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The use of synthetic predator odours to elicit an avoidance response in the roof rat (Rattus rattus) Burwash, Michael David 1996

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T H E U S E OF S Y N T H E T I C P R E D A T O R O D O U R S T O E L I C I T A N A V O I D A N C E R E S P O N S E I N T H E R O O F R A T (Rattus rattus) by Michael David Burwash B.Sc. , The University of British Columbia, 1989 A T H E S I S S U B M I T T E D I N P A R T I A L F U L F I L L M E N T OF T H E R E Q U I R E M E N T S F O R T H E D E G R E E OF M A S T E R O F S C I E N C E in T H E F A C U L T Y O F G R A D U A T E S T U D I E S (Department of Forest Sciences) We accept this thesis as conforming to the required standard T H E U N I V E R S I T Y OF B R I T I S H C O L U M B I A October, 1996 © Michael D . Burwash, 1996 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 r o € - f c " S T <S>CA€mcE:S> The University of British Columbia Vancouver, Canada Date M O \ i S~ /^h DE-6 (2/88) A B S T R A C T I evaluated mongoose (Herpestes auropunctatus) feces and eight synthetic predator odours for eliciting avoidance responses and/or reduced feeding by captured wild roof rats (Rattus rattus). I released individual rats into an open box stainless steel arena, partitioned in half by a wall with an opening allowing passage from one side to the other, as well as access to a covered "safe area". Each half of the arena contained a bowl with a chunk of coconut and a vial of either water or one of the predator odours. I used a video camera to record: 1) time until each rat entered the arena, 2) time elapsed until first eating bout, 3) time spent in each half of the arena, 4) number of eating bouts and 5) consumption. Although there were no statistical differences in any one variable, rats displayed trends in response to the predator odours in terms of increased elapsed time before initial arena entry and initial eating bout, a lower number of eating bouts and less food consumption, than in the respective control groups. The odour which produced the greatest differences in response relative to the control group was D M D I T (red fox (Vulpes vulpes) feces, mustelid anal scent gland). Field trials were conducted to determine whether the synthetic predator odours 3,3-dimethyl-l,2-dithiolane (DMDIT) and £,Z-2,4,5-trimethyl-A 3 -thiazoline (TMT) were effective at eliciting a behavioural response in wild roof rats (Rattus rattus). The study site was a macadamia nut orchard with a recent history of roof rat feeding damage. The synthetic predator odours were encapsulated in urethane devices which could then be secured to tree branches. Radio telemetry and mark-recapture were used to assess behavioural responses to the predator odours. Mark-recapture data assessed capture numbers, mean male body weight, median distance moved and proportion of capture locations relative to treatment areas. Radio telemetry provided data on home range size (minimum convex polygon), median distance from center of activity and proportion of readings in treated areas. Results from the field trials indicated no treatment effects between pre- and post-treatment weeks or between treatments. Insight was also gained as to the movement patterns of roof rats within an orchard environment. ii T A B L E O F C O N T E N T S A B S T R A C T i i T A B L E O F C O N T E N T S i i i LIST OF T A B L E S v LIST O F F I G U R E S iv A C K N O W L E D G E M E N T S ix C H A P T E R 1. L A B O R A T O R Y E V A L U A T I O N O F P R E D A T O R O D O U R S F O R E L I C I T I N G A N A V O I D A N C E R E S P O N S E I N R O O F R A T S I N T R O D U C T I O N 1 M E T H O D S 4 Capture and Maintenance 4 Assignment to Treatment Groups 5 Arena Design 5 Test Procedure 8 Predator Odours 9 Statistical Analysis 11 R E S U L T S 12 Summary of Trends in Results. 20 DISCUSSION : 22 C H A P T E R 2. F I E L D T E S T I N G S Y N T H E T I C P R E D A T O R O D O U R S F O R E L I C I T I N G A N A V O I D A N C E R E S P O N S E I N R O O F R A T S I N T R O D U C T I O N 27 M E T H O D S 30 Study Site 31 Mark-Recapture 32 Radio Telemetry 35 Predator Odour Semiochemicals... 36 Experimental Design 37 Analysis 39 R E S U L T S 42 Mark-recapture 42 Trappability: 42 Capture Numbers: 42 Breeding: 45 Body Weight: 45 Mean Maximum Distance Moved ( M M D M ) : 47 Capture locations relative to treatment areas: 47 Telemetry 51 S E S S I O N 1 Median Convex Polygon (MCP) home range: 52 Median Distance from Center of Activity (MDIS): 52 Proportion of telemetry locations in treated trees: 57 S E S S I O N 2 Median Convex Polygon (MCP) home range: 57 Median Distance from Center of Activity (MDIS): 57 Proportion of telemetry locations in treated trees: 65 DISCUSSION 70 S U M M A R Y 75 R E F E R E N C E S 78 iv L I S T O F T A B L E S Table 1.1 Scientific chemical name, abbreviation and source of predator odours tested in laboratory evaluation (abbreviation used throughout rest of document) 10 Table 1.2 Variables measured and analysis technique utilized to evaluate laboratory testing of predator odours 12 Table 1.3 Summary of trends in roof rat response to treatments relative to the control group response (based on P values and descriptive results of Figures 1.2-1.7) 21 Table 2.1 Estimates of Jolly trappability for roof rats in Control, D M D I T and T M T treatment grids (3 samples/mean) in Session 1. Values are mean percent trappability (average (number caught/Jolly-Seber population estimate) x 100%, Krebs and Boonstra 1984) with 95% confidence intervals in parentheses 44 Table 2.2 Mean male body weight (grams) of roof rats captured on Control, D M D I T and T M T treatment grids in Session 1. Values are mean weights with standard error (SE) and sample size (n) 47 Table 2.3 Mean maximum distance moved ( M M D M ) between consecutive trapping weeks of roof rats captured on Control, D M D I T and T M T treatment grids in Session 1. M M D M is measured (meters) between first-capture-point in each of two successive trapping weeks. Values are in meters with standard error (SE) and sample size (n) 49 v L I S T O F F I G U R E S Figure 1.1 Laboratory testing arena design for evaluation of predator odours to elicit an avoidance response in the roof rat (not to scale) 7 Figure 1.2 Mean time elapsed (seconds) to initial arena entry for each of nine odour treatment groups. Data is displayed with sex grouped. Each value is the mean ± standard error (SE) 13 Figure 1.3 Mean time elapsed (minutes) to first observed eating bout for each of nine odour treatment groups. Data is displayed with sex grouped. Each value is the mean ± standard error (SE) 14 Figure 1.4 Mean time spent (minutes) in arena (over 60 minutes) for each of nine odour treatment groups. Data displayed with sex and sides grouped. Each value is the mean ±standard error (SE) 16 Figure 1.5 Mean total number of eating bouts observed (over 60 minutes) for each of nine odour treatment groups. Data displayed with sex and side grouped. Each value is the mean ± standard error (SE) 17 Figure 1.6 Mean male consumption (grams) for each of nine odour treatment groups. Data is displayed by side (treatment/control). Each valued is the mean ±standard error (SE) 18 Figure 1.7 Mean female consumption (grams) for each of nine odour treatment groups. Data is displayed by side (treatment/control). Each valued is the mean ± standard error (SE) 19 Figure 2.1 Location of study grids within the macadamia orchard blocks. Displays relative location of study grids and odour treatment applied during Session 1 and Session 2 Treatment 1 (not to scale) 33 Figure 2.2 Total number of roof rat captures and recaptures (numbers/300 trap nights) over five trapping weeks in Session 1 of the field study. Odour treatment period indicated by vertical hatched lines and horizontal arrow. Data is displayed by study grid 43 Figure 2.3 Total number of individual male roof rats captured (numbers/300 trap nights) by age (all adults captured in breeding condition) in Session 1 mark-recapture trials. Treatment period indicated by vertical hatched bars and horizontal arrow 46 vi Figure 2.4 Proportion of roof rat captures in traps within or adjacent (within 1 tree) to treated areas. Data is from Session 1 mark-recapture and displayed by treatment type (denned in legend) by week. Treatment period indicated by vertical hatched lines and arrow 50 Figure 2.5 Min imum convex polygon ( M C P ) home range estimates (m2) for individual roof rats located during Session 1 (June 15, 1994 - August 31, 1994). Treatment applications indicated by downward arrows 53 Figure 2.6 Mean minimum convex polygon ( M C P ) estimates (m2) for three treatments (Control, D M D I T and T M T ) by telemetry week during Session 1 (June 15, 1994 -August 31, 1994). Each value is the mean of at least three replicates ± standard error (SE) 54 Figure 2.7 Median distance travelled from center of activity (MDIS) estimates (m) for individual roof rats located during Session 1 (June 15, 1994 - August 31, 1994). Treatment applications indicated by downward arrows 55 Figure 2.8 Mean median distance travelled from center of activity (MDIS) estimates (m) for three treatments (Control, D M D I T and T M T ) by telemetry week during Session 1 (June 15, 1994 - August 31, 1994). Each value is the mean of at least three replicates ± standard error (SE).... 56 Figure 2.9 Proportion of telemetry locations in treated trees for individual roof rats in Session 1 (June 15, 1994 - August 31, 1994). Treatment applications indicated by downward arrows 58 Figure 2.10 Mean proportion of telemetry readings in treated trees for three treatments (Control, D M D I T and T M T ) by telemetry week during Session 1 (June 15, 1994 -August 31, 1994). Each value is the mean of at least three replicates ± standard error (SE) 59 Figure 2.11 Min imum convex polygon ( M C P ) home range estimates (m2) for individual roof rats located during Session 2 (September 20, 1994 - December 10, 1994). Treatment applications indicated by downward arrows 60 Figure 2.12 Mean minimum convex polygon ( M C P ) estimates (m2) for three treatments (Control, D M D I T and T M T ) by telemetry week during Session 2 Treatment 1 (September 20, 1994 - November 4, 1994). Each value is the mean of at least seven replicates ± standard error (SE) 61 vii Figure 2.13 Mean minimum convex polygon (MCP) estimates (m2) for three treatments (Control, D M D r T and T M T ) by telemetry week during Session 2 Treatment 2 (November 9,1994 - December 10, 1994). Each value is the mean of at least seven replicates ± standard error (SE) 62 Figure 2.14 Median distance travelled from center of activity (MDIS) estimates (m) for individual roof rats located during Session 2 (September 20, 1994 - December 10, 1994). Treatment applications indicated by downward arrows 63 Figure 2.15 Mean median distance travelled from center of activity (MDIS) estimates (m) for three treatments (Control, D M D I T and T M T ) by telemetry week during Session 2 Treatment 1 (September 20, 1994 - November 4, 1994). Each value is the mean of at least seven replicates ± standard error (SE) 64 Figure 2.16 Mean median distance travelled from center of activity (MDIS) estimates (m) for three treatments (Control, D M D I T and T M T ) by telemetry week during Session 2 Treatment 2 (November 9, 1994 - December 10, 1994). Each value is the mean of at least seven replicates ± standard error (SE) 66 Figure 2.17 Proportion of telemetry locations in treated trees for individual roof rats in Session 2 (September 20, 1994 - December 10, 1994). Treatment applications indicated by downward arrows 67 Figure 2.18 Mean proportion of telemetry readings in treated trees for three treatments (Control, D M D I T and T M T ) by telemetry week during Session 2 Treatment 1 (September 20, 1994 - November 4, 1994). Each value is the mean of at least three replicates ± standard error (SE) 68 Figure 2.19 Mean proportion of telemetry readings in treated trees for three treatments (Control, D M D I T and T M T ) by telemetry week during Session 2 Treatment 2 (November 9, 1994 - December 10, 1994). Each value is the mean of at least three replicates ± standard error (SE) 69 viii A C K N O W L E D G E M E N T S I would like to thank my supervisor, Dr. Tom Sullivan, for his guidance and encouragement as well as providing me with the opportunity to conduct applied wildlife research. I would also like to thank Dr. Mark E . Tobin for his support and academic input. This research was funded through an N S E R C operating grant to Dr. Sullivan and by the Denver Wildlife Research Center (DWRC) of the United States Department of Agriculture. The entire staff at the D W R C Hilo field station provided endless support and encouragement: Robert Sugihara, Ann Koehler, Rodney Mederias and Lillian Kamigaki. I am grateful to Kau Agribusiness Company, Inc. for allowing me to conduct the field study in their orchard. M y field assistants Doreen Manly and Christine Cheng were tireless and indispensable. I would also like to thank my committee members, Drs. Staffan Lindgren and Mike Feller, for their advice throughout my studies and on earlier drafts, as well as statistical advice from Rick Engeman and Dr. V . LeMay. I am also indebted to my colleagues for their comments and motivation: Markus Merkens, Bruce Runciman, Doug Ransome, Barry Booth, Christine Cheng, Vanessa Craig and Pontus Lindgren. Finally I would like to thank Sarah Stelter for her endless support and encouragement throughout my research. ix C H A P T E R 1 L A B O R A T O R Y E V A L U A T I O N O F P R E D A T O R O D O U R S F O R E L I C I T I N G A N A V O I D A N C E R E S P O N S E I N R O O F R A T S I N T R O D U C T I O N The Macadarnia nut (Macadamia integrifolia), being a desirable food item internationally, is a crop of high commercial value. In the 1993-94 crop year, Hawaiian growers produced 22 million kg (wet in-shell weight) of macadamia nuts with a statewide farm value of $33 million (Hawaiian Agricultural Statistics Service 1992). Crop damage by rodents has been a problem on the Hawaiian Islands for many years and annual losses have been estimated at $3-4 million (Tobin et al. 1993). The roof rat (Rattus rattus) has been identified as the primary pest species in Macadamia nut orchards, with the Polynesian rat (R. exulans) also present, but not considered as a serious damage agent (Tobin 1992). Various management techniques have been applied but none has proven effective. Current rodent control techniques in Hawaii involve methods of poisoning (rodenticides) and/or the use of kill-traps. Studies on the effectiveness of common rodenticides have shown many poisons to be too selective for certain rat species (Tobin 1992). This argument is related to increased zinc phosphide use, and is believed to explain the increase in Norway rat (Rattus norvegicus) populations relative to the roof and Polynesian rat (Rattus exulans) in sugarcane fields (Tobin et al. 1990). Another basic problem with zinc phosphide is bait shyness resulting from sublethal consumption of the bait. A s macadamia growers need to protect their crop over an extended period of time, this learned bait avoidance becomes a problem. Timing of application in the orchard is important, and restrictions regarding the use of zinc phosphide prior to harvest are 1 currently required; primarily to reduce crop residues and primary/secondary accidental poisoning of humans. The potential effects on other non-target animals (e.g. feral pigs, avian predators) and possible transmission through the food web are also of concern with anticoagulant rodenticides (Engeman and Pank 1984). The use of synthetic predator semiochemicals in wildlife management is a growing area of research. Although pheromones have been used extensively in agricultural pest management, the focus has been primarily on invertebrate communities. The application of predator odours as a management tool at the small mammal level has been recently investigated. Sullivan et al. (1988a, 1988b, 1988c) have shown suppressed damage and/or an avoidance response in synthetic predator odour experiments with various small mammal populations in both agricultural and forested ecosystems. Significant results have been observed in the following North American species: an avoidance response in snowshoe hare (Lepus americanus) in coniferous seedling plantations, suppressed feeding by montane and meadow voles (Microtus montanus and M. pennsylvanicus) in apple tree orchards, and an avoidance response by northern pocket gophers (Thomomys talpoides) in apple tree orchards. The encouraging results from the previously described odour response studies, combined with an extensive rodent problem on the Hawaiian islands, provide an ideal situation in which to explore potential management applications. Based on the previous study efforts, including a recent field study in Hawaii which also indicated that rats avoid traps scented with mongoose feces (Herpestes auropunctatus) (Tobin et al. 1995), I proposed to examine the possibility of using synthetic predator odours to prevent rodent feeding damage in a macadamia nut orchard. This biological control (biorational) method attempts to prevent rodent damage through a behavioral response to a predator odour. Although most of the odours to be tested were not that of 2 established predator on the Hawaiian Islands, I predicted that a fear/avoidance response should be innate. Volatiles from red fox (Vulpes vulpes) fecal droppings elicited a fear response in Wistar lab rats which had not been in contact with predators for generations (Vernet-Maury et al. 1984). Boag and Mlotkiewicz (1994) found decreased rabbit numbers in areas treated with a complex multicomponent synthetic repellent derived from lion feces. Self-anointing behaviour with weasel (Mustela sibirica) anal scent gland secretion, considered a defensive response, was displayed by juvenile rice-field rats (Rattus rattoides) which had been lab reared (Xu et al. 1996). I based my predictions of roof rat response to predator odours on such previous studies involving small mammals. Vernet-Maury et al. (1984) assessed fear response observations in an open-field arena which considered time of emergence, exploratory movements, grooming, urination and defecation. Other studies have tested predator odour avoidance through reduced consumption by small mammals (Calder and Gorman 1991; Epple et al. 1993; Heale and Vanderwolf 1994). I also discussed potential behavioural observations with Dr. R. J. Blanchard (pers. comm.) of the Psychology Department at the University of Hawaii at Manoa. Based on the success of previous small mammal field studies and the apparent innate responses by small herbivores to carnivore odours, I predict that roof rat behaviour can be manipulated with synthetic odours, and potentially lead to crop protection. This study was designed to test the following hypotheses. The presence of a predator odour wi l l : H I : increase the time elapsed before an individual first enters the arena and before its first eating bout for the treatment groups relative to the control group. 3 H2: reduce the amount of time spent on the treated side and reduce the total time spent on both sides of the arena; H3: reduce the number of eating bouts on the treated side; H4: reduce the amount of food consumed on the treated side; relative to the control groups. M E T H O D S The open-box arena design allowed a large viewing area to observe an individual rat's response. A video camera (JVC BY-1000) situated above the arena recorded the information and eliminated observer bias. As a management interest was to reduce feeding damage, consumption became one of the response variables measured. Other quantitative variables measured were: time to first entry, time to first eating bout, time spent in arena and number of eating bouts. Separating the open box arena into two identical halves allowed a predator odour to be tested against a control. Capture and Maintenance of Animals R o o f rats were live trapped in the Waikaea Forest Reserve on the island of Hawaii, and maintained in animal rooms at the United States Department of Agriculture (USDA) /Animal and Plant Health Inspection Service (APHIS)/Animal Damage Control (ADC)/Denver Wildlife Research Center ( D W R C ) field station in Hi lo . Only adult animals were maintained for testing 4 which was determined by sexual maturity and weight (>90 g). Over 120 roof rats were initially captured, from which 100 animals (50 of each sex) were randomly selected to meet the study design requirements of 100 animals. Test animals were housed in individually numbered cages and were provided with water and laboratory chow ad libitum prior to testing. The animals were maintained on a 12 hour light/12 hour dark schedule with the room temperature ranging from 20° to 22° C. Mongooses (Herpestes auropunctatus), maintained to collect fresh fecal samples, were captured in gulch regions near the city of Hi lo and were also housed at the D W R C Hi lo Field Station. Two adult mongooses, one of each sex, were maintained in an outdoor wire pen and provided with shelter, bedding, water ad libitum, and fed one rat per day. Assignment to Treatment Groups The 100 test rats were assigned to 10 treatment groups using a randomization program which ranked each sex group by weight before randomly assigning treatments. Following the treatment assignment, each test group consisted of five males and five females. As the odour trials were divided into two phases, each treatment group was further divided into two sub-groups (2 males/3 females or 3 males/2 females). The test animals were then housed according to treatment group and sub-group (A or B) . 5 Arena Design The size of the arena was maximized according to the largest field of view allowable with the video camera lens. The arena measured 150 cm long by 60 cm wide and 120 cm in height (Fig. 1.1). A middle wall divided the box into two equal areas with a small opening (15 cm X 15 cm) located in the bottom corner to allow access between both sides of the arena. The side of the arena with the opening in the middle wall also had the only opening to outside the arena, a 10 cm X 10 cm opening with an outer sliding door. Brackets were secured on either side of the door to permit the animal transfer cage to be directly attached to the arena. Once the animal transfer cage was attached, the sliding door could be opened to allow the test animal access to the arena. As the odours tested were very volatile, materials to construct the arena were chosen based on their properties of low absorption and ease of cleaning. The arena walls, door, and animal transfer cage were constructed of stainless steel. The arena had no bottom and was set on a sheet of white Formica. Following any animal trial, the arena was cleaned with a combination of bleach/detergent/water, then rinsed with water and sprayed with ethanol to evaporate any residual odours. The arena and camera were located in a separate room from the animal housing room, where temperature, lighting, and air circulation could be controlled. The video camera was situated on a tripod directly above the middle of the arena. A television located outside of the testing room was used for live viewing. During video recording, a low-intensity red-filtered light simulated nocturnal conditions under which the animals are normally active. 6 150 cm u o CD t ) ht = 120cm (^J note: middle wall has a 15 cm X 15 cm opening at the bottom corner animal transfer cage -Q_) - food dish m - odor placement top view ' sliding door (up) covering 10 cm X 10 cm opening to arena 60 cm opening in middle wall: 15 cm X 15 cm E o o CM opening to arena: 10 cm X 10 cm Figure 1.1 Laboratory testing arena design for evaluation of predator odours to elicit an avoidance response in the roof rat (not to scale). 7 Test Procedure Following pilot trials with non-test animals, it was decided to test and record individuals over a 60-min period. Only one predator odour was tested per day to reduce possible residual odour effects. This design allowed one odour and five individuals to be tested per day during the 12-hr dark phase (1800-0600H) when the animals are normally more active. The procedure was divided into two phases encompassing ten days each. Each phase was identical in procedure and order of odour compounds tested. This schedule was chosen to try and prevent any effect that may occur with time, as individuals tested in the final trials will have been housed for three weeks longer than those tested initially. The phases were also scheduled as closely together as possible to further reduce any time effects. Each test animal was pre-exposed to the arena on the two days prior to the test day. This procedure decreased any novel effect the arena environment may have had on the individual. The pre-exposure trials were 15 min in duration and were also recorded on video tape. The only differences that the pre-exposure trials had from the odour trials were a shorter duration, an absence of odour compounds, no prior food deprivation and they were performed during the latter quarter of the 12-hr light period. Prior to the day of odour testing, animals were food-deprived for 24 hrs to increase their motivation to feed. This is a common procedure in laboratory trials investigating rodent behavioural responses (R.J. Blanchard pers. comm.). For the odour testing, 10 /uL of a given compound was pipetted into a urethane vial, with the odour released through a small hole in the cap of the vial. The only exception to this procedure was for the mongoose feces treatment, in which ~ 1 g was placed directly into the vial with two 8 drops of water (-0.02 mL). The odour vial was attached to the outside of a bowl which contained a measured quantity of coconut bait. The bowls were then placed in the corners of the arena, against the wall opposite from the animal transfer cage (Fig. 1.1). Each trial had one vial containing the test chemical and the other containing water. For each treatment group, the placement of the test odour was randomly located for the first sub-group and placed on the opposite side for the second sub-group. This assignment reduced any bias for either side. On the test day, the individual was moved from the animal room to the test room with the animal transfer cage. The individual was left undisturbed for four minutes to allow the subject to rest following the transfer procedure. The duration of 'rest' time was determined based on discussions with Dr. R. J. Blanchard (pers.comm.) and time constraints. Using the television the observer would record information while the animal was being video-taped, while further data were recorded during subsequent review of the tapes. Each test animal was recorded for 60 min after opening the sliding-door. After each trial, the animal was transferred back to the animal housing room, and the arena dismantled for cleaning. The coconut bait would be checked for signs of feeding and re-weighed to measure consumption during the trial. Predator Odours Chemical compounds to be tested as repellents were originally derived from predator species; commonly from the anal scent gland, urine, or feces. The compounds have generally been identified either from extracts of these secretions or from the volatiles that emanate from them. The components believed to have semiochemical activity were then prepared synthetically. A l l of the odour constituents (semiochemicals) tested were synthetic liquids except for mongoose feces which 9 were collected from freshly voided material. The semiochemical compounds were synthesized at >90% purity by A . D . Woolhouse, Industrial Research Limited, New Zealand and Phero Tech Inc., Delta, B . C . , Canada. A list of the odours, an abbreviation and their original source are given in Table 1.1. Table 1.1 Scientific chemical name, abbreviation and source of predator odours tested in laboratory evaluation (abbreviation used throughout rest of document). Chemical Name Abbrevia t ion Source 2,2-dimethylthietane D M T - mustelid (Mustela spp.) anal scent gland 3,3-dimethyl-1,2-dithiolane D M D I T - mustelid (Mustela spp.) anal scent gland - red fox feces isopentenyl methyl sulphide IPMS - red fox urine Herpestes auropunctatus feces M O N G - mongoose feces 4-mercapto-4-methylpentan-2-one M M P - red fox urine & feces (±)-3-propyl-1,2-dithiolane P D T - stoat (Mustela erminea) anal scent gland (±)-2-propylthietane PT - stoat (Mustela erminea) anal scent gland S B T - mouse aggressor 2-sec-butyl-A2-thiazoline hormone £,Z-2,4,5-trimefhyl-A 3 - thiazoline T M T - red fox feces 10 Statistical Analysis The results were analyzed as a fixed effect randomized block design with sex being a blocked factor. Blocking sex was performed as previous laboratory studies with the roof rat found differences between male and female consumption (Sugihara et al. 1985). For the variables which took into account the 'side' factor, a 3-factor repeated measures analysis of variance ( A N O V A ) was used with sex and treatment as the two non-repeated factors. Variables which did not use side as a factor were analyzed with a 2-factor analysis of variance (sex and treatment). See Table 1.2 for the details regarding the specific analysis for the variables measured. The univariate repeated measures analysis has similar assumptions to the regular A N O V A , however, this analysis also assumes circularity among the levels of within-subject factor (Scheiner and Gurevitch 1993). The within-subject factor in this case is 'side', and as there are only two levels of this factor, I assumed that the difference between these two factors equaled the same value for each treatment level. This is based on the graphical representation of the descriptive statistics 'by side'. A s the sequence of treatment levels is random and we assume no carry-over effects on the variables measured from one treatment to the next, the circularity assumption is probably met (Scheiner and Gurevitch 1993). The 'time spent' variable was analyzed as 2-factor non-repeated A N O V A as the temporal nature of the data would violate an assumption in the repeated measures analysis. As the time a subject spends on one side is inversely related to the time it spends on the opposite side, the 'side' data becomes less independent (R. Engeman pers. comm.). The level of significance («) was set at the 0.05 level for all analyses of variance. A l l statistical analysis was performed using the statistical program S A S (SAS Institute 1988). 11 Table 1.2 Variables measured and analysis technique utilized to evaluate laboratory testing of predator odours. Var iab le Analysis M e t h o d time to emerge 2-factor A N O V A time to first eating bout 2-factor A N O V A time spent in arena - total 2-factor A N O V A number of eating bouts 3-factor repeated measures A N O V A consumption 3-factor repeated measures A N O V A R E S U L T S Although overall differences were not detected at «=0.05 (P=0.13) for time elapsed to arena entry, the data was graphed with sexes grouped to assess trends (Fig. 1.2). The mean entry times of rats exposed to D M D I T (97 sec, SE=23 sec) and I P M S (93 sec, SE=27 sec) were marginally greater than that for rats in the control group (39 sec, SE=16 sec). For time elapsed to first eating bout, no significant difference was detected between treatment groups (P=0.19). Again the data was graphed to assess potential trends (Fig. 1.3). The mean elapsed time to first eating bout for rats exposed to D M D I T (20.6 min, SE=7.2 min), M M P (19.3 minutes, SE=7.4 min), M O N G (15.7 min, SE=7.1 min), PT (15.1 min, SE=6.4), S B T (17.3 min, 6.2 min) and T M T (21.1 min, SE=6.8 min) were greater than that for rats in the control group (6.2 min, SE=2.5 min). These six treatment groups were also the only treatments with animals that did not eat throughout the odour trial. 12 140 120 w n o o o CD U) CL CD 100 80 60 CD CD E 40 20 Mean and SE 4 CONT DMDIT DMT IPMS MMP MONG PDT Treatment Group (n=10) PT SBT TMT Figure 1.2 Mean time elapsed (seconds) to initial arena entry for each of nine odour treatment groups. Data is displayed with sex grouped. Each value is the mean ± standard error (SE). 13 30 25 to CD 20 a> 15 CO Q_ a CD CD E 10 • Mean and SE CONT DMDIT DMT IPMS MMP MONG PDT Treatment Group (n=10) PT SBT TMT Figure 1.3 Mean time elapsed (minutes) to first observed eating bout for each of nine odour treatment groups. Data is displayed with sex grouped. Each value is the mean ± standard error (SE). 14 There were no statistically significant differences (P=0.16) found with respect to the time spent variable by side or by treatment. A s there were no side or sex differences for the total time spent, the data were sex and side grouped for the graphical display in Figure 1.4. This would describe the amount of time spent in the arena as opposed to within the covered transfer cage. There are observable trends in the amount of time spent in the arena between treatment groups and the control. The mean time spent in the arena for rats exposed to D M D I T (20.0 min, SE=3.4), D M T (22.4 min, SE= 3.0), M M P (25.4 min, SE=5.0) and M O N G (22.8 min, SE=4.2) were lower than that for control group rats (36.2 min, SE=3.1). For the observed number of eating bouts there was a significant overall treatment effect (Fig. 1.5). Duncan's multiple comparison test indicated that rats exposed to D M D I T or T M T had fewer (P=0.05) eating bouts than rats exposed to either IPMS or PDT. Neither results were different from rats in the control group. A s there were no sex or side differences, this information was grouped by treatment. There were no side or treatment differences in food consumption, however, there was a significant difference in consumption by sex. Overall, mean male consumption was 0.64 g and female consumption was 0.41 g (P=0.03). The data were grouped separately for each sex and displayed in Figure 1.6 and Figure 1.7. 15 40 35 h w £ 30 CD E 25 20 15 Mean and SE • 4 4 • CONT DMDIT DMT IPMS MMP MONG PDT PT SBT TMT Treatment Group (n=10) Figure 1.4 Mean time spent (minutes) in arena (over 60 minutes) for each of nine odour treatment groups. Data displayed with sex and sides grouped. Each value is the mean ± standard error (SE). 16 10 o .o CD CD CD . Q E • • • Mean and SE A CONT DMDIT DMT IPMS MMP MONG PDT PT SBT TMT Treatment Group (n=10) Figure 1.5 Mean total number of eating bouts observed (over 60 minutes) for each of nine odour treatment groups. Data displayed with sex and side grouped. Each value is the mean ± standard error (SE). 17 3.5 3 | 2.5 £0 Q. E 1.5 CO c ° 1 o 1 Mean and I D 0.5 CONT DMDIT DMT IPMS MMP MONG PDT Treatment Group (n=10) PT SBT TMT Figure 1.6 Mean male consumption (grams) for each of nine odour treatment groups. Data is displayed by side (treatment/control). Each valued is the mean ± standard error (SE). 18 2.5 Mean and SE C O E 2 S 1.5 c g "5. i 1 CO c o O 0.5 CONT DMDIT DMT IPMS MMP MONG PDT Treatment Group (n=10) PT SBT TMT Figure 1.7 Mean female consumption (grams) for each of nine odour treatment groups. Data is displayed by side (treatment/control). Each valued is the mean ± standard error (SE). 19 Summary of Trends in Results Individual variability may have masked any differences due to the odours, and the sample size used was not great enough to identify differences statistically. By comparing the descriptive results summarized in Table 1.3, different trends across the measured variables for particular treatments become apparent. I based these trends on the probability values from statistical testing as well as the graphical representation of the results (Figs. 1.2 to 1.7). From this, I was able to decide which odours produced the greatest potential behavioural avoidance response. I concluded that D M D I T , T M T , M M P and M O N G treatments had the most inhibitory effect on the behaviour of the roof rats. 20 Table 1.3 Summary of trends in roof rat response to treatments relative to the control group response (based on P values and descriptive results of Figs. 1.2-1.7). (X=difference; +=slight difference; - = similar results) Odour: D D I M M P P S T M M P M O D T B M D T M P N T T T I S G Observation: T Increased Time to First Entry X + X - + -(P=0.13) Increased Time to First Eating Bout X - - X + - + X X (P=0.16) Less Time Spent in Arena X X + X X + X + + (P=0.16) Lower Number of Eating Bouts X - - - - - - - X (P=0.05, no differences from control) Lower Consumption - Males - - - X - - - - X (P=0.03, sex difference) Lower Consumption - Females (P=0.03, sex difference) 21 D I S C U S S I O N The intent of the laboratory study was to detect behavioural responses to the presence of predator odours. Utilizing the laboratory setting allowed for the control of environmental factors which could contribute to increased experimental error and reduced power to detect a predator odour result. Assessment of an avoidance response was developed based on criteria utilized in previous laboratory odour studies. Many odour studies involving small rodents take place in a controlled laboratory setting, where behavioural responses can be observed directly. Some studies have combined the observed behavioural information with physiological measures such as changes in plasma hormone levels (Vernet-Maury et al. 1984). Other studies have focused on more quantitative responses to odours such as the amount of food consumed. Mountain beaver (Aplodontia rufa) showed reduced consumption from bowls scented with coyote (Canis latrans) urine compared with control bowls (Epple et al. 1993). Avoidance response of pocket gophers (Thomomys talpoides) to weasel (Mustela erminea) scent was determined by number of captures between scented and unscented traps (Sullivan and Crump 1986). Chance and Mead (1955) showed that a greater stimulus change produced greater delays before a lab rat would start eating. Previous laboratory odour studies have attributed fear responses to particular observed behaviours. However, there are often discrepancies in the interpretation of particular behavioural responses, and various researchers have attributed different meanings to similar activities. The observed behaviour of defecation has been identified as a fear response (Vernet-Maury et al. 1984) and also as a non-fear response. Grooming and jumping are also two observations which are difficult to qualify as a stress response. Grooming observed in the presence of predator odours has 22 been described as a defensive response (Xu et al. 1996). Others have considered grooming to occur once the animal considers the surroundings safe (Vernet-Maury et al. 1984). Jumping is a common activity for roof rats and is often considered an exploratory behaviour, especially in novel surroundings. Many of the common behavioural observations such as stretch, sniff and rearing, also appear to be more exploratory in nature and not necessarily indicative of a phobic response. Because of the potential discrepancies in the interpretation of these behaviours, they were not used in this study. However, a common measurement for testing the effectiveness of predator odours, in producing an avoidance response, has been food consumption (Calder and Gorman 1991; Epple et al. 1993; Heale and Vanderwolf 1994). This and other discrete observations were used to conclude whether or not the predator odours tested produced the desired response. As there are a wide range of responses one could potentially observe and interpret, this study focused more on quantitative measurements. There is no preferred standard procedure to test the effect of predator odours, and hence an arena was designed to allow the observation of many likely behaviours. I also wanted to allow the individual a 'safe zone' provided by access to a covered transfer cage. This design provided the individual with cover, food and an exploration area to observe behavioural responses in a two-choice situation. I assumed that i f a particular odour signalled danger to a rat, then it would try and avoid the odour by: delaying entry into odour-treated arena, delay time to first eating bout, spend less time on the treated side, and eating less from the treated side of the arena. This research addressed the following predictive hypotheses: H I : The presence of a predator odour wil l increase the time elapsed before an individual first enters the arena and before its first eating bout for the treatment groups relative to the control group. H2: The presence of a predator odour w i l l reduce the amount of time spent on the treated side relative to the control side, and reduce the total time spent on both sides of the arena. 23 H3: The presence of a predator odour will reduce the number of eating bouts on the treated side relative to the control side. H4: The presence of a predator odour wi l l reduce the amount of food consumed on the treated side relative to the control side. The results from the statistical analysis indicated no difference in the observed responses to predator odour treatments. I feel that much of the potential odour effects may have been hidden by the high individual variability observed in these rats. This variability in roof rats probably increased experimental error and reduced the power of statistical tests to detect significant results. This known variability may provide the rationale for raising « levels to increase the power of the test, while recognizing the elevated potential for Type I errors. Recognition of this issue as well as the near significant statistical results (P~ 0.15, see Table 1.3), suggested further consideration of the data. Rats are considered a generalist species able to adapt readily to changes in the environment. This flexibility is partly due to the high variability in individual behaviour. During the preliminary trials, there were observed differences in the response to the novel arena. Some individuals spent the majority of time in the covered transfer cage, others ventured into the arena very cautiously, while some darted quickly between the two sides and the transfer cage. This variation between individuals has been suggested to explain Rattus species' adaptability (Ewer 1971). Having a broad range of individual behavioural responses allows the population as a whole to adapt readily to changes in the environment. Other differences in responses may have occurred depending upon the type of predator odour tested. Jedrzejewski et al (1993) showed different patterns of behavioural response of bank voles (Clethrionomys glareolus) to seven different predator odours. They found that voles 24 responded differently to various species of carnivores and summarized these differences in a behavioural 'response' table. Vernet Maury et al. (1984) compared responses to predator odours using a behavioural 'score', based on whether the observation was considered that of a 'stress' response or not. This technique allowed the combination of responses to give a final behavioural 'score' with which to compare the odours. I followed a similar approach in combining the different response variables into a 'Summary Table' (Table 1.3) to assist in interpreting the results. The odours of interest were D M D I T , T M T and M M P , all unfamiliar (in recent evolutionary times) synthetic odours as well as M O N G , a predator odour familiar to the roof rat. D M D I T delayed the time spent exploring/searching in the arena, increased the time elapsed to first eating bout, reduced the time spent in the arena, reduced the number of eating bouts and total consumption. M O N G had similar results although the total number of eating bouts was not different from the control group. Other promising odours based on the 'Summary Table' were T M T and M M P . T M T also produced the greatest fear response in previous laboratory studies using rats (Vernet-Maury et al. 1984). This latter study also found that M M P and D M D I T produced a fear response, which support the descriptive trend findings in this study. Although no trials were performed to test for habituation, the results indicate that the roof rat tends to avoid mongoose feces, a familiar predator on most of the Hawaiian islands. The test rats had probably encountered mongoose odour before being captured, and their seemingly avoidance response in the arena suggest that this fecal odour is recognized. This avoidance in the testing arena provides some evidence that the wi ld roof rat has not habituated to mongoose odour and appeared to avoid the odour. These indications of avoidance in the testing arena may also reflect what has been demonstrated in the field as a recent live-trap study found lower roof rat capture success in traps that had previously captured a mongoose (Tobin et al. 1995). 25 Similar trends in avoidance response to that of the mongoose odour was observed with some of the synthetic odours tested. Based on the live-trap study findings of Tobin et al. (1995), it is expected that the synthetic predator odours would produce a similar avoidance response in the field. Although the synthetic odours lack any positive re-enforcement in the field, I believe that an avoidance response will be observed initially. This prediction is supported by studies that indicate rodents have an innate recognition of predator odours. Cattarelli and Chanel (1979) demonstrated the greatest olfactory 'awakening influence' for lab-reared Wistar rats occurred with red fox fecal odour. Vernet Maury and colleagues have also demonstrated a fear response in lab rats when exposed to various predator odour chemicals (Vernet Maury et al. 1984, 1992). Orkney voles (Microtus arvalis) which have not been in contact with predators for generations also displayed an avoidance response when exposed to carnivore odours (Gorman 1984). Whether this is a response to a particular common semiochemical is unknown, but definite behavioural responses have been observed in rodents exposed to various predator odours. The measured responses in the laboratory suggest an avoidance behaviour by the wild Hawaiian roof rat to synthetic predator odours and support efforts to further test the odours in field trials. 26 C H A P T E R 2 F I E L D T E S T I N G S Y N T H E T I C P R E D A T O R O D O U R S F O R E L I C I T I N G A N A V O I D A N C E R E S P O N S E I N R O O F R A T S I N T R O D U C T I O N The roof rat (Rattus rattus) occurs in a wide variety of habitats throughout the state of Hawaii. Its reputation as an adaptable generalist is apparent on this Pacific island by its presence in wooded gulches and forests, agricultural crops and human structures (Tomich 1986). Rattus species have a history of rapid colonization following their initial introduction to many Pacific islands (Atkinson 1985; Buckle and Fenn 1992). Rattus damage to the native flora and fauna as well as to managed food crops and food storage areas has been well documented (Stone 1985; Tomich 1986; Buckle and Fenn 1992; Lund 1994). Besides posing a risk to native fauna through direct consumption (i.e. plants, bird eggs, insects), rodents are also capable of out-competing other animals with similar food sources (Clark 1980). The roof rat has also contributed to the rapid decline in native bird species on the islands, as this is the only rodent species that regularly utilizes tree canopies (Atkinson 1985; C P . Stone pers.comm.). Rodents have also been a host for the transmission of various life-threatening health hazards (Gratz 1992). Bacterial diseases of rodents can be transmissible to humans primarily through bites of infected fleas (Tomich 1986). Currently on the islands of Hawaii , the roof rat is known to carry the bacteria leptospire (Gratz 1992), which produces the disease leptospirosis in mammals. This disease can be a danger to humans as it is transmitted through direct or indirect contact with rodent secretions. To reduce the transmission of this disease, treatment of water sources before consumption is recommended in many areas of Hawaii. 27 There is a valid concern regarding the detrimental effects rodent populations are having on Hawaii's threatened flora and fauna. A n additional concern has been raised by various agricultural growers with regard to rodent feeding damage. Sugarcane, macadamia nut and coffee orchards have been experiencing rodent damage problems for several years in Hawaii (Tomich 1986; Tobin et al. 1990, 1992; Sugihara et al. 1995). Research into methods to control rats has been extensively investigated by the Denver Wildlife Research Center (formerly of the U.S. Fish and Wildlife Service) Hawaii Field Station and the Hawaiian Sugar Planters' Association. Past attempts to control roof rat numbers in site specific areas using toxicants have met with limited success. Current studies are attempting this approach utilizing modified baits and bait stations with livetrap and radio telemetry techniques (S. Fancy pers.comm.). Their capacity to withstand rodenticide poisoning attempts can be attributed to their neophobic nature, physiological resistance, social structure and high reproductive rate allowing rapid reinvasion (Prakash 1988). Other factors contributing to their resiliency in the Hawaiian islands are their ability to breed year round combined with abundant food sources. The use of predator odour semiochemicals for the management of problem wildlife is an area of recent interest. Previous field studies have found predator odours to be effective in the management of various small mammal species (Sullivan et al. 1988a, 1988b, 1988c). These field trials using predator odours were usually preceded by smaller scale studies, such as an arena or pen trial, to initially determine i f the animal of concern would respond. Once a desired response was observed, a field trial would then be suggested or performed. To date, most studies investigating predator odours have focussed on mammals native to North America. The promising results in many of these studies suggest a similar approach may provide a management technique for the roof rat in Hawaii. 28 Laboratory studies have indicated that rodents display a fear response when exposed to synthetic predator odours (Vernet-Maury et al. 1984). The laboratory trials performed prior to this study (see Chapter 1) indicated that the most promising odour for eliciting an avoidance behaviour in the Hawaiian roof rat was D M D I T . T M T and M M P (4-mercapto-4-methylpentan-2-one) also seemed to produce an avoidance response in the laboratory trials, however, T M T was selected for field testing as it was also the odour generating the greatest fear response in Wistar lab rats (Vernet-Maury et al. 1984). Tobin et al. (1996b) used radio telemetry to examine roof rat movement patterns within a macadamia orchard. This work gained insight into the biology of roof rats in orchard environments, deteimining that most of the rats den underground in the porous lava substrate, or build nests from leaf clippings in the tree canopy. Rats in the orchard were found to have a definite nocturnal feeding schedule with the greatest number of animals leaving their den sites by 2300H. Lunar cycles and rainfall did not seem to affect this feeding pattern. Tobin et al. (1995) have also shown that roof rats avoid traps scented with mongoose urine and feces in field trials, suggesting that the potential for odour avoidance exists. Many studies have also gathered useful information on changes in small mammal populations using mark-recapture techniques (Krebs 1966; Ritchie and Sullivan 1989; Sullivan 1990). Research specific to the roof rat has used live-trapping techniques as well as radio telemetry analysis (Chin 1983). The design and sampling methodology used for my study were based on previous mark-recapture studies, and a pilot field trial was also conducted to test the radio transmitter collars and recapture success with various baits. Based on the laboratory results in Chapter 1 and other small mammal field study results, I predict that roof rats w i l l avoid predator odours in the field. 29 This study was designed to test the following hypotheses: H 1 : Predator odour treatments will decrease the number of roof rats captured in treated relative to control (untreated) areas. H2: Population dynamics (breeding and body weights) of roof rats w i l l be lower on treated areas than on control areas. H3: The mean maximum distances moved ( M M D M ) between subsequent capture (mark-recapture) and median distances from center of activity (MDIS) (telemetry) wi l l be greater for roof rats in predator odour treated areas. H4: The home range size of roof rats w i l l increase in the presence of predator odours. H5: The proportion of roof rat locations in treated trees will be lower on treatment areas relative to control areas. M E T H O D S The effectiveness of predator odours at producing a response in the roof rat was determined using mark-recapture and radio telemetry techniques. The field study was conducted in two sessions based on the battery life of the radio transmitters: Session 1 from June to August 1994 and Session 2 from September to December 1994. The radio telemetry procedure remained the same for both sessions, however, the mark-recapture methodology was modified slightly between sessions as discussed' below. 30 Study Site The study site was a 999-ha macadamia nut orchard located 15 k m south of Hi lo in the state of Hawaii . The orchard was on the windward side of the island of Hawaii where rainfall was substantial (>150 mm/yr) and the general topography relatively flat. The majority of the orchard was comprised of ~25-year-old macadamia trees of different varieties. This varietal mix is primarily for pollination purposes. Orchard soils were volcanic with a 0.3 m layer of crushed lava on the surface providing the substrate in which the macadamia trees were planted. The porous nature of the lava beneath this crushed layer provided rats with an extensive tunnel network easily accessible through many openings to the surface. Vegetative ground cover throughout the orchard was rninimal as a result of the regular use of herbicides and manual clearing of leaves. The orchard was laid out in blocks (mostly rectangular) separated by gravel access roads on all sides and Norfolk island pine tree (Araucaria heterophylla) wind-breaks on at least two sides of each block. These windbreak areas had a very deep duff layer composed of fallen debris and orchard trimmings which provided another denning area for rodents. , This orchard was chosen to test the predator odours based on two main factors. First, by the recent history of rodent damage recorded in the macadamia orchard (Tobin et al. 1993), and second, the relative homogeneity of the orchard. This homogeneity provided a large area of very similar blocks in which to replicate treatments. The blocks used for this study were all composed of the same tree variety ratio (variety 660-86%:508-9%:212-5%) which were also of similar age (20-25 years), height (8-10 m) and density (240 trees/ha). Three 20-ha blocks were relatively flat and each block was separated by at least 200 m (Figure 2.1). The three blocks were then divided into six 4-ha grids for the field study. This allowed the study to focus on animals living primarily 31 within the blocks and to avoid those individuals utilizing the windbreaks. Each grid was 4 ha (100 m X 400 m) in area, at least 20 m from the road edge and at least 300 m from the adjacent grid in the same block. As the trees were planted in a grid layout (6.5 m X 6.5 m spacing), specific row and tree locations could be assigned to every tree. This 6-month field study was separated into two periods: Session 1 from June 13, 1994 to August 31, 1994 and Session 2 from September 19, 1994 to December 14, 1994. For both sessions, pre-treatment information was gathered for both the mark-recapture and telemetry information. Mark-recapture Session 1: One hundred live-traps were used on each grid (80 Hagaruma / 20 Tomahawk) with placement on every three to four trees per row on every other row pair within each 4-ha grid. Traps were placed on larger lateral branches between 1 and 2 m above ground as previous five-trapping had greater capture success at this location ( M . E . Tobin pers. comm.). Placing the traps on the ground tended to capture more mongoose, and those which did capture rats on the ground had increased trap deaths as a result of mongoose predation. A l l traps were cleaned prior to use and were secured to the branch using nylon twine and rubber bands. Pre-baiting was carried out 3 days prior to the first trap day of a given trapping week to allow animals to become familiar with taking bait from the traps. This was accomplished by locking open the traps and placing a coconut chunk smeared with peanut butter inside. On the initial trap day, the traps were re-baited and set during the day, left open throughout the night and checked the following morning. Each trapping week was comprised of 3 nights of trapping following pre-baiting with trapping taking place every 3 weeks. 32 I CONTROL 1 (9P) ~m Treatment & replicate # Grid Label Road Norfolk Pine Windbreak Road Orchard Block CONTROL 2 (14H) 160 m" Figure 2.1 Location of study grids within the macadamia orchard blocks. Displays relative location of study grids and odour treatment applied during Session 1 and Session 2 Treatment 1 (not to scale). 33 Checking the traps involved identifying the species, and recording the colour, sex, weight, breeding condition (males: scrotal/abdominal; females: perforate/non-perforate and pregnant/not pregnant) and attaching an individually numbered ear tag for identification. A n open ended mesh net-bag with a rope cinch was used to handle the animal for data collection and ear-tagging. This procedure was done for all rat and mongoose captures. The only mark-recapture data analyzed was that from Session 1 as the design in Session 2 yielded too few captures to provide a worthwhile comparison. As the trappabilities were quite variable on each grid and the duration of trapping limited to 5 weeks in Session 1, open population estimates, using the program Livetrap were applied with caution. Further to this analysis, information on composition of rat populations was gained. This provided some useful insight as to changes within the captured population. Session 2: In this session, the above mark-recapture design was used to first collar the animals, after which the trap layout was modified. Because of the low number of traps in treated areas in the first session, the design was modified to focus trap placement in treated trees for Session 2. Once the areas to receive treatment were determined (see odour placement section), 10 traps were placed within the treated area and trapped on the same schedule and procedure as in Session 1. 34 Radio Telemetry Roof rats were initially captured in live-traps in each of the 6 study grids, using the Session 1 mark-recapture design. Only adult rats were used for telemetry to maintain a similar age class and sufficient sample size. To ensure that radio-collar weight would have minimum effect on normal behaviours, no animals under 90 g were used for radio telemetry. Six animals (3 males and 3 females) were initially radio-collared on each grid. The animals were anesthetized with a general anesthetic, Metofane, by placing the individual into a sealed plastic container lined with anesthetic-treated (-10 mL) cotton. Within 5-10 min the animal would be sedated enough to handle safely. The individual would then be processed as in the mark-recapture procedure, and fitted with a radio transmitter neck collar (Holohil PD-2C). Before releasing the animal, the transmitter signal would be checked and the animal placed back into the trap to recover. Usually 10-15 min following the collaring, the animal would fully recover and be released at the point of capture. As roof rats are primarily nocturnal, most of the telemetry locations were taken during the night. A telemetry week consisted of 4 days of locating animals with each telemetry day comprised of 1 day location (between 1200-1700H) and 3 night locations (1900-2100H; 2101-2300H; 2301-0100H). This design was based on the number of active radio-collars and the number of observers available. A n observer was equipped with a headlamp, a portable radio receiver (Custom Electronics of Urbana Inc. or Wildlife Materials Inc.) and a hand-held yagi antenna (Wildlife Materials Inc.) to locate radio-collared rats. During an individual's location, the animal would be tracked to a single tree with its location either above or below ground determined. The specific information recorded was: observer, date, time, receiver, tuning and signal strength, location (tree/underground/surface), activity (moving/stationary), visual confirmation (yes/no), and general weather conditions (wind, rain, cloud cover, lunar phase). A shortened data label would then be 35 transcribed onto flagging tape and secured to the appropriate tree. A t the end of the 4-day telemetry week the exact location (row and tree label) for each flag was determined and recorded before flag removal. During each telemetry night, the order in which grids were sampled and specific rats tracked was systematically shifted during each 2-hr location period. This would ensure that individual rats were not always being located at the same point within each 2-hr period. Predator Odour Semiochemicals The chemical compounds to be tested as repellents were originally derived from predator species; commonly from the anal scent gland, urine, or feces. The compounds have generally been identified either from extracts of these secretions or from the volatiles that emanate from them. The components believed to have semiochemical activity are then prepared synthetically, albeit as racemates. Lastly, the synthetic odour is encapsulated in a release device (usually P V C or urethane) to control release rates and protect the chemicals from excessive exposure during field use (Sullivan et al. 1990). The synthetic odours were synthesized by A . D . Woolhouse, Industrial Research Limited, New Zealand and Phero Tech Inc., Delta, B . C . , Canada, then encapsulated in release devices by Phero Tech Inc. A list of the odours, an abbreviation and their original source are given in Table 1.1. The D M D I T devices were loaded with 8 mg of active ingredient in a 3-cm urethane device, while T M T devices were loaded with 10 mg of active ingredient in a 6-cm urethane device. The difference in concentration of active ingredient was a result of the amount of synthetic chemical available at the time of the study. A s the release devices had an expected field life of 3 weeks, they were replaced once after the third week following treatment application within each session (6 treatment weeks per session). 36 Experimental Design Assignment of treatments (DMDIT, T M T and control) to the 6 grids was random with two replicates for each treatment. The application of the treatment was focussed in areas specific to individual ariimals rather than in a broadcast area design. This was decided primarily because of the reliable individual movement data available with the telemetry procedure. I was also limited by the number of odour repellents available and personnel to apply the treatment. Focussing on the individual animal allowed assessment of whether individuals shifted their activity in reaction to placement of the semiochemicals. Another advantage to this design was the ability to address general dose-response (by varying treatment levels) and locational questions regarding the treatment application. Following 2 weeks of pre-treatment telemetry locations, specific areas to be treated were determined. Every animal on a grid would receive the same treatment odour even though the treated areas were not continuous over the entire grid but concentrated in specific areas for each animal. This was to prevent any possible contamination of different treatments within a grid. The design in Session 2 was modified following the results from Session 1. Session 1: Treated areas were composed of 9 adjacent trees within an individual's weekly home range area. The frequency of locations during the pre-treatment period was mapped and a 9-tree area was determined by selecting the trees most visited. The general shape of the treated area was a 3-tree by 3-tree square. However, due to missing or dead trees, this shape often varied. To maintain consistency in the treated areas, the treatment trees had to be adjacent to at least one other treated tree. 37 The predator odours were applied by placing a coated wire through a hole in each repellent device and twisting the wire ends to form a loop. Flagging was then used to secure the device to tree branches. Each treated tree received 8 odour devices placed at varying heights (2-4 m) throughout the canopy. Their location was also dispersed relative to the main trunk of the tree. Generally* 4 devices were placed distal to the trunk and 4 were placed proximal, at variable heights above ground. Specific areas were often found where definite feeding activity was occurring. This was indicated by gnawed shells and husks found in flat 'pocket' areas where large branches were leaving the main trunk of the tree. These locations and obvious runway areas (along larger branches), were treated with repellent devices if recognized on the trees receiving treatment. Session 1 treated areas totalled 72 devices/area (per radio-collared rat). The schedule was designed such that telemetry weeks occurred on the first and third week following initial treatment application and following re-application, with mark-recapture taking place in the weeks between telemetry sessions. Session 2: After mapping the results from Session 1, it was apparent that the treatment area was quite small relative to the individual's weekly home range which often led to the rats avoiding the "treated" trees on the control grids (marked but not treated). During Session 2 I expanded the treated area to 16 trees and increased the number of odour devices placed in each tree to 12. A further modification of the application was to place 4 of the 12 devices around the trunk at a height of -0.5 m. The total number of devices per treatment area in this session was increased to 192 devices/area (per radio-collared rat). 38 This session was also divided into two treatment periods: the first period (Session 2 Treatement 1) used the same treatment designation as in Session 1. Following two weeks of post-treatment telemetry the semiochemicals were removed. After a week delay, the second period (Session 2 Treatment 2) was initiated with a pre-treatment telemetry week followed by two weeks of post-treatment monitoring. For the second treatment, semiochemical applications were systematically shifted so that each rat received a different treatment for Session 2 Treatment 2. The design was balanced so that each Treatment 1 group would be divided so that each half would receive different semiochemicals for Treatment 2. The intent was to observe for any trends in individual response to a new semiochemical treatment. Analysis Mark-recapture: Initially, comparisons in the number and composition of the captured individuals were generated. The number of captures were totalled by week and separated into proportion of recaptures for comparison. Population information was calculated using open population estimates with the program Livetrap (Krebs 1991). Statistical comparisons of the population estimates were not generated because trappabilities were quite variable (Table 2.1) (C.J. Krebs pers. comm.). However, comparisons were made with the actual capture information per unit effort and other population parameters using randomization testing ( R A N D M I Z E program) (Manly 1990). Randomization techniques are designed for detecting non-random change in studies with little or no replication of experimental units and for paired time-series data from individual treatment and control systems (Carpenter et al. 1989). This methodology is not bound by the assumptions 39 of parametric statistics (random sampling, normally distributed populations and equal variances) as the technique determines the error distribution of its test statistics by randomly reordering the data set (Carpenter et al. 1989; Manly 1990). Mark-recapture data were also used to compare capture success within specific treated and untreated areas (capture success within/adjacent to treated trees). This information could also be compared to results from radio telemetry techniques. These data were grouped among treatments as a result of the low number of traps within or adjacent to treated areas. The number of recaptures by individual was insufficient to provide a meaningful home range estimate from the mark-recapture data. Where sufficient replication existed, analyses of variance were conducted to compare between treatments by trapping week. Telemetry: I calculated the rninimum area convex polygon (MCP) for each radio-collared rat to estimate its weekly home range size and median distance from center of activity (MDIS) . M D I S was calculated as the median distance of all locations for an animal from its center of activity (mean x and y coordinates of all locations) (SAS Institute Inc. 1988). M C P was calculated with McPaal Micro-computer Programs for the Analysis of Animal Locations (Stuwe and Blohowiak 1989). In order to calculate home range estimates, a minimum of 14 locations was needed based on a pre-study plot of home range size versus number of locations. I also calculated the proportion of telemetry locations in treated trees from the total number of in-tree locations. The capture success relative to treatment areas was determined by considering the proportion of captures in traps located within or adjacent to (defined as within 1 adjacent tree) 40 treated areas. This information should indicate whether an individual is selecting specific trees within its weekly home range. Separate 2-way repeated measures A N O V A s for the telemetry variables were performed to compare between pre- and post-treatment and between treatments. Sex was grouped as previously telemetry work in this orchard found no difference in home range estimates between sexes (Tobin et al. 1996b). A l l A N O V A s were conducted with alpha (<*) set at 0.05. To make multiple comparisons, Duncan's multiple range test was used with an experiment-wise error rate of 0.05 (Saville 1990). 41 R E S U L T S Mark-recapture Total number of captures for a trapping week ranged from 5-55 individuals. The number of captures and recaptures by grid is displayed in Figure 2.2. There was a balanced sex ratio for all populations throughout the study. Trappability: Jolly trappability for male and female roof rats was estimated for each grid for Session 1 (Table 2.1). Trappability of roof rats varied by grid and by sex with very broad 95% confidence intervals. None of the eight pair-wise comparisons were significantly different (based on non-overlapping 95% confidence intervals). There was also no consistent difference between female and male trappability. The generally variable trappability suggested caution be used when interpreting Jolly population estimates. Capture Numbers: Five-hundred-eighty-two individual roof rats were captured a total of 1089 times during 5 weeks of live-trapping. Subdividing these numbers by treatment: 214 roof rats were captured on the control grids, 189 captured on the D M D I T treatment grids and 179 captured on the T M T treatment grids. The low trappability values suggest caution when interpreting Jolly-Seber population estimates, therefore Jolly-Seber population estimates were not used to detect a response to treatment. 42 Control 1 (9P) 50 40 30 20 10 0 INew 3 Recapture Treatment :M •: 60 T3 <D | 50 I 30 I 20 13 £ 10 * 0 H i 1 4 7 10 Trapping Week DMDIT 1 (9H) Treatment < • 15 4 7 10 15 Trapping Week 60 CD ^ 50 8 4 0 20 XI £ 10 60 | 50 c f 4 0 I 30 I 20 = 10 Control 2 (14H) Treatment < • 4 7 10 15 Trapping Week 4 7 10 15 Trapping Week TMT 2 (14P) Treatment < • 4 7 10 15 Trapping Week Figure 2.2 Total number of roof rat captures and recaptures (numbers/300 trap nights) over five trapping weeks in Session 1 of the field study. Odour treatment period indicated by vertical hatched lines and horizontal arrow. Data is displayed by study grid. 43 Table 2.1. Estimates of Jolly trappability for roof rats in Control, D M D I T and T M T treatment grids (3 samples/mean) in Session 1. Values are mean percent trappability (average (number caught/Jolly-Seber population estimate) x 100%, Krebs and Boonstra 1984) with 95% confidence intervals in parentheses. Male Female Control l ( G r i d 9 P ) 31.0 34.3 (-13.9-75.9) (7.8-60.9) 2 (Grid 14H) .75.3 36.7 (2.6-148.0) (5.2-68.1) D M D I T Treatment 1 (Grid 9H) 25.7 7.3 (-11.7-63.0) (-0.7-15.3) 2 (Grid 12H) 50.3 45.3 (4.2-96.5) (35.3-55.4) T M T Treatment 1 (Grid 12P) 59.3 79.3 (-28.7-147.4) (33.8-124.9) 2 ( G r i d l 4 P ) 21.0 46.7 (-0.2-42.2) (-36.1-129.4) 44 The relative capture success information was however tested through randomization testing to compare capture numbers per 300 trap-nights between treatments and between pre- and post-treatment. Randomization testing detected no non-random difference in capture numbers of roof rats in pairwise comparisons of controls and D M D I T treatments (two-tailed, P=0.47), controls and T M T treatments (two-tailed, P=0.47) or D M D I T and T M T treatments (two-tailed, P=0.74). Breeding: The number of males in breeding condition (scrotal=adult) did not change following treatment application (Fig. 2.3). Randomization testing found no non-random difference in number of scrotal males captured for pairwise comparisons of controls and D M D I T treatments (two-tailed, P=0.71), controls and T M T treatments (two-tailed, P=0.20) and D M D I T and T M T treatments (two-tailed, P=0.50). Body Weight: There was no significant difference in the average weight of male roof rats between control and treatment stands during the pre-treatment weeks ( A N O V A , week 1:P = 0.69, week 4:P=0.87), during the treatment period ( A N O V A , week 7:P=0.68, week 10:P=0.48) or during the post-treatment period ( A N O V A , week 15:P=0.46) (Table 2.2). 45 Control 1 (9P) 1 4 7 10 15 Trapping Week Control 2 (14H) 45 C D CL ,« 30 CO I 15 c Treatment ^ 1 4 7 10 15 Trapping Week DMDIT 1 (9H) 45 8 30 CO | 15 T3 Treatment 4 7 10 Trapping Week 15 DMDIT2(12H) 45 | 30 •g '> T3 15 1 Treatment 4 7 10 Trapping Week 15 45 -o CO | 15 C Treatment 1 4 7 10 15 Trapping Week TMT 2 (14P) 45 Q. « 30 O co 3 > c 15 Treatment 4 7 10 15 Trapping Week Figure 2.3 Total number of individual male roof rats captured (numbers/300 trap nights) by age (all adults captured in breeding condition) in Session 1 mark-recapture trials. Treatment period indicated by vertical hatched bars and horizontal arrow. 46 c _o 'co CO p 0 0 to T3 so c 03 P T3 ° -a is e P u a a c3 O cfl cu C 3 _ g & <+H « 0 T3 2 53 t£ to 1 5-1 bfi £ bp ab '53 '53 0 3 CU T3 O • O p - a a c CD & co P =3 S > <N CN <D ^ 1 P B CO O OH o c a g C U O ( U 0 3 * B 8 B & p P i-i B 0 0 P 0 0 p 0 0 p W 0 0 P W oo p CO • c o 2 <* a o U c o o o o o c o CN VO VO VO Ov O t--CN as v o in c o o o m c o VO m VO CO 0 0 r--VO ^ o o v o VO O CN 0 0 m as m as v o r--0 0 o CO CN as as c o i n O ON c o m in r~ as £ 0 0 CN i n r--CN O X CN 0 0 <N 0 0 -^t VO v o as 0 0 CO o o c o m v o o o CN VO in r-ON 0 0 c~- as OH (OH CN 47 Mean Maximum Distance Moved ( M M D M ) : Mean maximum distance moved ( M M D M ) between consecutive trapping weeks are shown in Table 2.3. There were no significant differences in M M D M between treatments during Pre-treatment ( A N O V A , P=0.77), or following treatment application ( A N O V A , week 4-7: P=0.69, week 7-10: P=0.20). Capture locations relative to treatment areas: Proportion of captures in traps within or adjacent to (within 1 adjacent tree) treated areas is displayed in Figure 2.4. Although capture numbers were quite low, the distribution of the captures relative to the treated areas provided an indication of predator odour avoidance. Randomization testing detected no non-random difference in the proportion of captures within/adjacent to treated areas in pairwise comparisons of controls and D M D I T treatments (two-tailed, P=0.11), controls and T M T treatments (two-tailed, P=0.85) or D M D I T and T M T treatments (two-tailed, P=0.07). 48 Table 2.3 Mean maximum distance moved ( M M D M ) between consecutive trapping weeks of roof rats captured on Control, D M D I T and T M T treatment grids in Session 1. M M D M is measured (meters) between first-capture-point in each of two successive trapping weeks. Values are in meters with standard error (SE) and sample size (n). week 1-4 week 4-7 week 7-10 Pre-treatment Treatment Treatment Grids: Mean S E n Mean S E n Mean S E n Control 9P 10.8 4.8 13 23.8 6.5 13 17.4 5.4 12 14H 30.4 5.9 37 25.7 7.1 25 28.9 7.2 9 D M D I T 9H 22.2 4 19 20.9 8 7 4.5 4.5 3 12H 15.6 3.6 18 23.7 4.2 17 28.1 5.6 13 T M T 12P 17.6 3.6 15 20.5 6.1 13 10.3 3.3 13 14P 27.5 4.1 27 6.3 3.1 11 8.3 3.4 12 49 Figure 2.4 Proportion of roof rat captures in traps within or adjacent (within 1 tree) to treated areas. Data is from Session 1 mark-recapture and displayed by treatment type (defined in legend) by week. Treatment period indicated by vertical hatched lines and arrow. 50 Telemetry For all telemetry data, estimates were initially plotted for each animal for the duration of Session 1. As rats displayed a high degree of individual variability in the laboratory arena trials, I felt it worthwhile to first display the results by individual. A consistent problem throughout Session 1 was transmitter slippage or predation. O f the 6 rats initially collared on each grid, 0-3 rats per grid provided data throughout the entire session. Many of the rats radio-collared either had their transmitters recovered on the surface (-25%) (slip or predation), remained stationary underground (-15%) (slip or predation), or their signal was entirely absent (-5%) (transmitter failure or moved from grid >2 km). In one case a female rat on grid 12P (TMT) lost its radio transmitter in the tree canopy 2 weeks after collaring. This was recovered -5 m above the ground in working condition, with no signs of predation. One animal was observed to have died from predation. This female weighed 120 g and was located on grid 12H during the first week following the initial D M D I T treatment application. The animal was first located in the canopy (1900-2100H) but in the subsequent location (2101-2300H) was observed on the surface running erratically. This activity appeared very unusual as rats were rarely observed on the ground in the orchard. In the final reading (2301-0100H) this individual was recovered on the surface missing half its lower body, with obvious signs of feral cat predation as evidenced by tooth puncture marks in the back of the neck and spine. To combine all individuals for each treatment would have yielded a widely varying sample size by week. It would also have been uncertain to use data from individuals not present throughout most of each session as individual biases would not have been consistent across each telemetry week. I therefore decided to calculate average values only for those rats present throughout at least one pre-treatment and one post-treatment (consecutive) telemetry week. In 51 Session 1 the number of rats (sample size) for all telemetry measurements was at least 3, except in pre-treatment week 1 (not used in the analysis). For Session 2, the number of rats (sample size) for all telemetry measurements was at least 7, except in the pre-treatment week. SESSION 1 Median Convex Polygon (MCP) home range: The individual's weekly M C P home range estimates ranged from 63 m 2 to 4,730 m 2 throughout Session 1. Figure 2.5 displays the results for the individual rat M C P home range estimates indicating the high individual variability. The mean M C P home range estimates by telemetry week are displayed in Figure 2.6. A repeated measures analysis of variance found no difference in treatments within or between weeks ( A N O V A ; P=0.61). Median Distance from Center of Activity (MDIS): Median distance from center of activity (MDIS) for individual roof rats ranged between 4-45 m (Fig. 2.7). The mean MDIS estimates by telemetry week are displayed in Figure 2.8. A repeated measures analysis of variance found no difference in treatments within or between weeks ( A N O V A ; P=0.45). 52 • 163-M 285-F A 408-F e 524-M P1 P3 T1 T3 T4 T6 T7 Week T1 T3 T4 Week T7-• 137-F 385-F A 449-F Grid 9H (DMDIT) 8000 DMDIT DMDIT • 130-F 375-M A 441-F P1 P3 T1 T3 T4 T6 T7 Week T1 T3 T4 Week • 232-F 306-M A 362-F e 485-M Grid 12P(TMT)| • 388-M 460-M P1 P3 T1 T3 T4 T6 T7 Week T1 T3 T4 Week • 182-M ^ 296-M A 356-F Figure 2.5 Minimum convex polygon (MCP) home range estimates (m2) for individual roof rats located during Session 1 (June 15, 1994 - August 31, 1994). Treatment applications indicated by downward arrows. (Legend: symbol for individual, transmitter number - sex) 53 4 0 0 0 r 3 0 0 0 2 0 0 0 1 0 0 0 C O N T R O L DMDIT T M T C O N T R O L DMDIT TMT Pre- t reatment week 3 Treatment week 1 C O N T R O L DMDIT TMT Treatment week 3 4 0 0 0 r C O N T R O L DMDIT T M T Treatment week 4 C O N T R O L DMDIT T M T Treatment week 6 C O N T R O L DMDIT T M T Treatment week 7 Figure 2.6 Mean minimum convex polygon ( M C P ) estimates (m2) for three treatments (Control, D M D I T and T M T ) by telemetry week during Session 1 (June 15, 1994 -August 31, 1994). Each value is the mean of at least three replicates ± standard error (SE). (Legend: symbol for individual, transmitter number - sex) 54 Grid 9P (Control) | • 163-M -O 285-F A 408-F e 524-M Grid 14H (Control) 45 30 15 Control P1 P3 T1 T3 T4 T6 T7 Week • 137-F 385-F A 449-F Grid 9H (DMDIT) 45 30 15 DMDIT I DMDIT 1 A-1 ffl—— i m . . - - " ® ' " -• 130-F 375-M A 441-F P1 P3 T1 T3 T4 T6 T7 Week Grid 12P(TMT)| • 388-M -O 460-M P1 P3 T1 T3 T4 T6 T7 Week Grid 12H (DMDIT) 45 30 15 DMDIT I DMDIT I - \ u P1 P3 T1 T3 T4 T6 T7 Week Grid 14P(TMTJ1| P1 P3 T1 T3 T4 T6 T7 Week • 232-F 306-M A- 362-F e 485-M • 182-M -0- 296-M A 356-F Figure 2.7 Median distance travelled from center of activity (MDIS) estimates (m) for individual roof rats located during Session 1 (June 15, 1994 - August 31, 1994). Treatment applications indicated by downward arrows. (Legend: symbol for individual, transmitter number - sex) 55 4 0 3 0 h 2 0 10 C O N T R O L DMDIT T M T Pre - t rea tment week 3 C O N T R O L DMDIT T M T Treatment week 1 C O N T R O L DMDIT T M T Trea tmen t week 3 4 0 r 3 0 \-C O N T R O L DMDIT T M T Trea tment week 4 C O N T R O L DMDIT T M T Trea tment week 6 C O N T R O L DMDIT T M T T rea tmen t week 7 Figure 2.8 Mean median distance travelled from center of activity (MDIS) estimates (m) for three treatments (Control, D M D I T and T M T ) by telemetry week during Session 1 (June 15, 1994 - August 31, 1994). Each value is the mean of at least three replicates ± standard error (SE). (Legend: symbol for individual, transmitter number - sex) 56 Proportion of telemetry readings in treated trees: Again, these data were initially plotted by individual (Fig. 2.9) with proportion of telemetry readings in treated trees values ranging between 0-85%. Mean estimates for proportion of telemetry locations in treated trees are displayed in Figure 2.10. Repeated measures analysis of variance found no difference in treatments within or between weeks ( A N O V A ; P=0.35). S E S S I O N 2 Median Convex Polygon (MCP) home range: The individual's weekly minimum convex polygon (MCP) home range estimate ranged from 125 m 2 to 12,162 m 2 throughout Session 2 (Fig. 2.11). The mean M C P home range estimates for roof rats in Session 2 Treatment 1 are displayed in Figure 2.12. Repeated measures analysis of variance found no difference in treatments within or between weeks ( A N O V A ; P=0.54). Mean M C P home range estimates for roof rats in Session 2 Treatment 2 are displayed in Figure 2.13. Repeated measures analysis of variance found no difference in treatments within or between weeks ( A N O V A ; P=0.08). Median Distance from Center of Activity (MDIS): Individual data are displayed in Figure 2.14 with median distance from center of activity (MDIS) ranging between 5-60 m No trends in groups of individuals were obvious from these data. Mean M D I S values for roof rats present throughout Session 2 Treatment 1 ranged from 16-26 m (Fig. 2.15). No differences within or between treatment weeks were determined (P=0.34). 57 • 163-M 285-F A 408-F -B- 524-M | Grid 14H (Control) | 1 0.8 I 0.6 o Q. e 0.4 a. 0.2 0 Control Control 1 • \ A T3 T4 Week 0 137-F ^ - 385-F A- 449-F • 130-F 375-M -A- 441-F T1 T3 T4 Week • 232-F -e- 306-M A - 362-F •B- 485-M H 388-M -0- 460-M T1 T3 T4 Week m 182-M •O- 296-M A- 356-F B - 424-F Figure 2.9 Proportion of telemetry locations in treated trees for individual roof rats in Session 1 (June 15, 1994 - August 31, 1994). Treatment applications indicated by downward arrows. (Legend: symbol for individual, transmitter number - sex) 58 0.8 r 0.7 -0,6 - I 0,5 -0.4 - \ ~ \ ~ \ 0.3 - -'-i—5—i T I 0.2 - 1 0.1 - 1 I 1 I o.o I 1 1 1 1 1 1 1 1 I I 1 1 L _ L J 1 1 1 1 C O N T R O L DMDIT T M T C O N T R O L DMDIT T M T C O N T R O L DMDIT T M T P r e - t r e a t m e n t week 3 T rea tmen t week 1 T rea tmen t w e e k 3 C O N T R O L DMDIT T M T T rea tmen t week 4 C O N T R O L DMDIT T M T T rea tmen t w e e k 6 C O N T R O L DMDIT T M T T rea tmen t w e e k 7 Figure 2.10 Mean proportion of telemetry readings in treated trees for three treatments (Control, D M D I T and T M T ) by telemetry week during Session 1 (June 15, 1994 - August 31, 1994). Each value is the mean of at least three replicates ± standard error (SE). (Legend: symbol for individual, transmitter number - sex) 59 6000 4000 2000 m 155-M A 194-F A 550-M S 646-F ^ 726-F P1 P3 T5 T7 P8 T10 T12 Week 6000 4000 2000 P1 P3 T5 T7 P8 T10 T12 Week m 214-M • 583-F A 660-M S 783-F O 821-F -A 910-M P1 P3 T5 T7 P8 T10 T12 Week 6000 4000 2000 P1 P3 T5 T7 P8 T10 T12 Week • 337-M 674-M A 775-M e 854-F • 264-F • 574-F A 615-M e 683-F ^ 961-F Grid 14H| 6000 Control DMDIT B 255-F • 474-M A 596-F S 664-F -e- 795-F A - 881-F P1 P3 T5 T7 P8 T10 T12 Week 6000 4000 2000 • 326-M • 564-M A- 624-M e 759-F -O- 841-F A 921-F P1 P3 T5 T7 P8 T10 T12 Week Figure 2.11 Minimum convex polygon (MCP) home range estimates (m2) for individual roof rats located during Session 2 (September 20, 1994 - December 10, 1994). Treatment applications indicated by downward arrows. (Legend: symbol for individual, transmitter number - sex) 60 4 0 0 0 3 0 0 0 2 0 0 0 1000 C O N T R O L DMDIT TMT Pre-treatment week 1 C O N T R O L DMDIT TMT Pre-treatment week 3 4 0 0 0 r 3 0 0 0 2 0 0 0 1000 h C O N T R O L DMDIT TMT Treatment week 1 C O N T R O L DMDIT TMT Treatment week 3 Figure 2.12 Mean minimum convex polygon (MCP) estimates (m2) for three treatments (Control, D M D I T and T M T ) by telemetry week during Session 2 Treatment 1 (September 20, 1994 - November 4, 1994). Each value is the mean of at least seven replicates ± standard error (SE). (Legend: symbol for individual, transmitter number - sex) 61 4 0 0 0 3 0 0 0 2 0 0 0 1000 I I I I I I C O N T R O L DMDIT TMT Pre-treatment week 8 C O N T R O L DMDIT TMT Treatment week 10 C O N T R O L DMDIT TMT Treatment week 12 Figure 2.13 Mean rninimum convex polygon (MCP) estimates (m2) for three treatments (Control, D M D I T and T M T ) by telemetry week during Session 2 Treatment 2 (November 9, 1994 - December 10, 1994). Each value is the mean of at least seven replicates ± standard error (SE). (Legend: symbol for individual, transmitter number - sex) 62 • 155-M • 194-F A 550-M S 646-F 726-F T4 T6 P8 T10 T12 Week T4 T6 P8 Week T10 T12 Grid 12H 70 60 '_ DMDIT Control • 214-M 50 • 583-F 40 A 660-M 30 S 783-F 20 821-F 10 "'A -A- 910-M 0 P1 P3 T4 T6 P8 T10 T12 Week T4 T6 P8 Week 70 -• 255-F 60 -• 474-M 50 -A 596-F 40 -S 664-F 30 --0- 795-F 20 --A- 881-F 10 -0 -• 337-M • • 674-M A 775-M e 854-F • 264-F • 574-F A 615-M e 683-F 961-F T6 P8 Week T10 T12 • 326-M • 564-M -A- 624-M e 759-F -0- 841-F A - 921-F T6 P8 Week Figure 2.14 Median distance travelled from center of activity (MDIS) estimates (m) for individual roof rats located during Session 2 (September 20, 1994 - December 10, 1994). Treatment applications indicated by downward arrows. (Legend: symbol for individual, transmitter number - sex) 63 5 0 4 0 3 0 2 0 10 C O N T R O L DMDIT TMT Pre-treatment week 1 C O N T R O L DMDIT TMT Pre-treatment week 3 5 0 4 0 3 0 2 0 10 C O N T R O L DMDIT TMT Treatment week 1 C O N T R O L DMDIT TMT Treatment week 3 Figure 2.15 Mean median distance travelled from center of activity (MDIS) estimates (m) for three treatments (Control, D M D I T and T M T ) by telemetry week during Session 2 Treatment 1 (September 20, 1994 - November 4, 1994). Each value is the mean of at least seven replicates ± standard error (SE). (Legend: symbol for individual, transmitter number - sex) 64 For Session 2 Treatment 2, mean MDIS values ranged from 14-23 m (Fig. 2.16), and no significant differences were found (P=0.19). Proportion of telemetry locations in treated trees: These data were initially plotted by individual (Fig. 2.17) with values ranging between 0-100%. The change in treatments during this session did not appear to have an effect on the number of telemetry readings in treated trees. For individuals present throughout Session 2 Treatment 1 the mean proportion of readings in treated trees ranged from 25-57% (Figure 2.18). No significant differences were found within or between treatment weeks (P=0.53). In Session 2 Treatment 2, the mean proportion of locations in treated trees ranged from 20-77% (Fig. 2.19). There were no significant differences found within or between treatment weeks (P=0.12). 65 5 0 4 0 3 0 2 0 10 C O N T R O L DMDIT T M T Pre-treatment week 8 C O N T R O L DMDIT T M T Treatment week 10 C O N T R O L DMDIT TMT Treatment week 12 Figure 2.16 Mean median distance travelled from center of activity (MDIS) estimates (m) for three treatments (Control, D M D I T and T M T ) by telemetry week during Session 2 Treatment 2 (November 9,1994 - December 10, 1994). Each value is the mean of at least seven replicates ± standard error (SE). (Legend: symbol for individual, transmitter number - sex) 66 • 155-M 194-F A 550-M -B- 646-F 726-F P8 T10 T12 DMDIT Week m 337-M +- 674-M -A- 775-M S 854-F P1 P3 T 5 T7 P8 T10 T12 Week m 214-M + 583-F A 660-M •e 783-F 821 -F •A- 910-M T 5 T7 P8 T10 T12 Week m 264-F ••• 574-F A- 615-M G 683-F -e- 961-F P1 P3 T 5 T7 P8 T10 T12 Week m 255-F • 474-M •A- 596-F S 664-F -©- 795-F -£r 881-F T 5 T7 P8 T10 T12 Week • 326-M ^ 564-M A- 624-M & 759-F -O- 841-F -A- 921-F P1 P3 T 5 T7 P8 | T10 T12 Week DMDIT Figure 2.17 Proportion of telemetry locations in treated trees for individual roof rats in Session 2 (September 20,1994 - December 10, 1994). Treatment applications indicated by downward arrows. (Legend: symbol for individual, transmitter number - sex) 67 0.8 0.7 0.6 -0.5 -0.4 0.3 0.2 0.1 0.0 C O N T R O L DMDIT TMT Pre-treatment week 1 C O N T R O L DMDIT TMT Pre-treatment week 3 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 C O N T R O L DMDIT TMT Treatment week 1 C O N T R O L DMDIT TMT Treatment week 3 Figure 2.18 Mean proportion of telemetry readings in treated trees for three treatments (Control, D M D I T and T M T ) by telemetry week during Session 2 Treatment 1 (September 20, 1994 - November 4, 1994). Each value is the mean of at least three replicates ± standard error (SE). (Legend: symbol for individual, transmitter number - sex) 68 1.0 r 0.8 0.6 0.4 0.2 0.0 C O N T R O L DMDIT TMT Pre-treatment week 8 C O N T R O L DMDIT T M T Treatment week 10 C O N T R O L DMDIT T M T Treatment week 12 Figure 2.19 Mean proportion of telemetry readings in treated trees for three treatments (Control, D M D I T and T M T ) by telemetry week during Session 2 Treatment 2 (November 9, 1994 - December 10, 1994). Each value is the mean of at least three replicates ± standard error (SE). (Legend: symbol for individual, transmitter number - sex) 69 DISCUSSION A concern throughout this study was the individual variability displayed by the roof rat. Ideally one could reduce this variability by increasing the sample size and number of replicates. However, the results from chapter 1 suggested that 2 predator odour treatments should be field-tested which limited the experimental design to 2 replicates for each of 3 treatments. The variable capture rates also indicated cautious interpretation of population parameters. Variable trappability estimates (Table 2.1) was the first indication of potential bias in interpretation of mark-recapture results. I am, however, confident that some of the population parameters based on the mark-recapture information provide worthwhile data as to changes in the trapped population. Many other small mammal population studies recognize this variable trappability when interpreting mark-recapture results (Sullivan 1990, 1994; Nichols and Pollock 1983). Telemetry data were also subject to the effects of small sample sizes with a low number of replicates. Predation, radio-collar slippage and malfunction all contributed to the small samples size of animals especially towards the end of Session 1. Although sample sizes were quite small, the specific individual results from the telemetry analysis provided useful insight into patterns of habitat use. This research addressed five hypotheses, the first of which was: H I : Predator odour treatments will decrease the number of roof rats captured in treated relative to untreated areas. Rats have a history of poor capture success in live trap studies (Worth 1950; Kartman and Lonergan 1955; Lindsey et al. 1973; Chin 1983). Many studies have found rats to become trap-shy 70 following initial capture (Lindsey et al. 1973; Spender and Davis 1950) while others have found rats, particularly juveniles, to become trap-happy (Nichols and Pollock 1983). With these concerns in mind, I used a mark-recapture design based on an earlier successful pilot study. A n important technique in this procedure was to pre-bait traps (locked open) starting four days prior to each trapping week. This should have reduced neophobic responses to the traps and to re-capturing. The methodology used for the pilot study followed small mammal mark-recapture studies in North America (Sullivan 1990; Ransome and Sullivan 1996). I also followed standard operating procedures utilized by the Denver Wildlife Research Center (DWRC) to live trap rodents in the orchard. The mark-recapture results produced highly variable trappability estimates, with particular low estimates suggesting caution in interpretation of related estimates. The mark-recapture assumption of equal capture probabilities among individuals was likely being violated as a result of different trap responses and heterogeneity in the population (Nicolls and Pollock 1983). Therefore, to address this hypothesis, comparisons between actual capture numbers (relative density), were conducted resulting in no significant treatment effect differences in capture numbers. H2: Population dynamics (breeding and body weights) of roof rats will be lower on treatment areas than on control areas. Although capture numbers varied greatly, some useful information regarding the composition of these captures was gained. Because female breeding condition was more difficult to assess and weights fluctuated with pregnancy status, only males were considered for evaluation of breeding condition and body weight. The number of breeding males were not statistically different between treatment grids or between treatment weeks. 71 Mean male body weights did not vary within or between treatment weeks. Most of the declining trend in mean weights can be attributed to a greater proportion of juveniles being captured in weeks subsequent to the initial trapping week. Survival rate estimates were not tested as a result of low trappability estimates and the relatively short mark-recapture sampling period. The modified mark-recapture design in Session 2 resulted in very low capture success resulting in too little data for analysis. This was probably due to the smaller area trapped which decreased the probability of an individual rat encountering a trap. H3: The mean maximum distances moved ( M M D M ) between subsequent capture (mark-recapture) and median distances from center of activity (MDIS) (telemetry) will be greater for roof rats in predator odour treated areas. Previous studies with predator odours and small mammals have indicated movement of animals from treated areas using mark-recapture information (Sullivan and Crump 1984; Sullivan et al. 1988a & 1988b). In this study the treated areas were in patches within the trapping grid, thereby resulting in an uneven distribution of treatment. The M M D M did not differ between treatments or between treatment week. MDIS telemetry data for Session 1, although not statistically significant, indicates a trend of increasing values on the T M T grids. However, this trend was not observed with the Session 2 telemetry data. The hypothesis that predator odour treatments would increase the distance travelled from individual's center of activity was not supported by my results. H4: The proportion of roof rat locations in treated trees will be lower on treatment areas relative to control areas. 72 Individual home range estimates varied greatly for both telemetry sessions. The hypothesis that roof rat home range estimates will increase following predator odour treatment application was not supported by my results. Although not assessed, MDIS and M C P estimates are probably highly correlated as determined in a previous study in the same orchard (Tobin et al. 1996b). Plotting individual locations by treatment week (results not presented in this thesis) indicated that home range locations tended to shift slightly by week. The home range estimates may not be affected by such shifts, but should be addressed in proportion of locations in treated trees (H5) and through further investigation into shifts in center of activity. H5: The number of roof rat locations in treated trees will be lower on treatment areas relative to control areas. The mark-recapture results indicated that the proportion of capture in traps within or adjacent to (within 1 tree) treated trees decreased over the treatment period on the T M T grids though not significantly. This trend was also observed with the Session 1 telemetry data (lower number of locations in treated areas) although statistical differences were not detected. However, the telemetry results from Session 2 do not indicate any treatment differences. The results do not support the hypothesis of lower number of locations in trees treated with semiochemical predator odours. Throughout the entire study, none of the radio-collared rats travelled more than -150 m from its original weekly home range location. This indicates that no rat ever left the grid on which it was originally trapped. The few rats which did travel greater than this distance either had their radio-collar recovered (predation/slippage) or remained stationary underground, which is also likely to have resulted from predation. The live-trapping data also supported this small area of use as no 73 animal tagged on one grid was ever captured on any other grid. These results support similar findings showing that rats do not stray far from their home range (Spender and Davis 1950; Worth 1950; Pippin 1961; Tobin et al. 1996b). A potential explanation for this observation is the high food abundance year-round coupled with a high density of individuals. Population density has been associated with food availability in the Galapagos Islands (Clark 1978), but this should not be a limiting factor in the orchard habitat. Rodents residing in the orchard have an almost continuous availability of nuts due to the prolonged flowering season and extended nut maturation period in Hawaii (Cavaletto 1983). Studies have revealed that the roof rat's diet in the orchard consists almost entirely of macadamia nuts that allow rats to breed year-round in the orchard (Tobin et al. 1993). 74 S U M M A R Y The primary objective of this study was to examine the effects of synthetic predator odours on the population parameters and movements of wild roof rats. Laboratory results from chapter 1 indicated that responses to the predator odour could be detected by combining the results from various measures of observed behaviours. This descriptive summary approach has been utilized to combine results from various types of measurements (ie. behavioural observations) and utilize non-parametric analysis (Vernet-Maury et al. 1984). From the odour-testing arena, roof rats were observed to delay before entering, delay before first eating bout, spend less time in the arena, take a lower number of eating bouts and consume less food in the presence of D M D I T odour. Mongoose feces odour also produced similar "avoidance" responses although also not statistically significant. T M T and M M P synthetic predator odours also had "avoidance" trends on roof rats. These results support those other laboratory findings where avoidance or fear responses were recorded in rodents while in the presence of predator odours (Vernet-Maury et al. 1984, 1992; Calder and Gorman 1991; Epple et al. 1993; Jedrezejewski et al. 1993). A study conducted using the same laboratory arena with modifications to the design and procedure found no difference in variables measured while testing mongoose odour treatments (odour and urine) (Tobin et al. 1996a). The non-significant results reflect the findings in my study, however different variables were measured over a different time period which may have contributed to a lack in observed descriptive trends. This same study (Tobin et al. 1995) also found lower capture rates in live-traps soiled with mongoose feces in the field portion of the study. The results of the field trials found no differences in roof rat responses to D M D I T and T M T semiochemical treatments. A lack of response to the predator odour treatments may be a result of 75 important habitat values present in the macadamia orchard: abundance of food, water and cover. Other small mammal studies have demonstrated the value of cover relative to the presence of predator odour, finding that in fact, cover may be a more important factor (Merkens et al. 1991). The lack in response may also be attributed to improper methodology to detect the response, or effectiveness of odour release devices. Another potential explanation for the results may be roof rat habituation to the odours or a lack of recognition as the semiochemicals were based on predator species not established in Hawaii. Although some studies have results indicating genetic recognition of odours (Gorman 1984; Vernet-Maury et al. 1984, Boag and Mlotkiewicz 1994), this theory is difficult to test and perhaps learned behaviour is more of a factor in this case. The roof rat's resilient nature probably allows for this adaptability, and many studies have indicated the roof rat's ability to learn new behaviours (Berdoy and MacDonald 1991; Galef and Whiskin 1994). Methodology changes in future research into predator odour effects on roof rats should include a mark-recapture design that samples intensively over a short period of time with longer intervals between sampling and use closed population analysis techniques. These closed population techniques have models which can allow for unequal capture probabilities which seem to be occurring in this study. Pooling the Jolly-Seber estimates has also been suggested to increase precision when capture probabilities are low (Pollock 1982). This option is currently being explored with the data from this study to further assess the merits of open population techniques. Telemetry techniques should continue to be utilized as they provide specific information on individual movements. A n important telemetry measurement to consider is that of shifts in center of activity. This could have been occurring in this study and may not have been properly addressed in the home range estimates and proportion of readings in treated trees. 76 For future studies, the important habitat structure of cover should also be explored through cover manipulation experiments coupled with mark-recapture and/or telemetry techniques. Future odour testing studies should focus on a population of rats that is well understood with respect to population parameters and movement patterns with a treatment design maximizing the number of replicates. Whereas results from the field study did not indicate semiochemical avoidance, recent findings with roof rat avoidance to mongoose feces in the field (Tobin et al. 1995) imply that potential responses may exist. Although semiochemicals from mongoose feces were not available at the time of this study, research into roof rat's response to this predator odour is recommended based on the laboratory findings of this study and recent field results (Tobin et al. 1995). 77 R E F E R E N C E S Atkinson, I.A.E. 1985. The spread of the commensal species of Rattus to oceanic islands and their effects on island avifauna. International Council for Bird Preservation Technical Publication 3:35-84. Berdoy, M . , and MacDonald, D .W. 1991. Factors affecting feeding in wild rats. Acta Ecolog. 12(2):261-279. Boag, B. , and Mlotkiewicz, J.A. 1994. Effect of odor derived from lion faeces on behavior of wild rabbits. J. Chem. Ecol. 20:631-637. Buckle, A.P . , and Fenn, M . G . P . 1992. Rodent control in the conservation of endangered species, pp. 36-41, in J.E. Borrecco and R . E . Marsh, (eds.). Proc. 15th Vertebrate Pest Conference. Univ. Cal., Davis. Calder, C .J . , and Gorman, M . L . 1991. The effect of red fox Vulpes vulpes faecal odours on the feeding behaviour of Orkney voles Microtus arvalis. J. Zool. London 224:599-606. Carpenter, S.R., Frost, T . M . , Heisey, D. , and Kratz, T . K . 1989. Randomized intervention analysis and the interpretation of whole-ecosystem experiments. Ecology 70:1142-1152. Cattarelli, M . , and Chanel, J. 1979. Influence of some biological meaningful odorants on the vigilance states of the rat. Physiol. Behav. 23:831-838. Cavaletto, C . G . 1983. Macadamia nuts, pp. 361-379, in H . T . Chan Jr. (ed.). Handbook of Tropical Foods. Marcel Dekker Inc., New York. Chin, M . 1983. Home range and abundance of black rats in citrus groves, Madera County, California. M . A . thesis. Dept. of Biology. California State University, Fresno. 111 p. Chance, M . R . A . , and Mead, A .P . 1955. Competition between feeding and investigation in the rat. Behav. 8:174-182. Clark, D.B. 1980. Population Ecology of Rattus rattus across a Desert-Montane forest gradient in the Galapagos Islands. Ecology 61(6): 1422-1433. Clark, D .A. 1978. Black rat (Rattus rattus) feeding ecology in the Galapagos Islands, Rattus rattus and Oryzomys bauri. Ph.D. Thesis. Univ. of Wisconsin, Madison. 196 p. Engeman, R . M . , and Pank, L . F . 1984. Potential secondary toxicity from anticoagulant pesticides contaminating human food sources. New England J. Med. 311:257-258. Epple, G.J . , Mason, R., Nolte, D . L . , and Campbell, D . L . 1993. Effects of predator odors on feeding in the mountain beaver (Aplodontia rufa). J. Mammal. 74(3):715-722. 78 Ewer, R. F . 1971. The biology and behaviour of a free-living population of black rats (Rattus rattus). Anim. Behav. Monogr. 4:127-174. Galef, B . G . Jr., and Whiskin, E . E . 1994. Passage of time reduces effects of famikarity on social learning: Functional implications. Anim. Behav. 48(5): 1057-1062. Gorman, M . L . 1984. The response of prey to Stoat (Mustela erminea) scent. / . Zool. Lond. 202:419-423. Gratz, N . G . 1992. Rodents as carriers of disease, pp. 85-108, in A . P . Buckle and R . H . Smith (eds.). Rodent Pests and their Control. C A B International. Cambridge University Press. 405 p. Hawaii Agricultural Statistics Service 1992. Hawaii macadamia nuts, final season estimates. U.S. Dept. A g r i c , Honolulu. 8 p. Heale, V . R . , and Vanderwolf, C . H . 1994. Toluene and weasel (2-propylthietane) odors suppress feeding in the rat. J. Chem. Ecol. 20:2953-2958. Jedrzejewski, W . , Rychlik, L . , and Jedrzejewska, B . 1993. Responses of bank voles to odours of seven species of predators: experimental data and their relevance to natural predator-vole relationships. Oikos 68:251-257. Kartman, L . , and Lonergan, R.P. 1955. Observations on rats in an enzootic plague region of Hawaii. Public Health Report, Communicable Disease Center Hawaiian Field Station. Krebs, C.J . 1991. Small mammal programs for mark-recapture data analysis. Dept. of Zoology, University of British Columbia, Vancouver, B C . 35 p. Krebs, C.J., and Boonstra, R. 1984. Trappability estimates for mark-recapture data. Can. J. Zool. 62:2440-2444. Krebs, C.J. 1966. Demographic changes in fluctuating populations of Microtus californicus. Ecol. Monogr. 58. 70 p. Lindsey, G.D. , Nass, R.D. , Hood, G . A . , and Hirata, D . N . 1973. Movement patterns of Polynesian rats (Rattus exulans) in Sugarcane. Pac. Sci. 27(3):239-246. Lindsey, G.D. , Nass, R.D. , and Hood, G .A . 1971. A n evaluation of bait stations for controlling rats in sugarcane. J. Wildl. Manage. 35:440-444. Lund, M . 1994. Commensal rodents, pp. 23-43, in A .P . Buckle and R . H . Smith (eds.). Rodent Pests and their Control. C A B International, Wallingford, U . K . Manly, B.F.J . 1990. Randomization and Monte Carlo Methods in Biology. Chapman & Hal l , New York. 79 Merkens, M . , Harestad, A .S . , and Sullivan, T.P. 1991. Cover and efficacy of predator-based repellents for Townsend's vole, Microtus townsendii. J. Chem. Ecol. 17:401-412. Nichols, J.D., and Pollock, K . H . 1983. Estimation methodology in contemporary small mammal capture-recapture studies. J. Mammal. 64:253-260. Pippin, W . F . 1961. The distribution and movement of roof rats on Mona Island, West Indies. J. Mammal. 42(3):344-348. Pollock, K . H . 1982. A capture-recapture design robust to unequal probability of capture. J. Wildl. Manage. 46(3):752-757. Prakash, I. 1988. Bait shyness and poison aversion, in I. Prakash (ed.). Rodent Pest Management. C R C Press, Boca Raton. Ransome, D .B . , and Sullivan, T.P. 1996. Food limitations and habitat preference of Glaucomys sabrinus and Tamiasciurus hudsonicus. J. Mammal. (In press). Ritchie, C , and Sullivan, T.P. 1989. Monitoring methodology for assessing the impact of forest herbicide use on small mammal populations in British Columbia. British Columbia Ministry of Forests, F R D A Report 081. 23 p. Sakai, W.S. , and Nagao, M . A . 1984. Fruit growth and abscission in Macadamia integrifolia. Physiol. Plant. 64:455-460. SAS Institute Inc. 1988. S A S / S T A T user's guide, release 6.03 edition. SAS Institute Inc., Cary, N C . 1028 p. Saville, D.J. 1990. Multiple comparison procedures: the practical solution. Amer. Stat. 44:174-180. Scheiner, S .M. , and Gurevitch, J. 1993. Design and analysis of ecological experiments. Chapman and Hall, New York. 445 p. Spencer, H.J . , and Davis, D . E . 1950. Movement and survival of rats in Hawaii. 7. Mammal. 31:154-157. Stone, C P . 1985. Alien animals in Hawai'i's native ecosystems: toward controlling the adverse effects, pp. 251-297, in C P . Stone and J . M . Scott (eds.). Hawai'i's terrestrial ecosystems: preservation and management. Cooperative National Park Resources Studies Unit, Honolulu. Stuwe, M . , and Blohowiak, C . E . 1989. McPaal micro-computer programs for the analysis of animal locations. Conservation and Research Center, National Zoological Park, Smithsonian Institution. Sugiahara, R . T . , Tobin, M . E . , and Koehler, A . E . 1985. Zinc phosphide baits and prebaiting for controlling rats in Hawaiian sugarcane. J. Wildl. Manage. 59:882-889. 80 Sullivan, T.P. 1994. Influence of herbicide-induced habitat alteration on vegetation and snowshoe hare populations in sub-boreal spruce forest. J. Appl. Ecol. 31:717-730. Sullivan, T.P. 1990. Responses of Red squirrel (Tamiasciurus Hudsonicus) populations to supplemental food. / . Mammal. 71(4):579-590. Sullivan, T .P . , and Cheng, C . 1990. Use of encapsulated predator odour repellents to protect coniferous plantations from feeding damage by Black-tailed deer. Forestry Canada Final Report, Vicotria, B . C . 19 p. Sullivan, T .P . , Crump, D.R. , and Sullivan, D.S. 1988a. The use of predator odor repellents to reduce feeding damage by herbivores. III. Montane (Microtus montanus) and meadow (M. pennsylvanicus) voles. J. Chem. Ecol. 14:363-377. Sullivan, T .P . , Crump, D.R. , and Sullivan, D.S. 1988b. The use of predator odor repellents to reduce feeding damage by herbivores. IV. Northern pocket gophers (Thomomys talpoides). J. Chem. Ecol. 14:379-389. Sullivan, T.P., Sullivan, D.S., Crump, D.R., Weiser, H . , and Dixon, E . A . 1988c. Predator odors and their potential role in managing pest rodents and rabbits. Proc. Vertebr. Pest Conf. 13:145-150. Sullivan, T.P. , and Crump, D.R. 1986. Avoidance response of pocket gophers (Thomomys talpoides) to mustelid anal gland compounds, pp. 519-531, in D . Duvall, D. Muller-Schwarze, and R . M . Silverstein (eds.). Chemical Signals in Vertebrates IV. Plenum Press, New York. Sullivan, T.P., and Crump, D.R. 1984. Influence of mustelid scent-gland compounds on suppression of feeding by snowshoe hares (Lepus americanus). J. Chem. Ecol. 10:1809-1821. Tamarin, R . H . , and Malecha, S.R. 1972. Reproductive parameters in Rattus rattus and Rattus exulans of Hawaii, 1968 to 1970. J. Mammal. 53:513-528. Tobin, M . E . 1992. Rodent damage in Hawaiian Macadamia Orchards, pp. 272-276, in J .E . Borrecco and R . E . Marsh, (eds.). Proc. 15th Vertebrate Pest Conference. Univ. Cal. , Davis. Tobin, M . E . , Koehler, A . E . , Sugihara, R .T . , and Burwash, M . D . 1996a. Repellency of mongoose feces and urine to rats (Rattus spp.). Repellents Symposium (in press). Tobin, M . E . , Sugihara, R .T . , Koehler, A . E . , and Ueunten, G.R. 1996b. Seasonal comparison of Rattus rattus (Rodentia, Muridae) in a Hawaiian macadamia nut orchard. Mammalia 60(1):3-13. Tobin, M . E . , Engeman, R . M . , and Sugihara, R .T . 1995. Effects of mongoose odors on rat capture success. / . Chem. Ecol. 21(5):635-639. Tobin, M . E . , Koehler, A . E . , Sugihara, R .T . , Ueunten, G . , and Yamaguchi, A . M . . 1993. Effects of trapping on rat populations and subsequent damage and yields of macadamia nuts. Crop Prot. 12:243-248. 81 Tobin, M . E . , Sugihara, R.T. , and Ota, A . K . 1990. Rodent damage to Hawaiian Sugarcane, pp. 120-123, in L . R . Davis and R . E . Marsh (eds.). Proc. 14th Vert. Pest Conf. Univ. Cal. , Davis. Tomich, P.Q. 1986. Mammals in Hawaii. 2nd ed. Bishop Museum Press, Honolulu, 375 p. Tomich, P.Q. 1970. Movement patterns of field rodents in Hawaii. Pac. Sci. 24:195-234. Vernet-Maury, E . 1980. Trimethyl-thiazoline in fox feces: A natural alarming substance for the rat, p. 407, in H . van der Starre (ed.). Proceedings of the VII International Symposium on Olfaction and Taste. IRL Press, London. Vernet-Maury, E . , Constant, B. , and Chanel, J. 1992. Repellent effect of trimethyl thiazoline in the wild rat Rattus norvegicus berkenhout, in R . L . Doty and D . Muller-Schwarze (eds.). Chemical Signals in Vertebrates VI. Plenum Press, New York. Vernet-Maury, E . , Polak, E . H . , and Demael, A . 1984. Structure-activity relationship of stress-inducing odorants in the rat. J. Chem. Ecol. 10:1007-1018. Worth, C . B . 1950. Field and laboratory observations on roof rats, Rattus rattus (Linnaeus), in Florida. J. Mammal. 31(3):293-304. Xu , Z. , Stoddart, D . M . , Ding, H . , and Zhang, J. 1996. Self-anointing behavior observed in the rice-field rat, Rattus rattoides. J. Chem. Ecol. (in press). 82 

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