Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Seasonal movements and foraging behaviour of resident killer whales (Orcinus orca) in relation to the… Nichol, Linda M. 1990

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1990_A6_7 N52.pdf [ 3.01MB ]
Metadata
JSON: 831-1.0098406.json
JSON-LD: 831-1.0098406-ld.json
RDF/XML (Pretty): 831-1.0098406-rdf.xml
RDF/JSON: 831-1.0098406-rdf.json
Turtle: 831-1.0098406-turtle.txt
N-Triples: 831-1.0098406-rdf-ntriples.txt
Original Record: 831-1.0098406-source.json
Full Text
831-1.0098406-fulltext.txt
Citation
831-1.0098406.ris

Full Text

SEASONAL MOVEMENTS AND FORAGING BEHAVIOUR OF RESIDENT KILLER WHALES fOrcinus orca) IN RELATION TO THE INSHORE DISTRIBUTION OF SALMON (Oncorhynchus spp.) IN BRITISH COLUMBIA By Linda M. Nichol B.Sc. (Zool.)/ University of B r i t i s h Columbia, 1985 A Thesis submitted i n p a r t i a l f u l f i l m e n t of the requirements for the degree of Master of Science In The Faculty of Graduate Studies (Department of Animal Science) We accept t h i s thesis as conforming to the required standard University of B r i t i s h Columbia July 1990 (§) Linda M. Nichol 1990 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of Animal Science The University of British Columbia Vancouver, Canada Date September 14, 1990 DE-6 (2/88) ABSTRACT Sightings and acoustic recordings from 1984 to 1989 of northern resident k i l l e r whales fOrcinus orca) from Johnstone S t r a i t o f f north eastern Vancouver Island and from King Island on the central B r i t i s h Columbia coast were analysed to examine the hypothesis that northern resident whales move seasonally i n t h e i r range to areas where salmon are available. K i l l e r whales were most abundant i n Johnstone S t r a i t between July and October and infrequent during the remainder of the year. The increase i n whale abundance during summer coincided with the migration of salmon (Oncorhynchus spp.) from offshore into Johnstone S t r a i t . The occurrence near King Island i n spring 1989 of the same resident whales that are seen i n Johnstone S t r a i t during summer, coincided with runs of sockeye and chinook salmon. During July, August and September of 1984 through 1988, k i l l e r whale sightings were recorded v i r t u a l l y d a i l y i n the Johnstone S t r a i t . Observations of k i l l e r whales i n Johnstone S t r a i t during the summer of 1988 showed that whales foraged along shore and i n areas of strong current where salmon occur i n high de n s i t i e s . Of the 16 k i l l e r whale pods i n the northern resident community, however, less than half were present more than 15% of summer days (1984 to 1988). Regression re s u l t s between numbers of whale days per week from each pod and numbers of salmon per week showed that the occurrence pods that were present on more than 15% of summer days i n Johnstone S t r a i t was p o s i t i v e l y and i i i s i g n i f i c a n t l y associated with the abundance of sockeye and pink salmon (six pods). In addition to these, the occurrence of one pod that spent less than 15% of summer days i n the S t r a i t was p o s i t i v e l y and s i g n i f i c a n t l y associated with chum salmon. Together these re s u l t s support the hypothesis that northern resident k i l l e r whales select t h e i r habitat seasonally to feed on available salmon. The res u l t s also lead to the hypothesis that within the northern resident community each pod has a seasonal home ranges. i v TABLE OP CONTENTS ABSTRACT i i LIST OF TABLES V LIST OF FIGURES. v i ACKNOWLEDGEMENTS v i i INTRODUCTION 1 METHODS 7 1) Study Animals 7 2) Study Areas 7 3) Sighting Records 9 4) Acoustic Records 14 5) Salmon Abundance Estimates 16 6) Estimating the Abundance of K i l l e r Whales i n Johnstone S t r a i t throughout the Year 17 7) Regression Analyses 19 8) Behavioural Sampling 20 RESULTS 2 3 1) Occurrence of K i l l e r Whales i n Johnstone S t r a i t Throughout the Year.. 23 2) Salmon Abundance and K i l l e r Whale Occurrence i n Johnstone S t r a i t 25 3) Salmon Abundance and K i l l e r Whale Occurrence Near King Island 29 4) Pod Usage of Johnstone S t r a i t During Summer 29 5) Regression Results Between the Occurrence of K i l l e r Whales and the Abundance of Salmon i n Johnstone S t r a i t 33 6) Behaviour of K i l l e r Whales 38 DISCUSSION 40 1) Occurrence of K i l l e r Whales and Salmon In Johnstone S t r a i t and Near King Island 40 2) The Relationship Between the Ocurrence of K i l l e r Whales and Salmon i n Johnstone S t r a i t During Summer 40 3) Foraging Behaviour of Resident K i l l e r Whales..42 4) Pod Home Ranges 46 CONCLUSION 52 LITERATURE CITED 53 V LIST OP TABLES Table I. Weeks of consecutive d a i l y observer e f f o r t i n Johnstone S t r a i t used i n analysis 13 Table I I . Months from which acoustic recordings were analysed and from which previously analysed data were used 15 Table I I I . Pods present i n Johnstone S t r a i t during d i f f e r e n t seasons of the year 1985 to 1989 27 Table IV. Numbers of salmon (in thousands) i n Johnstone S t r a i t , July to October, 1984 to 1988 30 Table V. Multiple regression r e s u l t s , between weekly numbers of whale days, from each northern resident pod, and weekly numbers of salmon i n Johnstone S t r a i t during July, August and September, 1984 to 1988 36 v i LIST OF FIGURES Figure 1. Map of B r i t i s h Columbia coastline showing ranges of the northern and southern resident k i l l e r whale communities, major salmon migratory routes and the two study areas 8 Figure 2. Map of Johnstone S t r a i t study area 10 Figure 3. Map of King Island study area 11 Figure 4. A comparison of the number of whales present i n Johnstone S t r a i t on 27 days during July, August and September of 1980, 1981, 1982 and 1983, estimated by v i s u a l observation and by acoustic monitoring 24 Figure 5. Mean number of whale days per month estimated from sightings and acoustic data i 2 6 Figure 6. Mean number of salmon (in thousands) and whale days per week i n Johnstone S t r a i t during July, August, September and October (1984 to 1988) 28 Figure 7. Frequency of occurrence of a l l or part of each northern resident pod seen i n the King Island study area during May and June 1989 31 Figure 8. Number of whale days each week i n the King Island study area during May and June 1989 32 Figure 9. Frequency of occurrence of a l l or part of each northern resident pod i n Johnstone S t r a i t during July, August and September, 1984 to 1988 34 Figure 10.Mean number of whale days per week during July, August and September, 1984 to 1988 35 Figure 11.Correlation between the percent time spent i n Johnstone S t r a i t by pods during July, August and September and the strength of the re l a t i o n s h i p with salmon 37 v i i ACKNOWLEDGEMENTS I would l i k e to thank Dr. David Shackleton, my supervisor for h i s support and encouragement. I would also l i k e to thank Dr. Kim Cheng for acting as my supervisor while Dr. Shackleton was on sabbatical. The members of my committee, Drs. A. Harestad, J . Ford and L. Gass also provided assistance through valuable c r i t i c i s m and discussion. To Dr. M. Bigg, a special thanks for taking an i n t e r e s t in my study and helping me at various points along the way. Dr. D. Bain, Dr. M. Bigg, J . Jacobsen, P. Spong and H. Symonds each gave me the use of t h e i r k i l l e r whale sighting records. Dr. J . Ford, P. Spong and H. Symonds also allowed me to use t h e i r acoustic recordings and C. Guinet allowed me to use h i s acoustic data. L. Hop-Wo, S. Hutchings, W. Luedke and P. Starr of the Canadian Department of Fisheries and Oceans provided data on salmon abundance. Q. Muelder ten Kate and J . Ripley assisted me i n the f i e l d i n 1988. In 1989, Dr. D. Bain, B. Kriete and myself combined forces to carry out a k i l l e r whale survey near King Island. I thank them both for including me i n t h i s venture. I would also l i k e to thank Jim and Ann Borrowman and B i l l and Donna MacKay of Telegraph Cove for giving support i n so many ways during both f i e l d seasons. Fin a n c i a l support was provided through a G.R.E.A.T. award from the B r i t i s h Columbia Science Council i n cooperation with the Vancouver Public Aquarium and by the Ann Vallee Ecological Fund. West Coast Whale Research and Education Foundation, generously gave me use of a Boston Whaler and outboard engine i n 1988. 1 INTRODUCTION Food influences patterns of movement, home range sizes, s o c i a l structure and t e r r i t o r i a l i t y i n many animals. Seasonal movements are common among mammals because food a v a i l a b i l i t y fluctuates seasonally i n v i r t u a l l y a l l habitats ( S i n c l a i r 1983). The si z e of areas over which individuals or groups range depends on food a v a i l a b i l i t y and d i s t r i b u t i o n (Macdonald 1983). Group sizes of predators and the evolution of cooperative hunting are related to prey type and hunting t a c t i c s (Kruuk 1975; Packer and Ruttan 1988). The occurrence of t e r r i t o r i a l i t y depends on the abundance and d i s t r i b u t i o n of a resource (in t h i s case food) and whether i t can be economically defended (Brown 1966). This thesis describes how salmon (Oncorhynchus spp.) abundance influences the movements and d i s t r i b u t i o n of resident k i l l e r whales (Orcinus orca) i n B r i t i s h Columbia. K i l l e r whales occur throughout most oceans i n both pelagic and coastal habitats (Dahlheim 1981; Leatherwood and Reeves 1983). The most detailed studies, however, have been conducted i n coastal B r i t i s h Columbia and northern Washington state (Balcomb et a l . 1982; Bigg 1982; Ford and Fisher 1982). These studies show that k i l l e r whales i n the P a c i f i c Northwest are highly s o c i a l and l i v e i n cohesive groups c a l l e d "pods" (Bigg et <al. 1987) . These pods form three s o c i a l l y i s o l a t e d communities with d i f f e r e n t ranges (Bigg et a l . 1987). The "northern resident community" ranges from mid Vancouver Island north to the Alaskan border. The "southern resident community" ranges from mid Vancouver Island south into Puget Sound and the S t r a i t of Juan de Fuca. The range of the "transient community" overlaps both resident ranges. Transients and residents do not mix but a c t i v e l y avoid each other (Bigg 1982). World-wide, k i l l e r whales eat a va r i e t y of f i s h , cephalopods, pinnipeds and other cetaceans (Hoyt 1984; Lowry et a l . 1987; Rice 1968). Within populations, however, k i l l e r whales may feed p r e f e r e n t i a l l y on s p e c i f i c prey types and move seasonally to areas where these prey are abundant (Heimlich-Boran 1986) . Early observers of k i l l e r whales i n Puget Sound and o f f northern Vancouver Island suggested that k i l l e r whales fed on salmon (Rice 1968; Spong et a l . 1970). Later studies (Bigg et a l . 1987) suggested that k i l l e r whales i n the northern and southern resident communities, feed on salmon and other f i s h because observations showed k i l l e r whales occurred predictably each summer i n s p e c i f i c areas within t h e i r ranges where salmon are abundant during summer. These s p e c i f i c areas are Johnstone S t r a i t , o f f north eastern Vancouver Island v i s i t e d by northern resident whales, and Haro S t r a i t , south of Georgia S t r a i t , v i s i t e d by southern resident whales. Both areas are along the salmon migration routes around Vancouver Island used by salmon returning to r i v e r s i n southern B r i t i s h Columbia (Groot and Quinn 1987; Gould et a l . 1988; Gould and Stefansson 1985). Transient k i l l e r whales, on the other hand, feed primarily on marine mammals, and Bigg et a l . (1987) observed that the seasonal movements of these whales were much less predictable 3 than those observed i n resident whales. Observations from other parts of the world suggest s i m i l a r seasonal s h i f t s i n k i l l e r whale d i s t r i b u t i o n s i n r e l a t i o n to prey. In the Indian Ocean, k i l l e r whales appear at southern fur seal (Arctocephalus spp.) and southern elephant seal (Mirounga leonina) rookeries during the breeding season (Condy et a l . 1978; V o i s i n 1972). Off the coast of Norway and around Iceland, k i l l e r whales are sighted most commonly inshore during the herring season (Jonsgard and Lyshoel 1970; Sigurjonsson et a l . 1988). S i m i l a r l y i n B r i t i s h and I r i s h waters, sightings of k i l l e r whales inshore coincide with the inshore migration of herring (Clupea spp.) and salmon (Salmo spp.) and with the breeding concentrations of grey seals (Halichoerus grypus) (Evans 1988). Off the east coast of Canada, k i l l e r whales appear to move north i n spring following the migration of rorquals (Balaenopteridae spp.) (Sergeant and Fisher 1957). L i t t l e has been done to quant i t a t i v e l y r e l a t e the movements of k i l l e r whales to those of t h e i r prey. This has been la r g e l y due to lack of data. Recent h i s t o r i c a l information, however, i s available on the movements of resident k i l l e r whales and of salmon i n the coastal waters of B r i t i s h Columbia and Washington State. These data provide a unique opportunity to q u a n t i t a t i v e l y r e l a t e movement patterns to prey abundance i n a k i l l e r whale population. Sighting records spanning many years provide data on the seasonal occurrence and d i s t r i b u t i o n of each resident k i l l e r whale pod. These data are available from many 4 researchers and are maintained i n a central database at the P a c i f i c B i o l o g i c a l Station i n Nanaimo, B r i t i s h Columbia (M. Bigg pers. comm.). Information on the abundance and migration c h a r a c t e r i s t i c s of salmon are available from the Canadian Department of Fisheries and Oceans (L. Hop-Wo pers. comm.; W. Luedke pers. comm.) and from the l i t e r a t u r e (Aro and Shepard 1967; Cooke and Groot, i n press; Gould et a l . 1988). Heimlich-Boran (1986) has made a quantitative analysis of the seasonal occurrence of southern resident k i l l e r whales over a three year period i n Haro S t r a i t and adjacent waterways. His r e s u l t s show that the occurrence of southern resident whales correlates p o s i t i v e l y with the abundance of salmon i n the area. Guinet (1990a) has shown a p o s i t i v e c o r r e l a t i o n between the occurrence of northern resident k i l l e r whales and the abundance of salmon i n Johnstone S t r a i t during one summer season. A quantitative i n depth study s i m i l a r to Heimlich-Boran's (1986) has not been made of the northern resident k i l l e r whales. In my study I examined the seasonal movements of each of the northern resident k i l l e r whale pods i n two areas of t h e i r range, Johnstone S t r a i t and King Island over a s i x year period. The purpose was to examine the hypothesis that k i l l e r whales feed on salmon and move seasonally throughout t h e i r home ranges to areas where salmon are abundant. I considered three predictions of t h i s hypothesis. 1) I f k i l l e r whales follow migrating salmon, then 5 they w i l l be seen more frequently i n Johnstone S t r a i t during summer months when salmon are abundant than during any other time of the year. Further, t h e i r occurrence i n the S t r a i t w i l l be p o s i t i v e l y related to numbers of salmon. To examine t h i s prediction, I used sightings and other available data to estimate the abundance of k i l l e r whales on a monthly basis throughout the year. I then regressed the number of whales present against the number of salmon, on a weekly basis during the salmon season. 2) The occurrence of k i l l e r whales w i l l be p o s i t i v e l y related to the occurrence of salmon i n other parts of the northern community range, p a r t i c u l a r l y when salmon are not abundant i n Johnstone S t r a i t . To examine t h i s prediction, I compared the occurrence of northern resident whales with estimates of salmon numbers during spring near King Island. 3) Foraging a c t i v i t y of k i l l e r whales i n Johnstone S t r a i t w i l l indicate that they are feeding primarily on salmon. To examine t h i s prediction, I observed k i l l e r whale behaviour and recorded where foraging occurred i n Johnstone S t r a i t and compared t h i s to the areas fished by commercial salmon fishermen. 6 Drawing on the r e s u l t s of these predictions I then develop the hypothesis that within the northern resident community, pods have t h e i r own seasonal home ranges. 7 METHODS 1) Study Animals In the northern resident community there are approximately 172 k i l l e r whales i n 16 "pods" (Bigg et a l . 1987). Pod: a group of individuals which t r a v e l together the majority of the time (Bigg et a l . 1990a). Pod membership i s stable over time. Pods range i n siz e from three to 23 ind i v i d u a l s . When pods do s p l i t temporarily, they do so into groups c a l l e d "subpods". Subpod: sub units of pods which also have stable membership. Members of subpods almost always t r a v e l together (> 95% of the time) (Bigg et a l . 1990a). There are one to three subpods per pod. The basic s o c i a l unit within subpods, and hence within pods, i s the "m a t r i l i n e a l group". M a t r i l i n e a l Group: A mother and her off s p r i n g including adult males but not adult daughters which have t h e i r own off s p r i n g . Daughters with offspring form t h e i r own m a t r i l i n e a l groups within the pod. Individuals always t r a v e l with members of t h e i r m a t r i l i n e a l group (Bigg et a l . 1990a). 2) Study Areas Northern resident k i l l e r whales were studied i n two coastal areas, 1) Johnstone S t r a i t , o f f north eastern Vancouver Island and 2) King Island, on the mainland approximately 180 km north of Johnstone S t r a i t (Fig. 1). a) Johnstone S t r a i t : The study area i s approximately 50 km from 8 130 125 0 130 125 Figure 1. Map of B r i t i s h Columbia coas t l ine showing ranges of the northern ( / / / / / ) and southern res ident k i l l e r whale communities (after Bigg et a l . 1987), major salmon migration routes (^^**^^ ) and the two study areas (Boxes). 9 east to west and the S t r a i t i s 3.5 to 4.5 km wide (Fig. 2). b) King Island: The study area encompasses Burke, Dean and Labouchere Channels a l l of which e n c i r c l e King Island and includes North Bentick Arm to the mouth of the B e l l a Cbola River. This i s a c i r c u i t of approximately 200 km and each channel i s approximately 3.5 to 4.5 km wide (Fig. 3). 3) Sighting Records A sighting record i s a report of a sighting of a subpod together with the date, location and the i d e n t i t y of the subpod. Bigg (1982) showed that k i l l e r whales can be i n d i v i d u a l l y i d e n t i f i e d by the unique shape of t h e i r dorsal f i n s and saddle patches, and by scars or nicks i n these two areas. A l l researchers use t h i s method to i d e n t i f y and report the in d i v i d u a l s or subpods they see. I compiled sightings of k i l l e r whales from records c o l l e c t e d over an 18-year period (1972 to 1989) mostly i n Johnstone S t r a i t but also from other parts of the northern community range. The majority of these sightings are stored i n a database at the P a c i f i c B i o l o g i c a l Station i n Nanaimo. Additional sightings were co l l e c t e d by myself and other observers. Combined there are over 4000 sighting records. Further references to t h i s dataset w i l l be made as " k i l l e r whale sighting database" (KWSD). a) Johnstone S t r a i t From the KWSD I selected d a i l y records from f i v e years, 1984 to 1988, to compare with salmon abundance. I chose 10 Figure 2. Map of Johnstone S t r a i t study area ( 11 12 these years because there was d a i l y observer e f f o r t over consecutive weeks during the summer months of July, August and September when salmon are abundant. During each summer, one to two research boats, two whale-watching boats and observers at a c l i f f s t a t i o n overlooking the S t r a i t (in radio contact with the boats) a l l monitored the study area. Not only were sightings of subpods reported, but days without whales were also reported. In t o t a l , I selected 61 weeks of consistent d a i l y records (Table I ) . In addition to d a i l y summer sighting records from Johnstone S t r a i t , I selected records from the KWSD for the non-summer months between January 1985 and February 1989. I combined these records with the summer sightings and with acoustic data (see below) to describe the annual pattern of k i l l e r whale occurrence i n Johnstone S t r a i t . Non-summer sighting records were co l l e c t e d i n c i d e n t a l l y and they provided no i n d i c a t i o n of observer e f f o r t because days without observers and days when whales were not seen were not recorded, b) King Island Sightings of k i l l e r whales near King Island were co l l e c t e d by myself and two other researchers (D. Bain and B. Kriete) between A p r i l 28 and June 12 1989. In addition to recording the i d e n t i t y of subpods seen, we recorded days without whales and days without observer e f f o r t . Over the 46 days of t h i s survey, 10 days were l o s t to bad weather, engine d i f f i c u l t i e s and supply runs. 13 Table I: Weeks of consecutive d a i l y observer e f f o r t i n Johnstone S t r a i t used i n analysis. Year F i r s t week Last Week Total Weeks 1984 July Sept. 1st week 2nd week 11 1985 June Sept. 4th week 4th week 14 1986 June Sept. 4th week 4th week 14 1987 July Aug. 3rd week 4th week 7 1988 June Oct. 4th week 1st week 15 Total 61 14 4) Acoustic Records Sighting records provide one source of data to monitor k i l l e r whale presence and movements. Another source are acoustic recordings of the vocalizations produced by the whales. Ford and Fisher (1982) determined that each resident k i l l e r whale pod produces a repertoire of eight to 15 discrete c a l l s . Some pods share c a l l s but each has a unique d i a l e c t . Pods can be i d e n t i f i e d by spectral analysis of taped recordings of t h e i r underwater sounds and comparing these with i d e n t i f i e d pod-specific c a l l s . I analysed acoustic recordings made during non-summer months at Orca Lab (a permanent acoustic monitoring st a t i o n on Hanson Island) and at Telegraph Cove (on Vancouver Island). As with inc i d e n t a l sightings, monitoring e f f o r t was not always known. Orca Lab monitors three to four hydrophone i n s t a l l a t i o n s located i n Blackney Pass and Johnstone S t r a i t (Spong and Symonds 1990). At Telegraph Cove, the hydrophone i s located at the entrance to the cove and monitors Johnstone S t r a i t and Weynton Pass (J. Ford pers. comm.). The recordings I analysed represented 52 days from non-summer months from 1986 to 1989. In addition I used data c o l l e c t e d and analysed by Guinet (1986) and J . Ford (unpublished) from 1985 and 1986 respectively (Table I I ) . Recordings were analysed using a Kay DSP spectrum analyser, model 5500. Pod-specific c a l l s were i d e n t i f i e d by comparing the screen display of a c a l l structure with the c a l l parameters documented by Ford (1987) and by aural comparison with 15 Table I I : Months from which acoustic recordings were analysed and from which previously analysed data were used. Year Months Monitorincr location 1985* 1985** January, A p r i l October November December T.C. O.L. 1986** January, February, March, A p r i l , May June O.L. 1986 March, June October O.L., T.C. 1987 September, October, November, December O.L. 1988 October, November, December O.L. 1989 January, February O.L. * acoustic data previously analysed (J. Ford unpubl. data). Used with permission, (Ford pers. comm.) ** acoustic data previously analysed (Guinet 1986). Used with permission (Guinet pers. comm.) T.C. = Telegraph Cove on Vancouver Island O.L. = Orca Lab on Hanson Island 16 previously recorded and i d e n t i f i e d examples. 5) Salmon Abundance Estimates a) Johnstone S t r a i t The Canadian Department of Fisheries and Oceans i n Nanaimo (L. Hop-Wo pers. comm.; W. Luedke pers. comm.) provided estimates of the number of sockeye (0. nerka), pink (0. crorbuscha) and chum (0. keta) salmon passing through Johnstone S t r a i t on a weekly basis during July, August, September and October from 1984 to 1988. Each estimate for each salmon species i n each year i s calculated from three pieces of information: i) The t o t a l size of the run that passed through Johnstone S t r a i t . This i s calculated as the catch plus the escapement. The escapement i s salmon which escape the fishery and ar r i v e at the mouth of t h e i r spawning r i v e r . i i ) The migration pattern, or the percent of the t o t a l run that passed through the S t r a i t during each week of the migration. This i s estimated from average h i s t o r i c a l escapement curves and the run reconstruction method (See Hilborn and Starr 1988) . i i i ) The date of the peak of the migration through Johnstone S t r a i t . This i s estimated from t e s t f i s h i n g r e s u l t s . The date of the peak catch estimates the date of the peak of the migration. Chinook (0. tschawytscha) and coho (0. kisutch) salmon also occur i n Johnstone S t r a i t during summer months but they are much less abundant than sockeye, pink, and chum and are not 17 considered commercially important i n the area. Consequently the Canadian Department of Fisheries and Oceans has no estimate of t h e i r numbers or migration timing (P. Starr pers. comm.), and so I was unable to include these salmon i n my analyses, b) King Island The Canadian Department of Fisheries and Oceans i n B e l l a Coola (S. Hutchings per. comm.) provided catch and escapement data on sockeye, pink, chinook and chum, as well as estimates of the periods of peak abundance for each species i n the area. From the catch and escapement data I estimated the t o t a l number of each salmon species i n the study area during spring. Unlike Johnstone S t r a i t , there are no estimates of weekly abundance. 6) Estimating the Abundance of K i l l e r Whales i n Johnstone S t r a i t  Throughout The Year The d a i l y sighting records from summer months and the acoustic data and incidental sightings covering the rest of the year represented 3 6 months between January 1985 and February 1989. These data were used to calculate the average number of whales present during each month of the annual cycle, a) Acoustic Versus Visual Estimates of Whale Abundance Estimates of whale abundance during non-summer months were derived mainly from acoustic recordings whereas summer estimates were derived from sightings. I t was important, therefore, to compare estimates of whale abundance derived by the 18 two methods when col l e c t e d simultaneously, to determine i f they could be used interchangeably to estimate whale abundance throughout the year. I compared the pods i d e n t i f i e d a c o u s t i c a l l y with those i d e n t i f i e d v i s u a l l y using acoustic data already analysed ( J . Ford unpubl. data) and the corresponding sightings (KWSD) from a t o t a l of 27 days i n July and August of 1980 to 1983. The acoustic recordings were made from a boat and were c o l l e c t e d simultaneously with the sighting records. A comparison of the pods detected a c o u s t i c a l l y with those detected v i s u a l l y , tests the l i k e l i h o o d that k i l l e r whales vocalize when present. The number of whales estimated by each method, assuming that a l l members of a pod were present, was then compared i n a simple regression using analysis of variance to t e s t the s i g n i f i c a n c e of the r e l a t i o n s h i p (Wilkinson 1988: 475; Zar 1984: 268). I used the student t - t e s t to t e s t whether the slope of the regression d i f f e r e d from 1.0 (Zar 1984: 271). b) Estimating Numbers of Whales Visual data show that pods sometimes s p l i t into subpods which may t r a v e l separately for up to a month (Bigg et a l . 1990a). K i l l e r whale vocalizations allow i d e n t i f i c a t i o n of pods but not which of t h e i r subpods are actually present. Furthermore, Gl and G12 pods are not yet distinguishable a c o u s t i c a l l y . To account for t h i s l i m i t a t i o n of acoustic data, I assumed for the purposes of t h i s analysis that when a pod was i d e n t i f i e d a c o u s t i c a l l y a l l members of the pod were present. In 19 the case of Gl and G12 pods, when "G" c a l l s were i d e n t i f i e d I assumed both pods were present. For comparative purposes i n t h i s analysis only, I converted summer sighting of subpods to pods when at l e a s t one subpod of a pod was present. Multiple sightings on one day, of subpods belonging to one pod were counted as only one sighting. The pod present was then converted to the t o t a l number of whales i n that pod because pod sizes vary greatly i n the northern resident community. I then considered each whale from the pod present on one day as one 11 whale day" and summed the number of whale days for each month. Each month of the year was represented by at least 2 years of data (with the exception of May for which there was only 1 years data). I calculated the mean number of whale days each month i n the annual cycle by averaging r e p l i c a t e months between January 1985 and February 1989. 7) Regression Analyses a) Johnstone S t r a i t I used only the 61 weeks of d a i l y k i l l e r whale sighting records from the summers of 1984 to 1988 (Table 1). I computed a regression s t a t i s t i c between numbers of whales present and numbers of salmon present for each of the 16 northern resident pods. I converted each sighting of a subpod d i r e c t l y to the number of whales i n that subpod. This can be done with the assumption that a l l members of the subpod are present because members of subpods t r a v e l together greater than 95% of the time 20 (Bigg et a l . 1990a). Each whale present on one day represented one "whale day". I then summed the number of whale days each week for each of the 16 northern resident pods. Then t r e a t i n g each pod separately, I regressed the number of whale days per week against weekly numbers of each salmon species (sockeye, pink and chum) i n a multiple regression analysis. Analysis of variance was used to t e s t the s i g n i f i c a n c e of each multiple regression (Wilkinson 1988: 480; Zar 1984: 335). I present both the c o e f f i c i e n t of multiple determination (R2) and the corresponding multiple c o r r e l a t i o n c o e f f i c i e n t (R) for comparative purposes with other studies, b) King Island The co-occurrence of k i l l e r whales and salmon i n t h i s area was examined q u a l i t a t i v e l y because weekly estimates of salmon numbers were not available. 8) Behavioural Sampling a) Observations Between July 7 and September 1, 1988, I observed k i l l e r whales i n Johnstone S t r a i t and recorded where they foraged and the amount of time they spent in d i f f e r e n t a c t i v i t i e s . A subpod was located and observed at a minimum distance of 100 m. I increased observation distances to at l e a s t 300 m when the whales entered the Robson Bight Ecological Reserve because they are very sensitive to disturbance when rubbing (Briggs 1987). Observation sessions ranged from 3 to 8 h. 21 Sessions were terminated a f t e r a maximum of 8 h to avoid observer fatigue, while shorter sessions were terminated by weather and sea conditions, time of day or movement of the whales out of the study area. The behaviour of each i n d i v i d u a l i n the group was observed and recorded at 15 min scan i n t e r v a l s (Altmann 1974). The d i r e c t i o n of t r a v e l of the whales and t h e i r p o s i t i o n r e l a t i v e to landmarks and distance from shore were also recorded on a de t a i l e d map of the study area. I c l a s s i f i e d the behaviour of the whales into one of f i v e main behavioural categories, foraging, t r a v e l l i n g , s o c i a l i z i n g , resting and rubbing. These behaviours have been defined by recognizable surface behaviours, surfacing i n t e r v a l s and the degree of group synchrony i n r e s p i r a t i o n (Ford 1988; Jacobsen 1986; Osborne 1986) . Foraging: Whales i n the group are spread out often as much as several hundred metres along the shore or within a few hundred metres of shore. Individuals swim i n the same general d i r e c t i o n p a r a l l e l to shore but surface asynchronously. B r i e f bouts of e r r a t i c swimming indicate pursuit of prey. T r a v e l l i n g : Whales i n the group swim abreast of each other and surface synchronously. Resting: As i n t r a v e l l i n g , whales swim abreast and indiv i d u a l s surface synchronously. Their horizontal progress i s very slow, however, and surfacings are frequently followed by b r i e f periods of surface f l o a t i n g during which members of the group f l o a t with t h e i r blowholes exposed. S o c i a l i z i n g : Individuals make physical contact while chasing, breaching and r o l l i n g over each other. Other surface behaviours observed include fluke slaps, pectoral slaps, breaches, penis displays and spyhops. Rubbing: Individuals i n the group rub t h e i r bodies on the smooth pebble substrate at s p e c i f i c beaches i n the Robson Bight Ecological Reserve, b) A c t i v i t y Budget During each 15 min in t e r v a l the behaviour of the group was taken as the behaviour exhibited by the majority (> 50%) of the individuals i n the group (Ford 1988). In a l l sample sessions t h i s c r i t e r i a was met, which r e f l e c t s the fact that whales within a subpod t y p i c a l l y engage in the same behaviour at the same time. To determine the percent of time whales spent engaged i n each behaviour I calculated the t o t a l time spent i n each behaviour over a l l sessions and divided t h i s by the t o t a l minutes of observation over a l l sessions. RESULTS I begin with a comparison of acoustic and v i s u a l estimates of whale abundance. I then present the pattern of k i l l e r whale occurrence i n Johnstone S t r a i t throughout the year and i n more d e t a i l the temporal pattern during summer months of both whales and salmon. I then present the temporal pattern of k i l l e r whale and salmon numbers i n the King Island study area. From considering a l l whale sightings combined, I next consider whale sightings from each pod. I examine how much time each pod i n the northern resident community spends i n Johnstone S t r a i t during summer. I then present the regression r e s u l t s between the occurrence of whales from each pod and numbers of salmon i n the S t r a i t . F i n a l l y , I describe the behaviour of whales i n both the Johnstone S t r a i t and King Island study areas. 1) Occurrence of K i l l e r Whales i n Johnstone S t r a i t Throughout the  Year A comparison of acoustic and v i s u a l estimates of whale abundance (Fig. 4) shows that, with s i m i l a r l e v e l s of e f f o r t and the assumption that a l l members of a pod are present, the two methods provide s i m i l a r estimates of whale numbers (r 2 =0.78 P<0.001, n=27). The acoustic method, however, under-estimated s l i g h t l y the number of whales, because not a l l pods i d e n t i f i e d v i s u a l l y vocalized during some recording sessions or they were out of range of the recording equipment. This i s r e f l e c t e d i n the slope of the regression equation which i s s i g n i f i c a n t l y less than 24 100 - i 80 -"5 CO CD O -*—» CO Z3 o o < 60 -40 -20 0 0 20 40 60 Visual estimate 80 100 Figure 4. A comparison of the number of whales i n Johnstone S t r a i t on 27 days during J u l y , August and September of 1980, 81, 82 and 83 estimated by v i s u a l observation and by acoust ic monitoring. r 2=0.78, P<0.001, n=27 days, s lope<l , P<0.05, Y=3.95+0.78X. 25 1.0 (slope = 0.78, t - t e s t : P < 0.05, Y = 3.95 + 0.78X). Nonetheless, I have combined sightings and acoustic data from January 1985 to February 1989. These data show that k i l l e r whales are most abundant i n Johnstone S t r a i t during summer (July to October) and are least abundant between December and June (Fig. 5). Furthermore, k i l l e r whales are not only less frequent i n Johnstone S t r a i t outside of summer, but only a few pods seem to v i s i t the area (Table I I I ) . 2) Salmon Abundance and K i l l e r Whale Occurrence i n Johnstone  S t r a i t The timing of salmon migrations, e s p e c i a l l y of pink and sockeye, through Johnstone S t r a i t during July, August and September coincides well with the occurrence of k i l l e r whales (Fig. 6). During these months sockeye and pink salmon peak i n abundance between la t e July and mid August, chum salmon peak i n abundance i n early October while k i l l e r whales sightings peak between l a t e July and early September. Total numbers each summer of these three salmon species have varied from four to 15 m i l l i o n (1984 to 1988) (salmon estimates provided by the Canadian Department of Fisheries and Oceans, L. Hop-Wo pers. comm.; W. Luedke pers. comm). Interannual v a r i a t i o n i n salmon numbers res u l t s because d i f f e r e n t stocks of each species return i n di f f e r e n t years and stock sizes vary. In a si m i l a r manner, the number of salmon during the peak of the migration varied. Numbers of sockeye during weeks of peak abundance ranged from 150,000 to 26 n= 3 2 2 2 1 3 4 4 4 4 4 3 months 1500 - i GO > "a J32 ctf CD E c c co CD 1000 -500 0 M I A M Y J U J L A U T S T 0 T N D Months Figure 5. Mean number of whale days per month estimated from s ight ings and acoust ic data. Bars represent means. V e r t i c a l l i n e s represent standard e r r o r of the mean, n = number of r e p l i c a t e months (1985 -1989). 27 Table I I I : Pods present i n Johnstone S t r a i t during d i f f e r e n t seasons of the year (1985 - 1989). Pods i d e n t i f i e d from both v i s u a l and acoustic records. July - October November - June Al A l A4 A4 A5 A5 BI CI CI G1/G12 Dl 111 G1/G12* 131 HI 11 12 111 118 131 Rl Wl * G1/G12 = Gl and/or G12 because these pods are not yet distinguishable a c o u s t i c a l l y . 28 Figure 6. Mean number of salmon and whale days per week i n Johnstone S t r a i t during J u l y , August, September and October. • numbers of sockeye i n thousands. numbers of pink i n thousands, x numbers chum i n t h o u s a n d s . © numbers of k i l l e r whales, n = 5 summers (1984 - 1988). 29 1.4 m i l l i o n per week between 1984 and 1988. During weeks of peak abundance, numbers of pink ranged from 250,000 to 2 m i l l i o n per week and numbers of chum salmon ranged from 280,000 to 700,000 per week (Table IV). 3) Salmon Abundance and K i l l e r Whale Occurrence Near King Island Between l a t e - A p r i l and mid-June, neither k i l l e r whales nor salmon are abundant i n Johnstone S t r a i t . Near King Island, however, k i l l e r whales from nine northern resident pods, A l , A4, A5, CI, Dl, G12, I I , 12 and Rl, which a l l v i s i t Johnstone S t r a i t during the summer, were observed for 3 6 days between A p r i l 28 and June 12 1989 (Fig. 7). At the same time, there were salmon i n the King Island area and the predominant runs were of sockeye and chinook (Fig. 8). Chinook salmon were present i n these channels during early A p r i l with the majority returning to the B e l l a Coola River system. The number of returning chinook i s estimated to have been about 3 0,000, with peak numbers i n the channels by mid-June (S. Hutchings pers. comm.). Sockeye salmon, migrating to the Bell a Coola River at the head of North Bentick Arm and to the Kimsquit River at the head of Dean Channel appeared i n Burke and Dean Channels i n mid-May, and peaked i n abundance by early July (S. Hutchings pers. comm). The t o t a l number of returning sockeye was about 38,000 salmon. 4) Pod Usage of Johnstone S t r a i t During Summer Although i n general, k i l l e r whales are most abundant i n Table IV: Numbers of salmon (in thousands) in Johnstone S t r a i t July to October, 1984 to 1988 from the Canadian Department of Fisheries and Oceans estimates (L. Hop-Wo pers.comm; W. Luedke pers.comm.). Total numbers of each species and the peak weekly number of each species. TOTAL JULY to OCTOBER PEAK WEEK Year Sockeye Pink Chum Sockeye Pink Chum 84 1796 820 1838 636 241 285 85 4398 7739 3667 1387 2045 570 86 3492 1756 738 1119 566 696 87 2379 2804 1924 659 779 298 88 546 2624 3195 155 818 895 31 100 -i 80 -00 cd "a c o =S 60 cd > CD" 00 o c CD O i _ CD Q_ 40 20 -0 A5 1 12 T C1 D1 T R1 A1 Pods r ? A 4 G1 IT Figure 7. Frequency of occurrence of a l l or part of each northern res ident pod seen i n the King Is land study area during May and June 1989. n = 36 days of observations. Pods are arranged from most frequent to l eas t frequent. 32 n • 150 6 6 4 6 6 days CO & 100 TJ CD E 50 -0 chinook May Weeks June sockeye v/////;/////;/~x Figure 8. Number of whale days each week i n the King Is land study area during May and June 1989. n = number of observation days each week. Hor izonta l bars = weeks when chinook and sockeye were present. Arrow = week of peak chinook abundance. Johnstone S t r a i t during July, August and September (Fig. 5), only whales from A l and A5 pods were present i n Johnstone S t r a i t on more than 50% of the days during these months (1984 to 1988). Most other pods spent considerably less time i n the S t r a i t (Fig. 9). Consequently, peak weekly numbers of whale days during summer represents only about 25% of the northern resident population. I f the entire northern resident community were present there should have been about 1204 whale days per week (172 whales * 7 days), whereas the peak number of whale days was 413 or an average of 277 whale days per week (Fig. 10). 5) Regression Results Between the Occurrence of K i l l e r Whales and  the Abundance of Salmon i n Johnstone S t r a i t When considered i n d i v i d u a l l y , sightings of seven of the 16 pods i n the northern resident community were p o s i t i v e l y and s i g n i f i c a n t l y associated with estimates of one or more! species of salmon. The occurrence of three of these pods, A l , A5,j and CI, associated p o s i t i v e l y with sockeye and pink salmon, while the occurrence of A4, Dl and HI associated p o s i t i v e l y with only sockeye and Gl pod associated p o s i t i v e l y with only chum salmon (Table V). The more time pods spent i n Johnstone S t r a i t during July, August and September (data from Fig. 9), the stronger was the regression (Fig. 11, r =0.83, p<0.001, n=16) with salmon numbers (data from Table V). Of the six pods whose occurrence were p o s i t i v e l y related to sockeye and pink salmon, a l l were present on more than 15 % of summer days i n Johnstone S t r a i t . The 34 100 - i c CD 00 CD 00 CO 80 -60 c CD O i _ CD Q_ 40 -20 -0 n n n JZL i T i i i i \ i i i i — i — i — i — i — r A1 A5 C 1 A4 D 1 H 1 131 B 1 R 1 W1 G 1 2 111 118 G 1 2 11 Pods Figure 9. Frequency of occurrence of a l l or part of each northern res ident pod i n Johnstone S t r a i t during J u l y , August and September, 1984 to 1988. Bars represents percent of a l l observation days from 1984 to 1988 (n = 403 days) . r 35 n = 4 5 5 5 5 5 5 5 5 5 4 4 4 weeks 3 0 0 n 0 i i i i i i i i i i July Aug Sept Weeks Figure 10. Mean number of whale days per week during July, August and September. Dots represent means. V e r t i c a l l i n e s represent standard error of the mean, n = number of r e p l i c a t e weeks 1984 - 1988. 36 Table V. Multiple regression r e s u l t s between weekly numbers of whale days from each northern resident pod and weekly numbers of three species of salmon, i n Johnstone S t r a i t during July, August and September, 1984 to 1988 (n=61 weeks). R2 = the c o e f f i c i e n t of multiple determination for each pod, R = the multiple c o r r e l a t i o n c o e f f i c i e n t , n = the number of weeks of whale sightings and salmon abundance data used i n each regression. Salmon = those species which contributed s i g n i f i c a n t l y i n each multiple regression. POD R2 R n Salmon A l 0.28** 0.53** 61 S, P A4 0. 10* 0.32* 61 S A5 0.37** 0.61** 61 S, P Bl 0. 04 0.19 61 CI 0.35** 0. 59** 61 S, P Dl 0. 10* 0.31* 61 S Gl 0. 10* 0.32* 61 c G12 0. 05 0.22 61 HI 0.17* 0.41* 61 S 11 0.01 0 . 12 61 12 0. 03 0. 18 61 111 0. 06 0.24 61 118 0. 07 0. 27 61 131 0. 04 0.20 61 RI 0.06 0.25 61 Wl 0. 04 0.20 61 ** P < 0.001 * P < 0.01 S = Sockeye, P = Pink, C = Chum 37 ' C o "ca c "E "5 •o a? a. 0.4 n C1, 0.3 -0.2 -H1. , A5 A1 c Q 'o ^ 0.1 -CD O o G1i A4 # D1 # 0.0 - f 0 20 40 60 Percent presence 80 100 Figure 11. C o r r e l a t i o n between the percent time spent i n Johnstone S t r a i t by pods during J u l y , August and September and the s trength of the regress ion with salmon. r=0.83, p<0.001, n=16. Points represent ing pods with s i g n i f i c a n t , p o s i t i v e r e l a t i o n s h i p s with salmon abundance are l a b e l l e d with the pod's name (see Table V ) . 38 whales i n these pods represent 3 5% of the northern resident community (approximately 59 whales). For whales which spent less than 15% of summer days i n the S t r a i t , the occurrence of only Gl pod was p o s i t i v e l y related to salmon abundance and t h i s was with chum salmon. Gl pod represents an additional 13% of the community (approximately 2 3 whales). Combined, numbers of whale days from these seven pods constituted the majority of weekly whale days between 1984 and 1988 (X=87.6%, S.E.M.=1.52, n=59). The occurrence of the remaining nine pods, BI, G12, I I , 12, 111, 118, Rl and Wl (approximately 9 3 whales or 52% of the community) did not r e l a t e s i g n i f i c a n t l y to salmon abundance and a l l spent less than 15% of summer days i n the S t r a i t . 6) Behaviour of K i l l e r Whales a) Johnstone S t r a i t A t o t a l of 13 3 h of observations were made of two subpods, A12 and A2, of the Al pod during 22 d a i l y sessions between July 7 and September 1, 1988. Of a l l the northern resident pods, A l pod whales use Johnstone S t r a i t the most during summer (see Fi g . 9) and tend to stay within the study area for extended periods making i t possible to follow them for 4 to 8 h sessions. K i l l e r whales foraged along the Vancouver Island shore from Robson Bight to Blinkhorn Point, a distance of about 13 km. The whales also forage along West Cracroft Island, Hanson Island and i n the strong current at the junction of Blackney Pass and 39 Johnstone S t r a i t . Pursuit of prey by k i l l e r whales was evident by t h e i r b r i e f bouts of e r r a t i c swimming. Other researchers and I made 5 d i r e c t observations of salmon being pursued or captured by k i l l e r whales i n these shoreline areas: on two occasions I observed A l pod whales capturing salmon; J . Jacobsen (pers. comm.) observed A5 whales on two occasions and a CI whale on one occasion, corner salmon i n rock crevices along the shore. The proportion of time spent i n each behaviour category was: foraging 38%, t r a v e l l i n g 32%, resting 15%, s o c i a l i z i n g 12% and rubbing 3%. b) King Island Although detailed behavioural observations were not made i n t h i s area, k i l l e r whales swam mainly along shorelines and frequently moved long distances. For example, on eight occasions when k i l l e r whales were tracked for six to 10 h, they t r a v e l l e d distances of 40 to 85 km. Furthermore, resighting of the same whales occurred i n a l l parts of the approximately 200 km long study area around King Island, providing further evidence that the whales were t r a v e l l i n g long distances on a d a i l y basis. This i s i n s t r i k i n g contrast to t h e i r movements i n Johnstone S t r a i t during summer, which are very l o c a l i z e d . 40 DISCUSSION 1. Occurrence of K i l l e r Whales and Salmon i n Johnstone S t r a i t and  Near King Island Despite the varying quality of data used to describe the occurrence of k i l l e r whales i n Johnstone S t r a i t throughout the year, the seasonal d i s t r i b u t i o n of k i l l e r whales i s consistent with the impressions of researchers and tour operators who have worked i n Johnstone S t r a i t over the past 18 years (M. Bigg pers. comm.; B. MacKay pers. comm.). The annual increase i n whale occurrence i n the S t r a i t during the salmon season (July to October) supports the hypothesis that northern resident k i l l e r whales select t h e i r habitat seasonally i n response to the temporal a v a i l a b i l i t y salmon. The occurrence i n the King Island study area of the same northern resident pods that v i s i t Johnstone S t r a i t during summer coincided with l o c a l spring runs of sockeye and chinook salmon, providing additional support for t h i s hypothesis. Southern resident k i l l e r whales appear to behave s i m i l a r l y , using t h e i r habitat seasonally i n response to salmon (Heimlich-Boran 1986). 2. The Relationship Between the Occurrence of K i l l e r Whales and  Salmon i n Johnstone S t r a i t During Summer The p o s i t i v e and s i g n i f i c a n t relationships between the occurrence of k i l l e r whales and of salmon i l l u s t r a t e s s t a t i s t i c a l l y that the seasonal occurrence of k i l l e r whales i n 41 Johnstone S t r a i t i s explained i n part by the seasonal abundance of salmon. Although s t a t i s t i c a l l y s i g n i f i c a n t , none of the c o e f f i c i e n t s of multiple determination, nor the corresponding c o r r e l a t i o n c o e f f i c i e n t s are very high. However, comparing the co r r e l a t i o n c o e f f i c i e n t s with those reported by Heimlich-Boran (1986) for the southern resident community, and by Guinet (1990a) for the northern resident community, my re s u l t s are s i m i l a r to there's. In considering the v a r i a t i o n unaccounted for i n these relationships i t i s important to recognize that k i l l e r whales are probably highly e f f i c i e n t predators which can use sight and sonar to locate prey and then move with speed and a g i l i t y to capture them. Consequently small changes i n ov e r a l l salmon numbers may be unimportant to the whales. Salmon estimates may be another source of v a r i a t i o n which i s unaccounted for i n the regressions because the estimated number of salmon per week i s l i k e l y inaccurate to some degree. This error i s related to the migration curves used by the Department of Fisheries and Oceans to make weekly estimates of salmon abundance. The migration curve for each salmon species i s an average derived from the migration curves of a l l stocks of a species that passes through Johnstone S t r a i t . For example, both chum salmon and even-year pink salmon passing through the S t r a i t are comprised lar g e l y of a mixture of stocks destined for d i f f e r e n t r i v e r s along the south coast of B r i t i s h Columbia (Aro and Shepard 1967; Gould et a l . 1988). In d i f f e r e n t years, the number of salmon from each stock of a species can vary and thus 42 the composite migration curve for a species w i l l be inaccurate i n shape and therefore i n i t s value of weekly salmon numbers (W. Luedke pers. comm.). Unforunately, the amount of error from t h i s source i s unknown (W. Luedke pers. comm.). The sport f i s h i n g catch data used by Heimlich-Boran (1986) to correlate the occurrence of southern resident whales with salmon abundance are also l i k e l y to have provided inaccurate estimates of weekly salmon numbers, because he did not used any measure of f i s h i n g e f f o r t . S i m i l a r l y , Guinet (1990a) used commercial catch data without any measure of f i s h i n g e f f o r t i n his single season c o r r e l a t i o n of northern resident whales. Nonetheless, despite inaccuracies in each of our salmon data sets, my re s u l t s are consistent with t h e i r s , and combined our res u l t s i l l u s t r a t e that a seasonal rel a t i o n s h i p does e x i s t between resident k i l l e r whales and salmon i n coastal B r i t i s h Columbia and northern Washington. 3) Foraging Behaviour of Resident K i l l e r Whales The observations of k i l l e r whales pursuing and eating salmon while i n the Johnstone S t r a i t , which I reported, provides evidence, i n addition to the regression r e s u l t s , that the occurrence of whales and salmon i n Johnstone S t r a i t r e f l e c t s a predator-prey re l a t i o n s h i p . Similar observations of foraging whales have been made i n the southern resident community (Heimlich-Boran 1986). In addition to observations of foraging behaviour, there i s evidence from f i s h scales c o l l e c t e d on the water near foraging resident k i l l e r whales to indicate that 95% 43 of detected k i l l s are of salmon (Bigg et a l . 1990b). My observations of k i l l e r whales i n A l pod showed that they foraged primarily along shorelines and i n areas of strong current. Around King Island, k i l l e r whales were also observed to swim mainly along the shore. There are at least two possible reasons for foraging i n shoreline areas: 1) Areas where salmon t r a v e l close to shore may be important to k i l l e r whales because they are able to use the shore as a b a r r i e r against which to trap salmon (Jacobsen 1986; Ford 1989). Johnstone S t r a i t and Burke, Dean and Labouchere Channels, a l l have steep sides which may make them even better areas for trapping salmon. Underwater observations of k i l l e r whales cornering salmon i n rock crevices i n Johnstone S t r a i t (J. Jacobsen pers. comm.) support t h i s potential advantage of steep shorelines. Southern resident k i l l e r whales forage s i g n i f i c a n t l y more in areas with high r e l i e f subsurface topography and shallow reefs along salmon migratory routes (Heimlich-Boran 1988). These are areas where salmon could be e a s i l y herded into higher densities (Heimlich-Boran 1988). K i l l e r whales o f f Argentina and o f f the Crozet Islands use shorelines as ba r r i e r s when hunting southern sea l i o n s (Otaria flavescen) and southern elephant seals (Mirouncra  leonina). These whales i n t e n t i o n a l l y beach themselves and capture t h e i r mammalian prey at the water's edge. Hunting success i s higher with t h i s technique than in open water where pinnipeds are faster and more ag i l e than on land (Lopez and Lopez 1985; Guinet 1990b). The use of bar r i e r s to herd and capture prey has also been described i n studies of bottlenose dolphins (Tursiops  truncatus) (Wursig 1986; Irvine et a l . 1981). 2) Commercial f i s h i n g a c t i v i t y , catch data and ul t r a - s o n i c tagging of salmon a l l suggest that the types of areas where k i l l e r whales forage most i n Johnstone S t r a i t are areas of high salmon densities (Cooke and Groot, i n press; Gould and Hop-Wo 1986; Quinn and teHart 1987). In Johnstone S t r a i t , "hotspots" reported by fishermen and tes t f i s h i n g locations used by the Department of Fisheries and Oceans are along the Vancouver Island shore, along the Hanson Island shore, off Cracroft Point and i n Blackney Pass (Cooke and Groot, i n press; Gould and Hop-Wo 1986). Ultra-sonic tagging of salmon reveals (Quinn and teHart 1987) that migrating salmon encountering headlands, entrances to bays or intersections of channels, become temporarily disoriented, possibly because of confusing current flows r e s u l t i n g from tides and wind d e f l e c t i o n i n these areas. Consequently, salmon tend to aggregate i n these places for a time u n t i l they reorient themselves and move on. Around King Island, k i l l e r whales t r a v e l l e d over much greater distances than when i n Johnstone S t r a i t during summer. This difference i n d a i l y movement between the two areas may be i n response to densities and dispersal of salmon. Near King Island, whales may have needed to cover more area to locate salmon than when i n Johnstone S t r a i t where salmon can number i n the mi l l i o n s (see Table IV). Similar seasonal changes i n t r a v e l distances have been reported for other mammals and have been linked to food abundance and d i s t r i b u t i o n (African wild dogs, Frame et a l . 1979; baboons, Devore and H a l l 1965). From late f a l l to spring, salmon are fewer inshore than during summer, mainly small numbers of coho (Aro and Shepard 1967) and chinook (Aro and Shepard 1967; Healey 1983) salmon and they are more widely dispersed. I suggest that outside of summer months, resident k i l l e r whales regularly cover more area and spend less time i n any one area i n response to t h i s change i n salmon densities and d i p s e r a l . So far, I have i l l u s t r a t e d that 1) the occurrence of northern resident whales i n both Johnstone S t r a i t and King Island i s seasonal, 2) weekly numbers of whales and salmon i n Johnstone S t r a i t during summer are p o s i t i v e l y related, and 3) observations of resident k i l l e r whales indicate that they do prey on salmon i n Johnstone S t r a i t . Together, these re s u l t s support the hypothesis that k i l l e r whales use t h e i r habitat seasonally to take advantage of varying a v a i l a b i l i t y of salmon. My study, however, also revealed that there are differences i n the frequency of occurrence of each northern resident pod i n Johnstone S t r a i t , leading to the hypothesis that within the northern resident community, each pod has i t s own unique home range and pattern of home range use. I w i l l refer to pods as the s o c i a l unit maintaining home ranges, because my analyses were at the pod l e v e l rather than the subpod l e v e l , however, the hypothesis I w i l l now develop could apply equally well to subpods. 46 4) Pod Home Ranges My study has shown that only part of the northern resident community v i s i t s Johnstone S t r a i t frequently during summer and that the occurrence i n Johnstone S t r a i t of less than 50% of the whales in the community i s p o s i t i v e l y associated with salmon abundance there. This raises the question as to, why do so many northern resident k i l l e r whales spend so l i t t l e time i n Johnstone S t r a i t during summer when numerically there would seem to be enough salmon between July and October to feed the entire community? I propose that the reason for the r e l a t i v e l y low numbers of whales in Johnstone S t r a i t during summer may i n part be that t h e i r presence a f f e c t s the actual a v a i l a b i l i t y of t h e i r prey. Though salmon are abundant i n Johnstone S t r a i t , they may be wary of foraging k i l l e r whales and become harder to catch once k i l l e r whales have been present for a time. Certainly, fishermen state that salmon, p a r t i c u l a r l y chinook salmon, respond strongly to the presence of k i l l e r whales and can be d i f f i c u l t to catch for some hours a f t e r whales have passed through (J. Ford unpubl.). This e f f e c t of predators on t h e i r prey, known as resource depression, can be as important or more important than the abundance of prey in determining the movements and foraging decisions of a predator (Charnov et a l . 1976). Consequently, k i l l e r whale pods may need to d i s t r i b u t e themselves i n such a way as to avoid excessive overlap i n any one area i f they are to forage e f f i c i e n t l y . The various c o r o l l a r i e s (bold-type) of my home range hypothesis follow. 47 A pod's seasonal home range consis ts of a several feeding locat ions where salmon are abundant during the same per iod and a pod trave l s among these areas. This i s supported by my observation that even among pods whose occurrence was p o s i t i v e l y associated with salmon abundance i n Johnstone S t r a i t , most, s t i l l spent the majority of summer elsewhere (F ig . 9) . In studies of primates (Goodall 1977; Oates 1987), i t has been argued that systematic u t i l i z a t i o n of the home range leads to more e f f i c i e n t resource exploitation because animals know the abundance and d i s t r i b u t i o n of food within t h e i r range. Thi s may also be true for k i l l e r whales. Heimlich-Boran 1s (1986) study of southern resident whales provides additional support for t h i s c o r o l l a r y . He showed that southern resident whales t r a v e l among areas, and that t h e i r occurrence i n many areas correlates with salmon abundance. Pod home ranges overlap and many feeding locat ions are used simultaneously by more than one pod. This i s c l e a r l y supported by the observation that d i f f e r e n t pods v i s i t e d Johnstone S t r a i t at the same time and that a number of pods were observed together near King Island. Although home ranges overlap s p a t i a l l y there may be temporal separation i n some cases. For example, Gl pod spent very l i t t l e time i n Johnstone S t r a i t during summer and yet t h e i r occurrence was p o s i t i v e l y associated with chum salmon which peak i n f a l l . This suggests temporal p a r t i t i o n i n g (Schoener 1974) of the salmon resource i n some areas. Sightings and acoustic data from the f a l l suggest that Gl 48 and perhaps G12 pods are more common during the f a l l than during the summer. This pattern has been noted by other researchers for a number of years (D. Bain pers. comm.; J . Ford pers. comm.; P. Spong pers. comm). I t i s also possible that Gl pod whales prefer chum salmon. Certainly, dietary differences among groups of mammals which have s i m i l a r food resources i n t h e i r respective home ranges have been reported (chimpanzees, Goodall 1986). However, because sockeye, pink and chum salmon each have d i f f e r e n t migration timings through Johnstone S t r a i t , i t i s d i f f i c u l t to separate differences i n timing of use from prey preference. Seasonal feeding locat ions are v i s i t e d annually by the same pods which have developed preferences for feeding i n these s p e c i f i c areas. This i s supported by the observation that each summer i t i s the same pods that are frequent v i s i t o r s to Johnstone S t r a i t . T r a d i t i o n a l use of certai n areas could develop because of the advantage of feeding i n areas where individuals of the pod have acquired knowledge over many years about l o c a l salmon d i s t r i b u t i o n . Salmon d i s t r i b u t i o n i s affected by current, subsurface topography, temperature and s a l i n i t y (Cooke and Groot, i n press; ; Madison et a l . 1972; Quinn and teHart 1987; Stasko et a l . 1973). Furthermore, d i f f e r e n t species (Argue 1964) swim at d i f f e r e n t depths and d i f f e r e n t stocks of the same species use d i f f e r e n t migration routes (Cooke and Groot i n press). K i l l e r whales are long-lived animals and the stable kin associations within pods mean that experience could be e a s i l y maintained i n 49 the pod and transferred between generations. The advantage of f a m i l i a r i t y from past experience of seasonal food a v a i l a b i l i t y are evident i n home range use by groups of mountain g o r i l l a ( G o r i l l a g o r i l l a berinqei ). In one study (Goodall 1977) , g o r i l l a s anticipated the seasonal growth of bamboo and t r a v e l l e d to s p e c i f i c areas to dig for the young shoots before they had emerged from the s o i l . In another study (Fossey and Harcourt 1977), observations suggested younger g o r i l l a s learned from the experience of older indiv i d u a l s i n the group where to f i n d food and i n p a r t i c u l a r , where to f i n d the best food. The summer home ranges of over h a l f of the northern resident community include feeding areas distant from Johnstone S t r a i t . This i s supported 1) by the observation that pods whose occurrence i n Johnstone S t r a i t was not s i g n i f i c a n t l y associated with salmon abundance were infrequent v i s i t o r s to the S t r a i t and 2) by a small number of incidental summer sightings of northern resident k i l l e r whales (KWSD) away from Johnstone S t r a i t , most of which, have been of pods which spend less than 15% of summer days in Johnstone S t r a i t . These sightings are mainly from coastal areas north of Vancouver Island and from the west coast of Vancouver Island. 3) salmon are abundant i n many areas besides Johnstone S t r a i t between July and October. In p a r t i c u l a r , the salmon which migrate through Johnstone S t r a i t must f i r s t pass through Queen Charlotte S t r a i t . This area, l i k e Johnstone S t r a i t , i s an important commercial f i s h i n g area (Cooke and Groot, i n 50 press). Rivers and Smith Inlets, on the mainland north of Vancouver Island, are also important sockeye f i s h i n g areas where peak weekly numbers of sockeye during mid July can range from 150,000 to 1,000,000 (1984 to 1988) (Aro and Shepard 1967; Goruk and Thomson 1988). Other important f i s h i n g areas for sockeye, pink and chum salmon exi s t throughout many coastal areas northward from Rivers and Smith Inlets to include the Skeena and Nass Rivers near the B r i t i s h Columbia - Alaska border. Commercial catches i n these coastal areas are made between l a t e June and the end of August (Aro and Shepard 1967). On the west coast of Vancouver Island, small runs of salmon are present from June to October (Aro and Shepard 1967; P a c i f i c Region Salmon Resource Management Plan 1988 Vol. H). I predict that resident k i l l e r whales w i l l be found to exploit salmon i n many of these areas. Resident k i l l e r whales pods not only co-occur i n ce r t a i n areas and therefore have overlapping home ranges, but also show neither aggression nor avoidance when encountering other resident pods. In a survey of primate s o c i e t i e s , Cheney (1987) concluded that, i n general, the more overlap that existed among home ranges, the less l i k e l y were aggressive encounters, and i f they did occur, i t was over a s p e c i f i c food item. In another survey, Mitani and Rodman (1979) reported that ranges too large to be p a t r o l l e d d a i l y were undefended. In resident k i l l e r whales, the lack of either aggression towards other pods or avoidance of pods suggests 1) that home ranges are very large and 2) prey are not i n short supply, at least not during the spring 51 and summer when I observed them. A t h i r d p o s s i b i l i t y , however, i s that t h e i r reproductive behaviour may influence t h e i r movements. My observations of k i l l e r whales i n Johnstone S t r a i t were that when d i f f e r e n t pods encounter each other, they tended to t r a v e l together intermingling and engaging i n s o c i a l a c t i v i t y without any signs of aggression. Social contact may be important among pods for breeding opportunities because individuals do not disperse from t h e i r pod, and breeding i s believed to occur between rather than within pods (M. Bigg pers. comm.). For these reasons, i t would seem that pods need to seek out other pods for mating, i f not for other s o c i a l requirements. This may account for some of the overlap among home ranges of resident k i l l e r whale pods, and p a r t i c u l a r l y for the occurrence of infrequent pods i n Johnstone S t r a i t during summer whose presence was not s i g n i f i c a n t l y related to salmon abundance. Although v i r t u a l l y nothing i s known about the mating system of k i l l e r whales, i t i s known that calves are born throughout the year, with b i r t h peaks in f a l l and winter (Bigg 1982). Therefore, because breeding occurs year round, locating potential mates would be expected to influence pod movements year round. CONCLUSION Northern resident k i l l e r whales use t h e i r habitat seasonally to take advantage of seasonally abundant salmon upon which they feed. My res u l t s have also led me to hypothesize that each northern resident k i l l e r whale pod has i t s own unique home range. Home ranges overlap and some feeding areas may be used simultaneously by a number of pods or consecutively by pods. Pods tr a v e l among t h e i r preferred areas, to forage, monitor prey resources and perhaps to locate mates from other pods. Although these c o r o l l a r i e s are supported by my re s u l t s , more observation and detailed study of northern resident k i l l e r whales throughout t h e i r range are now needed to test my hypothesis. 53 LITERATURE CITED Altmann J . 1974. Observational study of behaviour: sampling methods Behaviour. 49: 227-267. Argue A.W. 1964. A study of factors a f f e c t i n g e x p l o i t a t i o n of P a c i f i c salmon i n the canadaian gauntlet fishery of Juan de Fuca S t r a i t . Vol. 1. B.Sc. thesis, University of B r i t i s h Columbia, Vancouver, B.C. 160 pp. Aro K.V. & Shepard M.P. 1967. Salmon of the North P a c i f i c Ocean, part IV spawning populations of North P a c i f i c salmon. Int. North Pac. Fish. Comm. B u l l . 23. Balcomb K.C. I l l , , Boran J.R. and Heimlich S.L. 1982. K i l l e r whales i n Greater Puget Sound. Int. Whaling. Comm. Rep. 32: 681-685 Bigg M.A. 1982. An assessment of k i l l e r whale (Orcinus orca) stocks off Vancouver Island, B r i t i s h Columbia. Int. Whaling Comm. Rep. 32: 655-666. Bigg M.A. Olesiuk P.F., E l l i s G.M., Ford J.K.B. and Balcomb III K.C. 1990a. Social organization and genealogy of resident k i l l e r whales (Orcinus orca) i n the coastal waters of B r i t i s h Columbia and Washington State. In  Press. Int. Whaling Comm. Rep. Bigg M.A., E l l i s G.M., J.K.B. Ford and Balcomb K.C. 1990b. Feeding habits of resident and transient k i l l e r whales in B r i t i s h Columbia and Washington State. Abstr. Third International Orca Symposium, V i c t o r i a , B.C. March 1990. Bigg M.A., E l l i s G.M., Ford J.K.B. and Balcomb K.C. 1987. K i l l e r whales: a study of t h e i r i d e n t i f i c a t i o n , geneology and natural history i n B r i t i s h Columbia and Washington State. Phantom Press & Publishers Inc., Nanaimo, B.C. 54 Briggs D.A. 1988. Usage of the rubbing beaches at Robson Bight Ecological Reserve by whales and boats. Prepared for: Ecological Reserves Program, Parks and Outdoor Recreation Div i s i o n Ministry of Environment and Parks, V i c t o r i a , B.C. 66 pp. Brown J.L. 1966. The evolution of d i v e r s i t y i n avian t e r r i t o r i a l systems. Wilson B u l l . 76: 160-169. Charnov E.L., Orians G.H. and Hyatt K. 1976. Ecological implications of resource depression. Am. Nat. I l l : 247-259. Cheney D.L. 1987. Interactions and relationships between groups. In Primate Societies. Edited by B.B. Smut, D.L. Cheney, R.M. Seyfarth, R.W. Wrangham and T.T. Struhsaker. University of Chicago Press. Chicago. Condy P.R. van Aarde R.J. and Bester M.N. 1978. The seasonal occurrence of k i l l e r whales (Orcinus orca) at Marion Island. J. Zool. (Lond.) 184: 449-464. Cooke K.D. and Groot C. In Press. Homeward migration routes of Fraser River sockeye salmon through B r i t i s h Columbia coastal waters. Can. Tech. Rep. of Fish. Aquat. S c i . Dahlheim M.E. 1981. A review of the biology and exploitation of the k i l l e r whale, Orcinus orca with comments on recent sightings i n Antarctica. Int. Whal. Comm. Rep. 31: 541-546. Devore I. and Hall K.R.L. 1965. Baboon ecology. In Primate behaviour: F i e l d Studies of Monkeys and Apes. Edited by I. Devore. Rinehart & Winston, New York. Evans P.G.H. 1988. K i l l e r whales (Orcinus orca) i n B r i t i s h and I r i s h Waters. R i t F i s k i d e i l d a r . Journal of the Marine Research I n s t i t u t e . Reykjavik. Vol XI: 43-53. Ford J.K.B. 1988. Acoustic behaviour of resident k i l l e r whales (Orcinus orca) off Vancouver Island, B r i t i s h Columbia. Can. J. Zool. 67: 727-745. 55 Ford J.K.B. 1987. A catalogue of underwater c a l l s produced by k i l l e r whales (Orcinus orca) i n B r i t i s h Columbia. Can. Data Rep. Fish. Aquat. S c i . No. 633. Ford J.K.B. and Fisher H.D. 1982. K i l l e r whale (Orcinus orca) d i a l e c t s as an indicator of stocks i n B r i t i s h Columbia. Int. Whal. Commn. Rep. 32: 671-679. Frame L.H. Malcolm J.R. Frame G.W. and van Lawick H. 1979. Social organization of af r i c a n wild dogs (Lycaon pictus) on the Serengeti Plains, Tanzania 1967-1978. Z. Tierpsychol. 50: 225-249. Fossey D. and Harcourt A. H. 1977. Feeding ecology of free -ranging mountain g o r i l l a ( G o r i l l a g o r i l l a b e r i ngei ). In Primate Ecology: Studies of feeding and ranging behaviour i n lemurs, monkeys and apes. Edited by T.H. Clutton-Brock. Academic Press. London pp. 415- 447. Goodall A. G. 1977. Feeding and ranging behaviour of a mountain g o r i l l a group ( G o r i l l a g o r i l l a beringei) i n the Tshibinda-Kahuzi Region (Zaire). In Primate Ecology: Studies of feeding and ranging behaviour i n lemurs, monkeys and apes. Edited by T.H. Clutton-Brock. Academic Press London pp. 450-479. Goodall J . 1986. The chimpanzees of Gombe: patterns of behaviour. Belknap Press of Harvard University Press, Cambridge, pp. 263-266. Goruk R.D. and Thomson B.L. 1988. Rivers Inlet echo sounding program 1967-1988. Can. Man. Rep. Fish. Aquat. S c i . No. 1989. Gould A. P. and Hop-Wo L. 1986. Johnstone S t r a i t chum t e s t f i s h i n g data for 1965-1984. Can. Data. Rep. Fish. Aquat. S c i . No. 522. Gould A.P. and Stefanson A.P. 1985. F i e l d examination of Nimpkish River sockeye timing and migration pathways i n 1981 and 1982. Can. Man. Rep. of Fish. Aquat. S c i . No. 1797. 56 Gould A.P., Stefanson A.P. and Hop-Wo L. 1988. The 1978, 1980, 1982 and 1984 returns of even year pink salmon stocks to the Johnstone S t r a i t study area. Can. Tech. Rep. Fish. Aquat. S c i . No. 1629. Groot C. and Quinn T.P. 1987. Homing migration of sockeye salmon, Oncorhynchus nerka to the Fraser River. Fish. B u l l . 85: 455-469. Guinet C. 1990a. Sympatrie des deux categories d'orques dans l e d e t r o i t de Johnstone, Colombie Britannique. Rev. Ecol. 45: 25-34. Guinet C. 1990b. Behavioural ecology of k i l l e r whales o f f Crozet Archipelago ( 46.26'S, 51.52'E), a comparison with other l o c a l i t i e s . Abstr. Third International Orca Symposium, V i c t o r i a , B.C. March 1990. Guinet C. 1986. Etudie de deux population sympatriques d'orques l e long cotes de Columbie Britannique. Unpubl. 93 p. Healey M.C. 1983. Coastwide d i s t r i b u t i o n and ocean migration patterns of stream- and ocean-type chinook salmon, Oncorhynchus tshawytscha. Can. Field-Nat. 97: 427-433. Heimlich-Boran J.R. 1988. Behavioural ecology of k i l l e r whales (Orcinus orca) i n the P a c i f i c Northwest. Can. J . Zool. 66: 565-578. Heimlich-Boran J.R. 1986. Fishery correlations with the occurrence of k i l l e r whales i n greater Puget Sound. In Behavioural biology of k i l l e r whales. Edited by B. Kirkevold, J.S. Lockard. Alan R. L i s s Inc. New York, pp. 113-131. Hilborn R. and Starr P. 1988. Reconstruction of harvest rates and stock contribution in gauntlet salmon f i s h e r i e s : applications to B r i t i s h Columbia and Washington sockeye (Oncorhynchus nerka). Can. J. Fish. Aquat. S c i . 45: 2216-2229. Hoyt E. 1984. Orca: the whale c a l l e d k i l l e r . Camden House Publishing Inc. Ontario, p. 213. 57 Irvine B.A., Scott M.D., Wells R.S. and Kaufmann J.H. 1981. Movements and a c t i v i t i e s of the A t l a n t i c bottlenose dolphin, Tursiops truncatus, near Sarasota Bay, Fl o r i d a . Fish. B u l l . 79: 671-688. Jacobsen J.K. 1986. The behaviour of Orcinus orca i n the Johnstone S t r a i t , B r i t i s h Columbia. In Behavioural biology of k i l l e r whales. Edited by B. Kirkevold, J.S. Lockard. Alan R. L i s s Inc. New York, pp 135-185. Jonsgard A. and Lyshoel P.B. 1970. A contribution to the knowledge of the biology of k i l l e r whales (Orcinus orca). Nor. J . Zool. 18: 41-48. Kruuk H. 1975. Functional aspects of s o c i a l hunting by carnivores. In Function and Evolution i n Behaviour. Edited  by G. Baerends, C. Beer and A. Manning. Clarendon Press, Oxford, pp. 119-141. Leatherwood S. and Reeves R.R. 1983. The s i e r r a club handbook of whales and dolphins. Sierra Club Books, San Francisco. Lopez J.C. and Lopez D. 1985. K i l l e r whales (Orcinus orca) of Patagonia, and t h e i r behaviour of intentional stranding while hunting nearshore. J. Mammal. 66: 181-183 Lowry L.F., Nelson R.R. and Frost K.J. 1987. Observations of k i l l e r whales, Orcinus orca, i n western Alaska: sightings, strandings and predation on other marine mammals. Can. Field-Nat. 101: 6-12. Macdonald D.W. 1983. The ecology of carnivore s o c i a l behaviour. Nature. 301: 379-384. Madison J.R., Ho r r a l l R.M. Stasko A.B. and Hasler A.D. 1972. Migratory movements of adult sockeye salmon (Oncorhynchus nerka) i n coastal B r i t i s h Columbia as revealed by u l t r a s o n i c tracking. J . Fish. Res. Brd. Canada. 29: 1025-1033. 58 Mitani J.C. and Rodman P.S. 1979. T e r r i t o r i a l i t y : the r e l a t i o n of ranging patterns and home range si z e to defendability among primate species. Behav. Ecol. Sociobiol. 5: 241-251. Oates J.F. 1987. Food d i s t r i b u t i o n and foraging behaviour. In Primate Societies. Edited by B.B. Smut, D.L. Cheney, R.M. Seyfarth, R.W. Wrangham and T.T. Struhsaker. University of Chicago Press. Chicago, pp. 197-2 09. Osborne R.W. 1986. A behavioural budget of Puget Sound k i l l e r whales. In Behavioural biology of k i l l e r whales. Edited by B. Kirkevold, J.S. Lockard. Alan R. L i s s Inc. New York. pp. 211-249. P a c i f i c region salmon resource management plan 1988 Vol. H. West coast of Vancouver Island p 130. Packer C. and Ruttan L. 1988. The evolution of cooperative hunting. Am. Nat. 132: 159-198. Quinn T.P. and teHart B.A. 1987. Movements of adult sockeye salmon (Oncorhynchus nerka) i n B r i t i s h Columbia coastal waters i n r e l a t i o n to temperature and s a l i n i t y s t r a t i f i c a t i o n : u l t r a s o n i c telemetry r e s u l t s . In Sockeye salmon (Oncorhynchus nerka) population biology and future management. Edited by H.D. Margolis and C.C. Wood. Can. Spec. Publ. Fish. Aquat. S c i . 96: 61-77. Rice D.W. 1968. Stomach contents and feeding behaviour of k i l l e r whales i n the eastern north P a c i f i c . Nor. Hvalfangst-Tid. 57: 35-38. Schoener T.W. 1974. Resource p a r t i t i o n i n g i n eco l o g i c a l communities. Science. 185: 27-38. Sergeant D.E., Fisher H.D. 1957. The smaller cetaceans of eastern Canadian waters. J. Fish. Res. Brd. Canada. 14: 83-115. 59 Sigurjonsson J.T., Lyrholm T., Leatherwood S., Jonsson E. and Vikingsson G. 1988. Photoidentification of k i l l e r whales Orcinus orca o f f Iceland 1981 through 1986. R i t F i s k i d e i l d a r . Journal of the Marine Research I n s t i t u t e . Reykjavik. Vol XI: 100-114. S i n c l a i r . A.R.E. 1983. The function of distance movements i n vertebrates. In The ecology of animal movements. Edited  by I.R. Swingland, P.J. Greenwood. Clarendon Press Oxford, pp. 241-259. Spong P. and Symonds H. 1990. Patterns and trends i n the occurrence of Orcinus orca i n the Johnstone S t r a i t area. Abstr. Third International Orca Symposium. V i c t o r i a , B.C. March 1990 Spong P., Bradford J. and White D. 1970. F i e l d studies of the behaviour of k i l l e r whales Orcinus orca. Proc. 7th Annu. Conf. B i o l . Sonar Diving Mamm. 7: 169-174. Stasko A.B., H o r r a l l A.D. and Stasko D. 1973. Coastal movements of mature Fraser River pink salmon (Oncorhynchus crorbuscha) as revealed by ultrasonic tracking. J . Fish. Res. Brd. Canada. 30: 1309-1316. Vo i s i n J.F. 1972. Notes on the behaviour of the k i l l e r whales (Orcinus Orca L.) Nor. J. Zool. 20: 93-96. Wilkinson L. Systat: The system of s t a t i s t i c s , Evanston 111.: Systat Inc. 1988. Wursig B. 1986. Delphinid foraging strategies In: Dolphin cognition and behaviour: a comparative approach. Edited  by R. S. Shusterman, J. Thomas and F. G. Wood. Lawrence Erlbaum Associates Inc. New Jersey, pp. 347-359. Zar J.H. 1984. B i o s t a t i s t i c a l analysis. Prentice-Hall, Englewood, New Jersey. 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
https://iiif.library.ubc.ca/presentation/dsp.831.1-0098406/manifest

Comment

Related Items