Trends in Fisher Predation in California A focus on the SNAMP fisher project

Transcription

1 Trends in Fisher Predation in California A focus on the SNAMP fisher project Greta M. Wengert Integral Ecology Research Center UC Davis, Veterinary Genetics Laboratory gmwengert@ucdavis.edu Project Collaborators: Mourad Gabriel, Rick Sweitzer, Reginald Barrett, Craig Thompson, Kathryn Purcell, J. Mark Higley, Sean Matthews, Aaron Facka, Roger Powell, Deana Clifford

2 Intraguild Predation in Carnivore Communities Intraguild Predation: predation of one species on another within the same guild that also compete for a shared prey Common in many carnivore communities Can regulate carnivore populations Can also be compensatory May be habitat-mediated

3 Predation on Fishers: A Historical Perspective **Predation does not occur on healthy, adult fishers **Predation mostly important for translocated fishers **Predation is not a limiting factor for fisher populations **Until this study, documented predation in CA: coyotes, raptors, other fishers

4 Understanding Predation in California Fisher Communities Predation patterns throughout California How common is it? Who are the predators? Importance of predation for fisher populations Ecology of predators as it relates to fishers Managing for predation of fishers

5 Fisher Predation in California Hoopa Fisher Project California Fisher Translocation SNAMP Fisher Project Kings River Fisher Project Predation ranks as highest cause of mortality ~ 60% of all documented fisher mortalities

6 Identifying the predators of fishers Look for bite wounds, verify ante-mortem (hemorrhaged) wounds through necropsy Photograph and measure bite wounds: width of puncture, breadth between punctures

7 Collecting Possible DNA Swab bite wounds (Synthetic-tipped swabs) Collect matted fur around the bite wounds (with potential predator saliva or blood) Collect hairs that do not belong to the fisher

8 Molecular Methods - PCR Felid-specific primers Canid-specific primers Variable regions of these loci allow for accurate identification of species. HV1 region of D-loop

9 Who Are the Fisher Predators in CA? Bobcat Mountain lion Coyote

10 Predator Patterns Across Projects in California Fisher predators 60% killed by bobcats 33% killed by mountain lions 7% killed by coyotes Of DNA-confirmed predators: Most female fishers killed by bobcats Adult male fishers killed by mountain lions

11 Genetic Analyses of SNAMP Bobcats Individual identities of bobcats Of 8 bobcat-killed fishers: Four bobcats responsible Bobcat 1 killed three fishers Bobcat 2 killed three fishers Bobcat 3 killed one fisher Bobcat 4 killed one fisher Photo: SNAMP Bobcat 2 is male At least two mountain lions killed four fishers (maybe more) Photo: SNAMP

12 Distribution of Bobcat Predation at SNAMP Same male bobcat Same bobcat (unknown sex)

13 Predation on Fishers: Current Thoughts **Predation frequently occurs on healthy, adult fishers **Predation may be important for resident fishers (in addition to translocated fishers) Still unknown: is predation a limiting factor?

14 Is predation a limiting factor? Golden eagle (Aquila chrysaetos) presence caused sharp decline in Channel Island fox abundance, threatening extinction Predation probably compensatory for many species May be very important for already small, compromised populations

15 Recent Work on Fisher Survival Spencer et al. (2011) states: BUT even modest increases in mortality rates (10 20%) could prevent population expansion We do not know if predation is additive (or, exceeds the normal rate of predation the California fisher populations evolved with)

16 How do we answer that question? Derive some index of bobcat or lion population dynamics over the years Determine if bobcat populations increased during the 20 th century, possibly using trapping records Determine if predation rates correspond with bobcat population size Understand how bobcat or lion populations respond to habitat changes

17 Some Data on Bobcat Habitat Litvaitis et al. (2006): bobcat population size positively related to cover of second-growth forest in New Hampshire Witmer and decalesta (1986): bobcats in Oregon forests used all habitat types in proportion to availability (clear-cut, shrub, forest) No data from CA forest bobcats

18 Predator Ecology and Fishers Understand the ecology of predation focus on most important fisher predator - bobcat Characterize spatial predation risk Determine high-risk habitats for fishers for bobcat interaction

19 Current Research on Bobcat-Fisher Relationships Habitat selection and space use by bobcats at Hoopa Spatial relationship between bobcats and fishers Avoidance? Spatial overlap? Habitat types most prone to bobcat-fisher interaction Compare to actual predation sites Evaluate spatial or habitat mediation of predation risk Diet composition potential for competitive interactions

20 Three Bobcats Collared at Hoopa Two adult males, one adult female Currently, the males are being tracked One with GPS collar, one with radio-collar

21 Bobcat Home Range and Habitat Use Use telemetry on bobcats to assess landscape scale and stand-level space use and home range Develop model of bobcat habitat selection in mixed coniferous forest

22 Determine High-Risk Habitats for Fishers Characterize habitats where at least one location each of a bobcat and fisher occurs within 100m Develop habitat model of high-risk habitats for bobcat-fisher interactions

23 Assess Prey Resource Overlap Fecal analysis for diet composition Compare between bobcats and fishers Assess potential for competition for prey

24 Conclusions on Fisher Predation Predation on fishers occurs frequently Is not biased towards young fishers May not be biased towards female fishers, but is likely more important for females Most common predators are bobcats and mountain lions We need to better understand the ecology of intraguild predators of fishers, **And, how predation impacts fisher populations

25 Acknowledgments Financial Support California Department of Fish and Game Integral Ecology Research Center USFS Sierra Nevada Research Center U.C. Berkeley/ SNAMP Hoopa Valley Tribe U.S. Fish and Wildlife Service, Yreka Office California Animal Health and Food Safety Lab U.C. Davis Canid Diversity and Conservation Lab Humboldt Area Foundation Logistic Support U.C. Davis Veterinary Genetics Laboratory, Forensics Unit Field crews at SNAMP, Kings River Fisher Project, Hoopa Valley Fisher Project, California Fisher Translocation Wildlife Conservation Society U.C. Davis Center for Population Biology California Animal Health and Food Safety Laboratory UC Davis Veterinary Medical Teaching Hospital UCD Pathologists: Leslie Woods, Linda Munson, Stefan Keller, Patty Gaffney, Megan Jones