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Fisher population ecology on the Hoopa Valley Indian Reservation, northwestern California
I studied aspects of fisher (Martes pennanti) population ecology on the Hoopa Valley Indian Reservation in northern California to fill critical information gaps relative to timber management and its effect on the status of fishers, a candidate for listing under the U.S. Endangered Species Act. A decline in mark-resight density estimates of fishers from 1998 (52/100 km2; 95% CI = 43–64) to 2005 (14/100 km2; 13–16) was likely due to changes in prey habitat suitability, increased predation pressure, and/or disease. The decline was also indicated by catch-per-unit effort indices, but not by camera station or track-plate station indices. Colleagues and I developed and tested methods of collecting mark-recapture data using genetic marking, passive integrated transponder (PIT) tag technology, and digital, passive-infrared photography that could be used in a demographic monitoring protocol. The comparatively high cost of PIT tag reading equipment and genetic analyses makes the use these methods dramatically more expensive and yield less demographic data compared to using a traditional mark-recapture approach using only live trapping. By monitoring 40 radio-marked, breeding age (≥ 2 years old) females during 2005–2011, we found that 87% exhibited denning behavior and 65% of these were successful in weaning at least one kit (mean = 1.9). Of 14 kits radio-marked in their first fall, 3 died prior to dispersal, 3 lost collars, and the other 8 established home ranges 0.8–18.0 km away from natal areas. Nipple size (width multiplied by height of the largest anterior nipple), evaluated as a predictive index of female fisher reproductive success, differed among nonbreeders vs. attempted and current breeders. A predictive index for use in assigning reproductive status to females with unknown reproductive histories had an overall correct classification rate of 81% and a chance-corrected measure of prediction of 69.5%. These results illustrate the value in establishing long-term, accurate programs to monitor populations of imperiled species which strive to determine cause and affect relationships to changes in populations and ultimately, modeling habitat fitness. The relatively low reproductive rate of female fishers brings into question the species ability to demographically respond to increased rates of juvenile and adult mortality with increased reproduction and/or survival. The limited dispersal capability of juvenile fishers restricts ability to rescue vanishing local populations from extirpation, re-inhabit landscapes from which they were previously extirpated, and establish the functional connectivity of metapopulations.
Wildlife Conservation|Wildlife Management|Ecology|Natural Resource Management
Matthews, Sean Michael, "Fisher population ecology on the Hoopa Valley Indian Reservation, northwestern California" (2012). Doctoral Dissertations Available from Proquest. AAI3518259.