 72 THE MECHANICS AND FUNCTION OF MOUNTAIN LION PREDATION An assessment of predation and i t s e f f e c t on populations of prey animals must involve consideration of numerous factors. Leopold (1933) c l a s s i f i e d these factors into f i v e groups, modified here a f t e r Holling (1959): (1) density of the prey population, (2) density of the predator population, (3) c h a r a c t e r i s t i c s of the prey, e.g., reactions to predators, physical conditions, and other c h a r a c t e r i s t i c s , (4) density and quality of alternate foods available for the predator, (5) c h a r a c t e r i s t i c s of the predator. Each of these variables may exert a considerable influence and the e f f e c t of any one. may depend upon changes i n another. Information on each i s es s e n t i a l to understanding mountain l i o n predation on big-game herds, but considered separately i t t e l l s l i t t l e of the function of such predation. Only when these data are combined and analyzed w i l l they show what l i o n predation i s and how i t operates. Each of the above factors w i l l be considered with reference to findings i n this study and their i n t e r r e l a t i o n -ships interpreted. Elk and deer comprised by far the greatest percent of the winter d i e t of mountain lions i n this study; discussions w i l l be confined to these prey populations. Since Number 4 appears i n s i g n i f i c a n t i n this study, i t w i l l not be treated. Craighead's (1956) d e f i n i t i o n of the terms " a v a i l a b i l i t y " and v v u l n e r a b i l i t y " appear apt to this discussion. He uses " a v a i l -a b i l i t y " to mean that prey organisms are present, and 73 " v u l n e r a b i l i t y " to. encompassoall.' the,_physical. and b i o l o g i c a l conditions that cause one species to be preyed on more heavily than another. Density of Prey Populations It i s generally recognized that predation i s , for the most pa r t s density-dependent; e.g., predators take the species most available (McAtee, 1932; L. Tinbergen, 1946; Popham, 1942; Errington, 1936; Nicholson, 1933). Errington (1946) further recognized that the c h a r a c t e r i s t i c s of many vertebrate prey species change when the i r density exceeds the number that the available cover can support. This change causes a sudden increase i n v u l n e r a b i l i t y and, consequently, i n predation. Numbers of mule deer and elk, the p r i n c i p a l prey species i n the Big Creek area, increased on the 200 square mile study-area i n each of the three winter f i e l d seasons (Table VIII). "Effective density", as described by Haldane (1953), i s d i f f i c u l t to ascertain on an area-wide basis and does not necessarily mean density per unit atea. Deer and elk are r e s t r i c t e d to a r e l a t i v e l y small portion of the study area i n winter. Dense concentrations may occur i n some sectors of this r e s t r i c t e d wintering area, depending on snow depths and severity of weather. Numbers of deer and elk per square mile for the entire 200 square mile study area are presented here i n order to make comparisons and to establish l i o n : ungulate r a t i o s . The number of elk per square mile increased from 4 i n 1964-65 to 5.7 i n 1966-67; deer rose from 6.8 to 13 per 74 square mile during the same period. From the standpoint of r e l a t i v e abundance, i t appears that deer were more "available" than elk. The recorded k i l l s , however, do not bear this out --44 elk and 39 deer k i l l s were recorded. Cowan (1947) found that the annual di e t of wolves was not s t r i c t l y related to r e l a t i v e abundance. Deer were only one-third as abundant as elk, yet deer k i l l s were one-half as numerous as elk k i l l s . As stated previously some bias may be present i n my figures because of undetected deer k i l l s . I believe this bias, i f i t exists, i s s l i g h t ; Cowan's findings obtained i n similar t e r r a i n and under sim i l a r conditions lend strength to this contention. The nearly equal numbers of elk and deer k i l l s recorded suggest one of two things; (1) lions are selecting elk, or (2) ecologic or behavioral mechanisms are operating to make less-abundant elk more vulnerable to l i o n predation. I believe the second point i s most important -- i n t e r s p e c i f i c competition between elk and deer appears to govern to some extent v u l n e r a b i l i t y , to l i o n predation. Increasing numbers of elk have moved into the extremely rough b l u f f areas which formerly supported sizeable wintering herds of deer. Deer cannot compete with the more e f f i c i e n t browsing of elk and i n some areas have moved to higher elevations on the winter range. The b l u f f areas offe r i d e a l hunting conditions for mountain lio n s . As a r e s u l t , lions are k i l l i n g more elk than deer i n c e r t a i n sectors of the winter range. Deer, on the whole outnumber elk and t h e o r e t i c a l l y are more 75 available, yet i n s p e c i f i c areas elk are more vulnerable and a greater proportion are k i l l e d . Similar differences i n vulner-a b i l i t y of ungulates i n d i f f e r e n t types of cover and t e r r a i n have been noted by Schaller (1967) for species preyed upon by tigers and by Wright (1960) and M i t c h e l l et a l . (1965) for those subjected to l i o n predation. Density of the Mountain Lion Population The mountain l i o n population has remained stable throughout the three-year period. The density, using the figure of 16 adult lions previously computed as preying on Big Creek game populations throughout the year, i s one adult l i o n per 12.5 square miles. In 1966-67 the r a t i o of lions to deer and elk therefore was one l i o n to 163 deer and 71 elk, or one l i o n to 234 prey animals. Bourliere (1965) c i t e s lion-ungulate ratios i n African parks ranging from one l i o n per 260 to 360 prey animals. Leopold (1933) gives ratios of mountain lions to deer i n two sectors of C a l i f o r n i a of one to 200 and one to 360. If ungulate densities i n the Big Creek area are considered on a biomass basis, the l i o n : ungulate r a t i o approaches the higher r a t i o c i t e d by Leopold. The average weight considered for deer and elk was 140 pounds and 385 pounds, respectively. Therefore 71 elk, on a biomass basis, would be equivalent to 195 deer, r a i s i n g the l i o n : ungulate r a t i o to 1:358, almost exactly that of Leopold's higher figure. The density of lions has remained the same, but as shown, that of the prey species has increased. Ratios of lions to deer and e l k s 76 on a numerical basis, rose from 1:135 i n 1964-65 to 1:234 i n 1966-67. These data off e r evidence that l i o n numbers i n the Big Creek area are determined by factors other than the food supply. They further suggest that l i o n predation is not c o n t r o l l i n g ultimate numbers of these prey animals. Holling (1959) reduced the components of predation to two basic v a r i a b l e s s p r e y density and predator density. In a series of experiments with small mammal predators and pine sawfly cocoons as prey, he demonstrated two responses to changes i n prey density. The f i r s t was a change i n the number of prey consumed per predator and the second was a change i n the density of the predator. Pre-dator density, however, did not a f f e c t the consumption of prey by i n d i v i d u a l animals. Predator density i n i t i a l l y increased with prey density "ultimately ceasing to increase as some agents other than food became l i m i t i n g " . He concluded that predation can theo-retic'ally regulate the numbers of prey i f the predation is high enough to match the e f f e c t i v e reproduction by prey at "some prey density". Holling continues, "Even i f this condition does not hold, however9 o s c i l l a t i o n s of prey numbers are damped. Since the functional and numerical responses undoubtedly d i f f e r for d i f f e r e n t species of predator, predation by each i s l i k e l y to peak at a d i f f e r e n t prey density. Hence, when a large number of d i f f e r e n t species of predators are present,the declining phase of predation i s displaced to a higher prey density, so that the prey have less chance to "escape 1 the regulation exerted by predators." To evaluate 77 Holling's b e l i e f s i n respect to this more complex study we must consider prey and predator characteristics., Characteristics of the Prey Density of prey species and resultant ecologic, b i o l o g i c a l and behavioral factors are important i n predator-prey interactions. Increased density of ungulates brings about decided changes i n the environment and acts to increase v u l n e r a b i l i t y i n a number of ways. Environmental change, with respect to large hoofed species, brought about by increased density usually results i n a decrease of desirable forage plants. This decrease i n both quantity and quality of food brings about a weakened physical condition i n i n d i v i d u a l animals and the population as a whole. Animals i n poorer physical condition are likewise more vulnerable to predators. Juveniles are the f i r s t to show the effects of malnutrition and this coupled with t h e i r lack of experience i n eluding predators makes them highly vulnerable to l i o n s . Table XVII presents data on the physical condition of 32 juvenile and 40 adult elk and deer k i l l e d by mountain l i o n s . Thirteen of 19 elk over 1% years of age were i n good physical condition, but only seven of 21 calves were considered i n a good state of n u t r i t i o n a l health. The figure for good and poor adult deer are similar to those for adult elk 14 vs . 7 -- but nine of 11 fawns were i n poor condition. Assuming no s e l e c t i o n for juveniles by l i o n s , the. juveniles class shows the most decided effects of malnutrition. 78 Table XVII P h y s i c a l C o n d i t i o n of 72 Mountain Lion K i l l s : J u v e n i l e Elk and Deer Compared to Adult* Elk and Deer 1964-67 P h y s i c a l C o n d i t i o n of Adults P h y s i c a l Condition of J u v e n i l e s Year Elk Deer Elk Deer Good Poor Good Poor Good Poor Good Pobr 1964-65 3 2 4 - 2 2 2 1 1965-66 8 2 4 2 2 1966-67 2 2 6 5 5 7 1 6 TOTAL 13 6 14 7 7 14 2 9 * Adults are animals over 1-1/2 years of age. 79 Table XVIII shows the r e l a t i v e proportion of juvenile elk and deer i n the population and the incidence of these juveniles i n the recorded l i o n k i l l . It i s seen that the k i l l of juveniles greatly exceeds th e i r r e l a t i v e abundance i n the herd. It must be recognized, however, that the r e l a t i v e proportion of juveniles i n the herd more properly represents surviving juveniles rather than r e l a t i v e abundance throughout the year. No data are available on fecundity but i t obviously must exceed the figure presented. The rate at which the juveniles class f a l l s prey to lions appears to correlate to ungulate density and to weather conditions. The winter of 1964-65 was characterized by extreme snow depths and periods of prolonged cold. It must be considered a moderately "hard" winter. Calf elk and fawn deer would be expected to suffer most severely from these conditions. Overall density of these prey populations was at the lowest l e v e l i n the study period, but deer and elk herds were concentrated because of deep snow. Calves and fawns made up 50 and 38 percent, respectively, of the recorded elk and deer k i l l . In 1965r-66 weather conditions were mild. Densities of deer and elk increased on the study area as a whole but animals were not concentrated. Ratios of juvenile elk and deer to adults rose markedly (Table XVIII) but lesser numbers, on a r e l a t i v e basis, were k i l l e d by lion s . Another mild winter followed i n 1966-67, densities of elk and deer increased, and again s u r v i v a l of juveniles was better. Lion; predation on this age cl a s s , however, was the heaviest recorded. This appears to have been a re s u l t of increased Table XVIII No. of Calves § Fawns per 100 Adult Females Year Calves Fawns 1964- 65 13 23 1965- 66 27 30 1966- 67 28 34 Relative Proportion of Juvenile Elk and Deer in the Population and the Incidence of Juveniles in the Recorded Lion Kill 1964-67 Total No. Killed by Lions All Ages Elk 10 18 16 Deer 8 11 20 No. Calves § Fawns Killed by Lions 5 5 12 3 3 Percent Calves § Fawns All Animals Observed Calves Fawns Calves 9 19 20 Fawns 17 21 22.5 Percent Calves § Fawns in Total Kill Calves Fawns 50 38 28 27 75 40 TOTAL 44 39 22 14 oo o 81 v u l n e r a b i l i t y b r o u g h t about by h i g h e r d e n s i t i e s . E r r i n g t o n ' s c o n c l u s i o n s (1934) c o n c e r n i n g q u a i l d e n s i t i e s and v u l n e r a b i l i t y to p r e d a t o r s a p p l y to t h e s e d a t a . He s t a t e s , "The a b s o l u t e q u a i l d e n s i t y d i d n o t have the c l o s e c o r r e l a t i o n w i t h the r a t e o f w i n t e r p r e d a t i o n as d i d the c o m p a r a t i v e d e n s i t y . The d e n s i t y o f the p o p u l a t i o n i n r e l a t i o n to the c a r r y i n g c a p a c i t y o f the e n v i r o n m e n t , h i g h o r low, was o f fundamental s i g n i f i c a n c e . " The f o l l o w i n g p o i n t s may be made from the above d a t a : (1) s e v e r e w e a t h e r c o n d i t i o n s a r e a d e f i n i t e f a c t o r i n d e t e r m i n i n g the p h y s i c a l c o n d i t i o n o f u n g u l a t e s , and as a r e s u l t a c t to make j u v e n i l e s more s u s c e p t i b l e t o p r e d a t i o n ; (2) i n c r e a s e d d e n s i t y o f d e e r and e l k and s u b s e q u e n t o v e r b r o w s i n g o f key f o r a g e p l a n t s a c t to lower the p h y s i c a l c o n d i t i o n o f i n d i v i d u a l a n i m a l s and the p o p u l a t i o n as a w h o l e . T h i s o c c u r s i n the absence o f s e v e r e weather and a g a i n j u v e n i l e s a r e most s e r i o u s l y a f f e c t e d . These d a t a c o u p l e d w i t h i n f o r m a t i o n on. e f f e c t i v e r e p r o d u c t i o n and a d i r e c t a p p r a i s a l o f range c o n d i t i o n s shed a d d i t i o n a l l i g h t on l i o n - u n g u l a t e i n t e r - r e l a t i o n s h i p s . Cowan (1950) s t a t e s t h a t m a l n u t r i t i o n was the most i m p o r t a n t f a c t o r i n s u r v i v a l o f j u v e n i l e e l k and d e e r on o v e r s t o c k e d ranges i n C a n a d i a n p a r k s . He found t h a t p r e g n a n c i e s i n e l k , e x p r e s s e d as a p e r c e n t a g e o f a d u l t cows, were 63 p e r c e n t , b u t t h a t l i v e c a l v e s i n mid-summer were o n l y 50 p e r c e n t , and by the f o l l o w i n g s p r i n g o n l y 21 p e r c e n t remained a l i v e . The heavy l o s s o f c a l v e s was a t t r i b u t e d a l m o s t e x c l u s i v e l y to m a l -n u t r i t i o n . The r a t i o s o f j u v e n i l e e l k and d e e r t o a d u l t females 82 on t h e s e o v e r s t o c k e d ranges (Cowan, 1947, 1950) a p p r o x i m a t e f a i r l y c l o s e l y the r a t i o s o b t a i n e d i n t h i s s t u d y . F o r the p e r i o d 1943 t o 1945, Cowan found 20, 21, and 15 e l k c a l v e s p e r 100 a d u l t cows s u r v i v i n g t h e i r f i r s t y e a r o f l i f e . In t h i s s t u d y , the f i g u r e s f o r the y e a r s 1964 to 1967 were 13, 27, and 28 r e s p e c t i v e l y . Cowan (1950) found 26 and 15 mule d e e r fawns p e r 100 a d u l t does i n the s p r i n g ; r a t i o s i n t h i s s t u d y were 23, 3 0 , and 34. Cowan's c l a s s i f i c a t i o n c o u n t s were made i n s p r i n g , mine a r e a g g r e g a t e c o u n t s made t h r o u g h o u t the w i n t e r . The g r e a t e r p r o p o r t i o n o f a n i m a l s were c l a s s i f i e d i n l a t e w i n t e r and s p r i n g , however, when a n i m a l s were more c o n c e n t r a t e d ; t h i s may e x p l a i n the somewhat h i g h e r f i g u r e s o b t a i n e d i n my work. F u r t h e r , two m i l d w i n t e r s i n 1965-66 and 1966-67 have been c o n d u c i v e to g r e a t e r j u v e n i l e s u r v i v a l . The f a c t r e m a i n s , however, t h a t e f f e c t i v e r e p r o d u c t i o n - -s u r v i v a l o f j u v e n i l e s t o y e a r l i n g age - - i s n o t h i g h . R o b i n e t t e and O l s e n (1944) found s u r v i v a l o f 58.5 p e r c e n t i n mule d e e r on a p r o d u c t i v e range i n U t a h , a n d K. G r e e r ( p e r s . comm.) r e p o r t s somewhat s i m i l a r f i g u r e s f o r e l k a f t e r d r a s t i c r e d u c t i o n o f the Y e l l o w s t o n e h e r d . The r o l e o f m o u n t a i n l i o n ' p r e d a t i o n i n t h e s u r v i v a l o f the j u v e n i l e c l a s s i s n o t known w i t h c e r t a i n t y , b u t d a t a from o t h e r s t u d i e s s u g g e s t i t s i n f l u e n c e may be o f a m i n o r n a t u r e . L i o n s k i l l a f a r g r e a t e r p r o p o r t i o n o f t h e s e a n i m a l s b u t the e f f e c t o f t h i s k i l l i n g on u l t i m a t e numbers may n o t be so i m p o r t a n t as i t a p p e a r s . Cowan (1947) a t t r i b u t e d j u v e n i l e e l k l o s s e s a l m o s t w h o l l y t o 83 malnutrition. Further, he compared wolf-inhabited and wolf-free ranges and found that s u r v i v a l of juvenile elk and deer was v i r -t u a l l y i d e n t i c a l . Here again the c r i t i c a l l i m i t i n g factor was range conditions. K l e i n and Olson (1960) reported on wolf-inhabited and wolf-free islands and the status of deer populations on these islands. Where wolves were absent, deer populations were stable or slowly increasing i n excess of the winter range capacity, they suffered heavy winter mortality, and winter ranges were severely deteriorated. Where wolves occurred, t y p i c a l c h a r a c t e r i s t i c s of deer herds were rapidl y increasing populations, l i g h t winter • mortality from starvation, and winter ranges i n f a i r to good condition. They concluded that wolf predation was not the l i m i t i n g factor. Lack (1954) c i t e s Schuz and K l u i j v e r , working with the white stork and great t i t , respectively, as finding no c o r r e l a t i o n between reproductive success and the l e v e l of the breeding popu-l a t i o n i n the subsequent year. The work of Tompa (1963) with song sparrows and Jenkins (1963) with red grouse lend support to this conclusion. Further, Hoffmann (1958) found no c o r r e l a t i o n between reproductive success and subsequent breeding densities i n voles. Lack (1954) concluded there i s no such relationship and that numbers are controlled p r i n c i p a l l y by variations i n the death rate of juve-n i l e s between f a l l and spring. The point made here i s that population levels seek a "norm" compatible with the multitude of factors making up the environment, including a l l of the depressing 84 mechanisms operating. Errington (1956), discussing muskrat populations, disclosed his ideas concerning depressive influences: P a r t i c u l a r l y worth emphasizing i n appraisals of net population effects of agencies, of mortality i s the evidence of the broad categories of muskrats most l i k e l y to be preyed upon by predatory vertebrates -- excluding man --have poor l i f e expectancies, anyway. They are the l i k e l i e s t candidates for elimination through one agency or another, whether the minks are abundant, scarce, or absent or whether the other common muskrat predators are abundant, scarce, or absent. In the f r i t t e r i n g away of doomed surpluses, or of parts of populations doomed because of emergencies, i t seems to make so l i t t l e difference i n the end what the s p e c i f i c agencies of mortality may be that I rarely f e e l sure of the l o g i c a l propriety of ascribing true depressive influence to any one agency. Of what demonstrable population significance i s any agency of mortality as long as much the same patterns i n population trends continue to show up, seemingly i r r e s p e c t i v e of whether that agency operates or not? Craighead and Craighead (1956) took exception to Errington's view, stat i n g that i t i s not the fact that animals die that i s important, but how they die and the resultant influence on the survivors. This point w i l l be discussed l a t e r . An appraisal of range conditions i n the Big Creek area confirmed the b e l i e f that these ranges are overstocked. The major browse forage species are c u r l l e a f mountain mahogany and bitterbrush. Certain bunchgrasses are important for elk but often these are buried under crusted snow and are unavailable. One hundred browse plants were sampled i n the spring of 1966-67 i n each of six key areas. Mr. Jack E. Schmautz, Range Conservationist, D i v i s i o n of Range and W i l d l i f e Management, U. S. Forest Service, kindly agreed 85 to review my data and comment on range conditions. The following excerpts from Mr. Schmautz1s appraisal are quoted with his permission: The six areas you sampled are c e r t a i n l y i n unsatis-factory condition as far as game ranges are concerned. Moreover, the trends are s t i l l downward. Use was excessive l a s t winter and has, undoubtedly, been so for a number of years. It i s evident the forage production p o t e n t i a l i s far from being attained. The high percentage of plants i n form classes 3 and 6 and the large number i n form classes 7 and 8 indicate the poor condition of the range. Seventy-six to one hundred percent of the l i v e palatable shrubs available to game have been heavily clubbed. Almost 30 percent of the desirable shrubs are producing no available forage at a l l because they are either dead or grown completely out of reach. Furthermore, the mahogany, at least, i s not regenerating. Such range conditions are quite c h a r a c t e r i s t i c of big game areas where game herds are underharvested. It i s fortunate that the two major palatable species present, mountain mahogany and bitterbrush, are long-l i v e d species, and can withstand long periods of over-use; p a r t i c u l a r l y mahogany, can grow out of reach of the animals. These plants provide the seed for regeneration and establishment of new stands during years of low game populations. As stated previously, the wintjers of 1965-66 and 1966-67 must be considered mild i n the study area because of lack of snow i n low elevations and the absence of prolonged low temperatures. In spite of this and the fact that other forage species were available, game animal use on the key species was excessive. This indicates an over-abundance of game animals wintering i n the Big Creek area. It further suggests cause's for the low sur v i v a l rate of juvenile elk and deer. 86 Comparison of the physical condition of animals k i l l e d by mountain lions to those shot i n a randomly col l e c t e d sample offers further insight into the function of l i o n predation. T h i r t y - s i x of 72, or 50 percent of the elk and deer k i l l e d by lions were i n poor physical condition. In a randomly collected sample i n 1966-67 (Table IX), f i v e of 14, or 36 percent were i n poor condition. The collected sample i s inadequate, but the greater proportion of less f i t animals i n the recorded l i o n k i l l may indicate that lions are taking r e l a t i v e l y more poor animals. It appears that lions are k i l l i n g those animals most vulnerable and this v u l n e r a b i l i t y i s determined by d i f f e r e n t physical, b i o l o g i c a l , and ecologic factors. Characteristics of the Predator The mountain lion's mode of hunting i s a factor i n deter-mining the kind of prey animal k i l l e d . Unlike the canids who r e l y on speed to overtake th e i r prey, the l i o n must place i t s e l f , through stealt h , very close before i t launches an attack. This hunting technique c l e a r l y could r e s u l t i n the k i l l i n g of animals e n t i r e l y d i f f e r e n t i n a number of respects from those k i l l e d by predators employing an open-type attack. One would expect weakened and sick animals to f a l l prey more re a d i l y when chased long distances by wolves. Young and very old animals often make up the bulk of the k i l l of these types of predators (Murie, 1944; C r i s l e r , 1956; Mech, 1966; Cowan, 1947). The technique employed by l i o n s , however, makes no such cl e a r d i s t i n c t i o n -- with few exceptions, any animal 87 placing i t s e l f i n a vulnerable p o s i t i o n i n the environment i s subject to l i o n predation. The kind of animal k i l l e d by. lions is' more l i k e l y determined by factors other than the mode of hunting u t i l i z e d by the l i o n . We have seen that these include physical, b i o l o g i c a l , and ecologic considerations together or separately acting to increase the v u l n e r a b i l i t y of c e r t a i n classes of individuals i n the prey population. That the kind of animal k i l l e d by lions i n this study, with respect to age, physical condition, and behavioral c h a r a c t e r i s t i c s , i s not unlike that k i l l e d by "chasing" predators preying on similar overstocked populations may not be coincidental. Vulnerable animals -- Errington's "surpluses" -- appear doomed, no matter what agent k i l l s them (Errington, 1956), be i t starvation, accidents, or predation by "stealthy" or "chasing" predators. At f i r s t glance i t would appear that mountain lions were se l e c t i v e i n t h e i r hunting and k i l l i n g . The high incidence of juveniles i n the k i l l quite above that of their r e l a t i v e abundance suggests that these; young animals are sought out. I believe, however, that while some s e l e c t i v i t y for juvenile elk may be practiced by a few in d i v i d u a l s , v u l n e r a b i l i t y brought about by the previously discussed factors i s much more important. Evidence supporting this b e l i e f has already been presented and discus:s,ed. Equal numbers of adult deer of both sexes-were k i l l e d . When we consider the r e l a t i v e abundance of adult bucks and does (Tables VI and XIII) we see that r e l a t i v e l y more bucks than does f a l l prey 88 to l i o n s , Bucks tend to be more s o l i t a r y than does and frequent rougher t e r r a i n ; this may increase their v u l n e r a b i l i t y . The same i s true of mature b u l l elk, but i t appears they are r e l a t i v e l y immune to attack. Only f i v e b u l l s 2% years and older were recorded i n the k i l l ; two of these were 2\ year-olds and could not be considered "prime". A l l were k i l l e d by mature male lion s . A s t r i k i n g example of this "negative s e l e c t i v i t y " was recorded by tracking Number 3, a 151 pound male l i o n . This l i o n stacked three six-point b u l l s u n t i l he was apparently within attacking distance. He then retreated, c i r c l e d the three b u l l s , stalked and k i l l e d a yearling b u l l within 150 yards of the others. The size of mature bu l l s may be the major deterrent but i t i s also possible that lions fear t h e i r antlers. Some cows reach the size of younger prime b u l l s , yet cows appear to be taken indiscrimately. Lions must attack the head region of elk to k i l l them e f f e c t i v e l y , and the heavy antlers may be recognized as formidable weapons. Other workers have recognized the reluctance of predators to attack larger, more dangerous prey animals, Schaller (1967) found tigers attacking adult gaur infrequently, though the juveniles were taken; fr e e l y , M i t c h e l l et. a_l. (1965) believes that r e l a t i v e size is the main factor determining the p o s s i b i l i t y of A f r i c a n lions k i l l i n g any p a r t i c u l a r animal, and Stevenson - Hamilton (1947) recognized the security from lions of dangerous animals such as sable and roan, W61ves on Isle Royale "tested" but r a r e l y k i l l e d prime moose (Mech, 1966) and Estes and Goddard (1967) found wild 89 dogs i n A f r i c a h i g h l y s e l e c t i v e f o r s m a l l e r p r e y s p e c i e s . B o u r l i e r e (1963) s t a t e s t h a t " C a r n i v o r e s a c t u a l l y o n l y p r e y upon h e r b i v o r e s o f about the same s i z e and w e i g h t o " T h i s g e n e r a l i z a t i o n i s c l e a r l y open to d i s p u t e b u t i t does emphasize the f a c t t h a t r e l a ^ t i v e p r e y s i z e i s a f a c t o r i n p r e d a t o r - p r e y r e l a t i o n s h i p s (see R o s e n z w e i g , 1966). I c o n s i d e r i t s i m p o r t a n c e i n the d e t e r m i n a t i o n o f e l k numbers o f a s e c o n d a r y n a t u r e . P r e v i o u s l y c i t e d sex r a t i o s and p o p u l a t i o n c h a r a c t e r i s t i c s f o r e l k r e p o r t e d by Cowan (1947) f o r w o l f - h u n t e d and w o l f - f r e e p o p u l a t i o n s s u p p o r t t h i s b e l i e f . Data o b t a i n e d i n t h i s s t u d y o f f e r e v i d e n c e t h a t p r e d a t i o n by m o u n t a i n l i o n s i s i n e f f e c t i v e i n c o n t r o l l i n g u l t i m a t e numbers o f e i t h e r d e e r o r e l k . H o l l i n g (1959) has p o i n t e d out the d i f f e r e n c e between " c o n t r o l " , w h i c h c a n be e x e r c i s e d by a d e n s i t y - i n d e p e n d e n t f a c t o r s u c h as; w e a t h e r , and " r e g u l a t i o n " , w h i c h c a n o n l y r e s u l t from an i n t e r a c t i o n w i t h a d e n s i t y - d e p e n d e n t f a c t o r . He showed t h a t p r e d a t i o n o v e r some ranges o f p r e y d e n s i t y e x h i b i t e d a d i r e c t d e n s i t y - d e p e n d e n t a c t i o n (see Popham, 1942) and s t a t e d t h a t , " T h i s i s a l l t h a t i s r e q u i r e d f o r a f a c t o r to r e g u l a t e " . We have s e e n t h a t d e n s i t y d i d a f f e c t v u l n e r a b i l i t y o f d e e r and e l k i n t h i s s t u d y and t h a t l i o n p r e d a t i o n d i d r e s p o n d to d e n s i t y change. To r e g u l a t e , however, p r e d a t i o n r a t e must e q u a l the e f f e c t i v e b i r t h - r a t e ( H o l l i n g , 1959). C l e a r l y t h i s p r e d a t i o n r a t e was n o t a c h i e v e d by l i o n s on e l k and d e e r p o p u l a t i o n s i n t h i s s t u d y . W h i l e l i o n p r e d a t i o n appears i n e f f e c t i v e i n l i m i t i n g u n g u l a t e p o p u l a t i o n s , the^ damping o f o s c i l l a t i o n s o f t h e s e 90 populations can be important. Removal of 200 to 400 prey animals per year on the study area i s a s i g n i f i c a n t factor i n damping v i o l e n t fluctuations of numbers. Predation's damping e f f e c t has been recognized by numerous other workers (Craighead, 1956; P i t e l k a , et a l . , 1955; Holling, 1959). Indeed, Klomp (1956) considers the damping of o s c i l l a t i o n s of animal numbers to be as important as regulation. The damping and protraction of ungulate population fluctuations can only have a b e n e f i c i a l e f f e c t on the environment. Damping can act to reduce range damage and serious overstocking may be averted u n t i l such time as other l i m i t i n g forces may come into operation. The " e f f e c t " of l i o n predation i s not limited to damping prey o s c i l l a t i o n s . The e f f e c t and influence of this predation on surviving animals are extremely important. Hibben (1939) reported that 11 l i o n - k i l l e d deer he examined a l l exhibited "malproportion of body and limb". He recognized the inadequacy of this sample but f e l t that this might be a natural means for conforming a species to a norm. A l l e n (1954), quoting Thompson, stressed the role of the l i o n i n the evolu.tion of deer, and Lagler (1941) f e l t that "gaminess" of such a f i s h as the smallmouth bass i s due to the s u r v i v a l , over many centuries, of those best f i t t e d to escape their enemies. Buechner (1960) concluded that predator pressure shaped the evolution of mountain sheep, and Klopfer (1962) stressed the r o l e of predation i n the evolution of insects and birds. 91 F i e l d and e x p e r i m e n t a l d a t a s u p p o r t t h i s t h e o r y , Popham (1942) has shown e x p e r i m e n t a l l y t h a t the s e l e c t i v e a c t i o n o f p r e d a t o r s tends t o remove p r e y i n d i v i d u a l s p o s s e s s i n g h a r m f u l a d a p t i v e c h a r a c t e r s . These i n d i v i d u a l s may p o s s e s s n o n - a d a p t i v e p h y s i c a l o r b e h a v i o r a l c h a r a c t e r i s t i c s , o r t h e y may be "dumb", c o r r e s p o n d i n g t o L e o p o l d ' s (1933) " s u c k e r l i s t " . In any e v e n t , Popham's work s u g g e s t s t h a t p r e d a t i o n removes t h e s e a n i m a l s from the b r e e d i n g p o p u l a t i o n , p r e v e n t i n g the s p r e a d o f u n d e s i r a b l e t r a i t s . T h e r e i s no q u e s t i o n t h a t i n d i v i d u a l s p o s s e s s i n g u n d e -s i r a b l e b e h a v i o r a l o r p h y s i c a l c h a r a c t e r s a r e more v u l n e r a b l e t o m o u n t a i n l i o n s ; t h e s e a n i m a l s a r e " c u l l e d " from the h e r d by l i o n p r e d a t i o n . The r e c e n t work o f F o r d (1964) and K e t t l e w e l l (1956) w i t h moths s e l e c t i v e l y p r e y e d upon by b i r d s i n E n g l a n d l e n d s s t r e n g t h t o t h e i d e a t h a t p r e d a t i o n i s a s t r o n g e v o l u t i o n a r y f o r c e . M o u n t a i n l i o n s p r e v e n t " y a r d i n g " by d e e r and e l k and t h i s a l o n e i s p e r h a p s more i m p o r t a n t i n an e c o l o g i c sense t h a n the a c t u a l r e m o v a l o f a n i m a l s . The mere p r e s e n c e o f a l i o n o r f a m i l y o f l i o n s i n a l o c a l a r e a o r d r a i n a g e does n o t appear t o a l a r m game a n i m a l s . When a k i l l i s made, however, the r e a c t i o n i s s t r i k i n g . Deer and e l k i m m e d i a t e l y l e a v e the a r e a , c r o s s i n g t o the f a r s i d e o f a d r a i n a g e and i n some c a s e s l e a v i n g t o e n t e r a d i f f e r e n t d r a i n a g e . T h i s b e h a v i o r , o b s e r v e d w i t h o u t e x c e p t i o n , a c t s t o d i s t r i b u t e game a n i m a l s . I t s i m p o r t a n c e on r e s t r i c t e d , o v e r u s e d range i s o b v i o u s . L e o p o l d (1933) f e l t t h a t h a r a s s m e n t by p r e d a t o r s has an a d v e r s e e f f e c t on p r e y a n i m a l s , b u t he went on t o 92 point out that animals l i v i n g within the carrying capacity of thei r range suffer l i t t l e from such harassment. He further recognized the b e n e f i c i a l effects of predator disturbance i n the d i s t r i b u t i o n of prey species, c i t i n g deer on Vancouver Island as an example of prey reaction to release from predatory pressure. Deer congregated on a small segment of their o r i g i n a l range and severly overgrazed i t when wolves and lions were k i l l e d o ff. Cartwright (1944) found spacing of nesting i n r e l a t i o n to time among Hungarian partridge i n western Canada. Predators repeatedly destroyed high proportions of the nests, forcing renesting and thus insuring that unfavorable weather would not eliminate an entire hatch. Marston (1942) reported that bobcats hunting i n deer "yards" i n Maine kept deer a l e r t and i n some cases drove them from congested areas. From the foregoing we see that predation can have a profound e f f e c t on prey populations. Predation may or may not regulate those populations but i t s influence, aside from actual k i l l i n g , has important and far-reaching e f f e c t s . These effects may be equally important as actual regulation. Quoting Craighead and Craighead (1956): " I t would appear that on any area of land, animal populations tend toward s t a b i l i t y of inter r e l a t i o n s h i p s and that predation i n 'greater or less degree plays an important role i n establishing and maintaining such a state of balance." 93 The. Function of Mountain Lion Predation: Conclusions In the preceding sections, the following points have been established: (1) Populations of deer and elk, the principal prey species, increased during the three year period. This increase occurred in spite of both lion and human predation. (2) The lion population remained stable. These data indicate that lion predation was not limiting these ungulate populations. They show further that lion numbers were limited by factors other than the food supply. Limiting factor is used here as the factor that outweigh^ a l l the others in the extent to which i t reduces the increase rate. Winter food appeared to be the most important factor limiting elk and deer populations. Weather determined to some extent the availability of certain forage plants and "thus indirectly acted as a limiting factor. Intraspecific relationships, manifested through t e r r i t o r i a l i t y , acted to limit lion numbers. From the standpoint of determining ultimate numbers of elk and deer, free from the limitation of time3 we may conclude that lion predation was inconsequential. The function of lion predation, however, is a more complex phenomenon than that shown on a purely numerical basis. The removal of animals by a population of lions acts to lower the rate of prey increase before more drastic forces, such as disease, or starvation,, become dominant. Thus lion, predation dampens and protracts severe prey oscillations. The kind of animal removed is important,, and 94 has b e e n shown t o be a f u n c t i o n o f d i f f e r e n t f a c t o r s a c t i n g s e p a r a t e l y o r c o l l e c t i v e l y to i n c r e a s e v u l n e r a b i l i t y . These i n c l u d e p r e y d e n s i t y , b e h a v i o r , age, h e a l t h , i n t e r - and perhaps i n t r a -s p e c i f i c s t r i f e , and the l i o n ' s p r e d a t o r y c h a r a c t e r i s t i c s . No e v i d e n c e was found f o r d i r e c t s e l e c t i o n by l i o n s , e x c e p t a g a i n s t a d u l t b u l l e l k . In t h i s s t u d y , where p r e y p o p u l a t i o n s were o v e r -a b u n d a n t , l i o n s k i l l e d a greate 'r p r o p o r t i o n o f v e r y young and v e r y o l d a n i m a l s and the g r e a t e r p e r c e n t a g e were i n p o o r c o n d i t i o n . T h i s p a t t e r n o f p r e d a t i o n appears u n i v e r s a l where p r e y p o p u l a t i o n s exceed the c a r r y i n g c a p a c i t y (Cowan, 1947; M u r i e , 1944; E r r i n g t o n , 1946), r e g a r d l e s s o f the type o f p r e d a t o r o p e r a t i n g . I t a l s o appears t h a t p r e d a t o r p o p u l a t i o n s p r e y i n g on o v e r - a b u n d a n t p r e y p o p u l a t i o n s a r e s e l f - l i m i t e d . Where p r e y s p e c i e s o c c u r w i t h i n the c a r r y i n g c a p a c i t y o f the e n v i r o n m e n t , a d i f f e r e n t p r e d a t i o n p a t t e r n , w i t h r e g a r d t o the k i n d o f p r e y a n i m a l k i l l e d , m i g h t be e x p e c t e d 3 i . e . , more p r i m e a n i m a l s a r e k i l l e d ( W r i g h t , 1960; M i t c h e l l , e t a l . , 1965; S c h a l l e r , 1967), Under t h e s e c o n d i t i o n s , however, the p r e d a t o r p o p u l a t i o n may be l i m i t e d by the food s u p p l y ; W r i g h t (1960) found t h i s t o be the c a s e i n A f r i c a , In an e c o l o g i c a l s e n s e , the i n f l u e n c e o f l i o n p r e d a t i o n on s u r v i v i n g p r e y a n i m a l s may be more i m p o r t a n t t h a n the a c t u a l k i l l i n g o f a n i m a l s . L i o n s have been shown to f o r c e the d i s t r i b u t i o n o f e l k and d e e r o n . l i m i t e d w i n t e r r a n g e . T h i s i s d o u b l y i m p o r t a n t t o u n g u l a t e s p e c i e s e x h i b i t i n g weak o r n o n - t e r r i t o r i a l b e h a v i o r 95 which allows them to over/populate an area and seriously damage the habitat. M i t c h e l l et a_l. (1965) has recognized the importance of predation on such n o n - t e r r i t o r i a l species i n A f r i c a , and Errington (1956) stated "The less that strong t e r r i t o r i a l i t y or other s e l f -l i m i t a t i o n enters population equations s the moire something else must do the l i m i t i n g . " Lion predation appears incapable of l i m i t i n g elk and deer populations in; the Idaho Primitive Area s but the e f f e c t and influence of such predation i s of great significance i n maintaining;, or i n seeking to maintain,, ecologic s t a b i l i t y i n a wilderness environment. SUMMARY 96 This study was designed to (1) investigate the dynamics of a mountain l i o n population, and (2) to assess the impact of a population of lions on populations of big game animals„ The research was c a r r i e d on i n the Idaho Primitive Area; intensive work was limited to the winter and early spring seasons, Lionjj' population numbers were stable during the three-year study period 3 and available evidence indicates the present population l e v e l existed for some time p r i o r to the s t a r t of the study. I n t r a s p e c i f i c relationships, manifested through t e r r i t o r i a -l i t y 9 acted to l i m i t l i o n numbers and maintain population s t a b i l i t y . Dispersal and mortality, p a r t i c u l a r l y of young i n d i v i d u a l s s appeared to be important l i m i t i n g mechanisms. The population was centered around a nucleus of mature individuals well-established on t e r r i t o r i e s 9 but segments of the population were dynamic s exhibiting an inflow and outflow of individuals from season to season. These transients were composed predominantly of young animals. S t r i f e appeared to be kept to a minimum by a "mutual avoid= ance" behavioral mechanism. Specific hunting t e r r i t o r i e s were shared but appeared never to be used by more than one l i o n or family of lions at a time. Individuals, regardless of sex 5 appeared to respect the presence of another i n a s p e c i f i c area. The "mutual avpidance" hypothesis i s advanced as an important factor i n the maintenance of l i o n populations. This mechanism provides for the 97 d i s t r i b u t i o n of lions i n both space and time without c o s t l y fighting. It also appears to insure greater success i n securing large prey animals, Population size of prey species mule deer, elk, and bighorn sheep --was established by making ground and a e r i a l counts each year. Bighorn sheep numbers remained constant during the three-year period, but populations of deer and elk, the p r i n c i p a l prey species, increased. Analysis of six key winter range areas indicated that key browse species, the only food available to ungulates during periods of inclement winter weather, were severely over-grazed. This excessive use occurred i n spite of two successive mild winters when other forage plants were available. The range was considered overstocked by deer and elk. Forty-four elk and 39 deer were recorded as d e f i n i t e l y k i l l e d by lions during the three-year period. Only two k i l l s of bighorn sheep were found; l i o n predation on this species appeared i n s i g -n i f i c a n t . Seventy-five percent of the elk k i l l e d by lions were 1% years old or less and 9% years or older; 57 percent of the deer k i l l s were i n these age classes. More "young" than "old" animals were k i l l e d . F i f t y percent of a l l the elk and deer k i l l e d were considered i n poor condition. Five of 14 deer and elk, or t h i r t y - s i x percent of a randomly co l l e c t e d sample shot i n 1966-67 were i n poor condition. It was concluded that lions were non-selective i n their k i l l i n g , 98 except for "negative selectivity" in the case of mature bull elk 9 and that vulnerability of certain classes of prey ungulates were determined by different factors. These factors, acting , separately or collectively to increase vulnerability, included prey density, behavior, age, health, inter- and perhaps intraspecific s t r i f e , and the lion's predatory characteristics. It was concluded that elk and de^r populations were limited by the winter food supply and that predation by lions was incon-sequential in determining ultimate .numbers of elk and deer. Lion predation, however, is a powerful force acting to dampen and protract severe prey oscillations, and to distribute ungulates on restricted, c r i t i c a l range. From the theoretical standpoint, i t also appears to be a strong evolutionary force, acting to remove less f i t individuals from the population. The effects and influence of such predation are considered of great significance in the maintenance of ecologic s t a b i l i t y in wilderness environments. 99 LITERATURE CITED Allen, Durward L. 1954, Our w i l d l i f e legacy. Funk and Wagnalls Co. , New York, 4.22 pp. Bischoff, Arthur I. 1954. Limitations of the bone marrow technique i n determining malnutrition i n deer. Proc. W. Assn. Game and Fish Comm. 34:205-210. 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E f f e c t i v e n e s s i n n a t u r e o f the s o - c a l l e d a d a p t a t i o n s i n the a n i m a l kingdom, c h i e f l y as i l l u s t r a t e d by the food h a b i t s o f N e a r c t i c b i r d s . S m i t h s o n i a n M i s c . C o l l . 8 5 : 1 - 2 0 1 . M c D o u g a l l s W. Bo, and H. A. B a g g l e y . 1956. P l a n t s o f Y e l l o w s t o n e N a t i o n a l P a r k . Y e l l o w s t o n e L i b r a r y and Museum A s s o c . 186 p p . M a c k i e , R i c h a r d J . 1964. Montana d e e r w e i g h t s . Mont. W i l d l . , W i n t e r 1964. Mars t o n 9 M. A . 1942. W i n t e r r e l a t i o n s o f b o b c a t s to w h i t e - t a i l e d d e e r i n M a i n e . J . W i l d l . Mgmt. 6 : 3 2 8 - 3 3 7 . Mech, L . D a v i d . 1966. The w o l v e s o f I s l e R o y a l e . Fauna o f N a t . P a r k s o f the U. S. Fauna S e r i e s 7. 21Q;pp. 104 M i t c h e l l , Bo Lo, J. B. Shenton, and J. C. M. Uys. 1965, Predation on large mammals i n the Kafue National Park, Zambia, Zool, Africana 1:297-318. Mohr, C. 0. 1947. Table of equivalent populations of North American small mammals. Am. Mid. Nat. 37:223-249. Murie^ A. 1944. The wolves of Mount McKinley. Fauna of Nat. Parks of the U. S. Fauna Ser. No. 5:238 pp. Nicholson, A. J. 1933. The balance of animal populations. J. An. Ecol. 2:132-178. Pearson, Oliver P. 1964. Carnivore-mouse predation: an example of i t s i n t e n s i t y and bioenergetics „ J. Mammal. 45': 177-188. Peterson, C. G. J. 1896. The yearly immigration of young p l a i c e into the Limf jord from the German Sea. Dept. Danish B i o l . Sta for 1895, 6:1-77. P i t e l k a , Frank A., P. Q. Tomich, and G. W. Tr e i c k e l . 1955. Ecological relations of jaegers and owls as lemming predators near Barrow, Alaska. Ecol. Mono. 25:85-117. Popham, E. J. 1942. Further experimental studies of the selec t i v e action of predators. Proc. Zool. Soc. Lond., Ser. A-112:105-117. Qup-mby, D. C , and J. E. Gaab. 1.937° Mandibular d e n t i t i o n as an age indicator i n Rocky Mountain elk. J. Wildl. Mgmt. 21:435-451. Rausch, Robert. 1950. Observations on histopathological changes associated with starvation i n Wisconsin deer. J. Wildl. Mgmt. 14:156-161. Robinette, W. L., and 0. A„ Olspn. 1944. Studies of the productivity of mule deer i n cen t r a l Utah. Trans. N. Am. Wild. Conf. 9:156-161. G, Rogers, and J. S„ Gashwiler. 1957. Notes on tooth development and wear for Rocky Mountain mule deer. J. Wild l . Mgmt. 21:134-153. c S J. S. Gashwiler, and 0. W. Morris. 1959. Food habits of the cougar i n Utah and Nevada. J. Wildl. Mgmt. 23:261-273. 105 . 1961. Notes on c o u g a r p r o d u c t i v i t y and l i f e h i s t o r y . J . Mammal. 4 2 : 2 0 4 - 2 1 7 . R o s e n z w e i g , M i c h a e l L . 1966. Community s t r u c t u r e i n s y m p a t r i c c a r n i v o r a . J . Mammal. 4 7 : 6 0 2 - 6 1 2 . Rudebeck, G. 1950. The c h o i c e o f p r e y and modes o f h u n t i n g o f p r e d a t o r y b i r d s w i t h s p e c i a l r e f e r e n c e t o t h e i r s e l e c t i v e e f f e c t . O i k o s 2:65-88 . 1951. ( c o n t . ) O i k o s 3 : 2 0 0 - 2 3 1 . S a u n d e r s 9 J a c k K. , J r . 1963a. Movements and a c t i v i t i e s o f the; l y n x i n Newfoundland. J . W i l d l . Mgmt. 2 7 : 3 9 0 - 4 0 0 . . 1963b. Food h a b i t s o f the l y n x i n Newfoundland. J . W i l d l . Mgmt. 2 7 : 3 8 4 - 3 9 0 . S c h a l l e r , George B . , 1965. My y e a r w i t h the t i g e r s . L i f e 5 8 : 6 0 - 6 6 . . 1967. The d e e r and the t i g e r . U n i v . o f C h i c a g o P r e s s , C h i c a g o . 370 p p . S c h n a b e l , Z . E . 1938. E s t i m a t i o n o f the t o t a l f i s h p o p u l a t i o n o f a l a k e . Am. Math. M o n t h l y 4 5 : 3 4 8 - 3 5 2 . Shenon, P h i l i p J . and John C. Reed. 1936. Down I d a h o ' s r i v e r o f no r e t u r n . N a t . Geog. M a g . , 7 0 : 9 4 - 1 3 6 . S m i t h 9 Dwight R. 1954. The b i g h o r n sheep i n Idaho; i t s s t a t u s , l i f e h i s t o r y , and management. Idaho W i l d l i f e B u l l . No. 1, 154 p p . S o u t h w i c k , C. H. 1962. P a t t e r n s o f i n t e r g r o u p s o c i a l b e h a v i o r i n p r i m a t e s , w i t h s p e c i a l r e f e r e n c e to r h e s u s and h o w l i n g monkeys. Ann. N. Y. A c a d . S c i . , 102:436-454. S t e n l u n d , M. H . 1955. A f i e l d s t u d y o f the t i m b e r w o l f ( C a n i s l u p i s ) on the S u p e r i o r N a t i o n a l F o r e s t , M i n n e s o t a . M i n n . D e p t . C o n s . T e c h . B u l l . 4 , 55 p p . S t e v e n s o n - H a m i l t o n , J . 1947. W i l d l i f e i n South A f r i c a . C a s s e l l and C o . s L t d , London. 364 p p , T i n b e r g e n , L„ 1946. De sperwer a l s r o o f v i j a n d v a n z a n g v o g e l s . A r d e a 34. Reviewed by P. H . T. H a r t l e y , E c o l , 2 8 : 3 2 6 - 3 2 8 , T i n b e r g e n , N. 1957. F u n c t i o n s o f t e r r i t o r y . B i r d s t u d y 4:14-27'. 106 Tompa, Frank S. 1964„ Factors determining the numbers of song sparrows, Melospiza melodia (Wilson), on Mandarte Island, B. C , Canada. Acta Zool. Fenn. 109:1-73. U. So Department of Commerce, Weather Bureau. 1966. Climatological Data, Idaho. Annual Summary 67, No. 13. Wade, J. G. 1929. Mountain l i o n seen k i l l i n g a doe. C a l i f . Fish and Game, 15:73-75. Watson, G. W., and R. F. Scott. 1956. A e r i a l censuring of the Nelchina caribou herd. Trans. N. Am. Wildl. Conf. 21:499-509. Wood, Robert E. t / 1962. A productivity study of mule deer on the Middle Fork of the Salmon River, Idaho. Unpubl. Research Completion Report, Idaho Fish and Game Dept. 34 pp. Wright, Bruce S. 1960. Predation on big game i n East A f r i c a . J. Wil d l . Mgmt. 24:1-15. Young, Stanley P.9 and Edward A. Goldman. 1946. The puma, mysterious American cat. Am. Wildl. Institute. 358 pp. 107 APPENDIX \ 108 c^SJ / \ mfiLLBROCR k 'Jf'S ® EmnnlcE-i-.,-, i w'.TK \atA» CH PT. fcHORSE CR. BRIDGE ">V«:"7v-' lOMTQttt.O ! STODOflRO-DRIDGE TlTRRnCE v .23 ^ ' ' \ I -»^ v Jg&JWO POINT PK. f Sl .S* CD BRIOCl WILSOrVMTN YELLOW PINE ' -_cr^ if/ At* IB ^ q / ;i •SB* y ^ _ ___._mEUEBS COVE-0 . r t i « M » » . « -SnOUBHOE summiT— EnTgpncT--^BIG'SOLDKR KITH B ' " V % r : « ! l l R , B E f l R V n [ L E . y - . 1 ! jSsati/Vk dllDDtEJORKX/. „ SLEEPinG DEER _ CACHE CR BflSlfl „ ' \ ¥ i V'Z?/ inDipnsPR-raHRCR.i]-' , / IDAHO PRIMITIVE A R E A PAYETTE • BOISE • CHALLIS • SALMON NATIONAL FORESTS I D A M O 1 9 5 9 SCALE ^—L__^^J__^^J MILES L E C C N D i NATIONAL FOREST ---TRAILS. FI*E LOOKOUTS. «X LANDING STRIPS. © TELEPHONES. ROADS. & MMGEM I CUAIC STATIONS. ($ RADIOS. S t a t i s t i c a l Analysis of 16 Bone Marrow Specimens For Which Both Fresh and Dry Fat Content Had Been Determined* 109 Percent Fat, Dry Weight X Percent Fat, Fresh Weight Y Square Root Y Loge Y 25.49 2.54 1.59 .93 27.42 4 . 4 9 2.11 1.50 4 6 . 6 4 6.08 2.46 1.80 52.49 9.30 3.04 2.23 56,36 17.55 4.18 2.86 60.25 19.87 4.45 2.98 77.56 36.87 6.07 3 . 6 0 78.56 36.22 6.01 3.58 79.59 4 0 . 4 5 6.36 3.70 82.33 4 3 . 7 0 6.61 .3.77 84.11 44.37 6.66 3.79 8 8 . 8 4 60.61 7.78 4.10 8 9 . 4 2 52.07 7.21 3.95 91.10 76.30 8.73 4.3.3 92.69 72.14 8.49 4.27 94.33 7 0 . 4 0 8.39 4.25 Square root Y = .101 X - 1.5 Ln (Y) = .046 X - .042 Y = 0189 X 2 - 1. 297 X + 25.52 *Data supplied by Jerold Th[Lessen, B i o l o g i s t Idaho Fish and Game Department C o r r e c t i o n F a c t o r - Y = .0189 X - 1.297X + 25.52 - n o A p p l i e d to 33 Bone Marrow Specimens F o r Which O n l y Dry -Weight F a t C o n t e n t Was Known. Specimens C o l l e c t e d From L i o n - K i l l e d Deer and E l k P e r c e n t F a t , D r y Weight X 86.28 95.35 8 4 . 4 5 9 0 . 4 0 8 7 . 4 4 18.85 95.50 96.10 70.52 74.55 96.33 50.92 92.60 8 0 . 2 6 78.24 91.48 77.77 4 5 . 9 0 8 6 . 3 0 66.22 4 2 . 9 0 61.84 25.52 87.74 49.43 8 6 . 4 5 43.37 25.44 56.32 91.93 95.88 59.04 26.68 P e r c e n t F a t , A d j u s t e d Y 62.22 83.37 58.34 71.42 64.75 8.11 8 3 . 4 1 8 5 . 3 0 33.20 39.73 85.43 11.17 76.62 4 9 . 8 8 4 6 . 2 2 73.95 4 5 . 3 6 7.97 62.36 27.12 6.53 21.59 5.35 65.41 10.11 62.64 6.74 5.37 15.73 75.01 8 5 . 0 0 18.46 5.06 Anima1 C o n d i t i o n Good Good Good Good Good Poor Good Good P o o r Poor Good P o o r Good P o o r Poor Good P o o r Poor Good P o o r Poor Poor P o o r Good P o o r Good Poor Poor Poor Good Good Poor Poor Correction Factor - Y = .0189 X z - 1.297X + 25.52 -Applied to 14 Bone Marrow Specimens I^ or Which Only Dry -Weight Fat Content Was Known. Specimens Collected From Randomly Shot Deer and Elk Percent Fat, Percent Fat, Animal Dry Weight Adjusted Condition X Y 97.45 88.74 Good 97.58 8 8 . 9 1 Good 95.05 8 3 . 0 5 Good 96.59 8 5 . 6 1 Good 87.23 64.50 Good 45.47 7.0 Poor 90.44 71.44 Good 62.66 22.50 Poor 57.99 16.75 -Poor 98.13 90.49 Good 54.63 14.17 -Poor 33.10 4.38 Poor 8 3 . 2 4 55.87 Good 91.55 74.00 Good ) 112 C l a s s i f i c a t i o n o f 235 O c c u r r e n c e s o f Food Items i n 198 M o u n t a i n L i o n D r o p p i n g s Food Item No. O c c u r r e n c e s P e r c e n t O c c u r r e n c e Deer 132 56 Deer o r E l k 33 14 Snowshoe Hare • 13 5.5 G r a s s 12 5 Ground S q u i r r e l 6 2.5 Woodrat 5 2 P o c k e t Gopher 5 2 M o u n t a i n L i o n 5 2 Raccoon 4 1.7 Beaver 4 1.7 -Sedge 4 1.7 ' G r o u s e 3 1.3 U n i d e n t i f i e d B i r d s 3 1.3 G r a s s h o p p e r s 3 1.3 C o t t o n t a i l R a b b i t 2 .9 Peromyscus 1 .4 < Rl-2620-3 (Revised 5/66) BROWSE UTILIZATION (Reference FSH 2621.2 R l , chapter 100) Study area number Date 113 Forest D i s t r i c t Key species Herd and J u n i t Vegetation Dot t a l l y Form c l a s s 7 • 8 Examiner Pla n t No. Form c l a s s Age Leader Pla n t No. Form c l a s s Age c l a s s Leader use 1 2 3 4 5 6 c l a s s use 1. - 2 3 4 "5 6 1 2b 2 27 3 28 4 29 5 30 6 31 1 7 32 8 33 9 r 34 10 1 35 11 36 12 37 13 38 14 39 . 15 40 16 41 17 42 18 43 19 44 20 45 21 46 22 47 23 48 24 49 25 50 No. Percent Form Classes . 1 - A l l a v a i l a b l e , l i t t l e or no hedging 2 - A l l a v a i l a b l e , moderately hedged 3 - A l l a v a i l a b l e , severely hedged 4 - P a r t l y a v a i l a b l e , l i t t l e or no hedging 5 - P a r t l y a v a i l a b l e , moderately hedged 6 - P a r t l y a v a i l a b l e , s e v e r l y hedged 7 - Unavailable ) 8 - Dead ) Dot t a l l y (not included i n percentages) Age c l a s s e s S - Seedling Y - Young ) M - Mature ) R - Resprout D - Decadent ) Leader use, estimated percent Leader use, average 0 5 25 50 70 90 nonuse 1- 10 10- 40 40- 60 60-. 80 80- 100 114 Summary of Results Obtained From Sampling Six Key Winter Range Areas Big Creek 1967 Percent Plants in Form Class No Plants in Percent Plants in Form Class Age Class  Area 1 1 3 3 6 6 7 7 M D 9 9 84 8 70 14 78 4 78 22 74 18 58 8 78 6 76 2 88 82 66 68 6 10 22 2 • 6 2 16 2 . 2 2 22 6 8 18 10 10 34 32 17 21 11 14 11 13 20 15 3 5 11 13 10 15 21 17 10 14 25 23 21 19 19 16 42 28 30 34 54 12 14 62 24 24 60 16 8 74 18 22 64 14 20 70 10 28 52 20 8 56 36 32 48 20 12 70 18 10 74 16 Percent Use 90 90 90 90 90 90 90 90 90 90 90 90 115 Temporary Residents and Transients Captured on Established Ranges Adult Males Number 2 and 5, i n 1964-65, and Number 28 i n 1966-67, were captured i n the range of Number 3. Male Number 8, c l a s s i f i e d a temporary resident, was captured twice i n Number 3's range i n 1964p65. Male Number 20 was marked i n 1965-66 i n the areas occupied by Number 18. Male Number 9 was captured i n the same area as Number 7 this cat was l a t e r k i l l e d some 100 miles distant. Transient females captured i n these t e r r i t o r i e s are Numbers 1 and 32 i n Number 3's range, Number 21 i n the area occupied by Number 7, and Number 24 i n the area between these two ranges. Number 16, a temporary resident, was captured i n Number 18 1s t e r r i t o r y . Two adult males, Numbers 22 and 26, were captured i n the area i n Figure 1 between the ranges of Number 3 and Number 7. Another male ("X" i n Table V) was known to be i n this section i n 1966-67. Number 22 was d e f i n i t e l y a transient -- he was k i l l e d i n February, 1967, approximately 100 miles south of the study area. Number 26 or "X" may be resident on this area, although Number 26 was not recaptured and was believed a transient. 

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