Home range, site fidelity, reproductive ecology, and den site characteristics of the San Clemente Island fox

Resnik, Jessica Ruth, author
Andelt, William F., advisor
Savidge, Julie A., committee member
Stanley, Thomas R., committee member
Theobald, David M., committee member
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Since 2004, the endangered status of 4 island fox (Urocyon littoralis) subspecies has prompted increased efforts to understand and manage island foxes on all 6 islands where they occur. High rates of vehicle-related mortalities and potential for exposure to pathogens are of particular concern on San Clemente Island, California. Basic spatial ecology of the San Clemente Island fox (U. l. clementae) is needed for effective management but is currently inferred from home range studies on other island fox populations. Additionally, little is known about reproduction and denning of this subspecies, and island foxes in general. To better inform management strategies, I studied the spatial and reproductive ecology of this subspecies. During 2006-2007, I collected telemetry locations throughout the diel period for a random sample of foxes (n = 29), a sample with home ranges that included roads (n = 18) and a sample with home ranges that excluded roads (n = 19). I also monitored the movements of females in the random sample during 2007 to determine the proportion producing litters, number of kits in weaned litters, chronology of reproduction, and den site characteristics. I found that San Clemente Island foxes had home ranges (mean = 0.75 km2, SE = 0.9) and core areas (mean = 0.19 km2, SE = 0.03) 36-116% larger than reported in published studies for other island fox subspecies. Home ranges were largest during the pup-independence season (mean = 0.76 km2, SE = 0.07), but did not vary between pup-dependence (mean = 0.68 km2, SE = 0.11) and breeding (mean = 0.66 km2, SE = 0.10) seasons. Core area sizes were similar among all seasons. Annual home ranges and core areas for foxes living near roads were 77% and 82% larger compared to non-road foxes. Seasonal home ranges were larger for road foxes than for non-road foxes during the pup-independence and breeding seasons, but were similar in size during the pup-dependence season. Site fidelity between seasons ranged from 18-50%, was greater for home ranges of males than females, and was not different between genders for core areas. I did not detect dispersal during the home range study. Only 3 or 4 of 23 females produced a total of 6 pups. Of 13 females recaptured and examined for reproductive status, most had lactated in previous years (n = 7), or had some evidence of lactating but not weaning pups (n = 4); two females had never lactated. Breeding and parturition occurred two months earlier than reported for other island fox subspecies in wild-born or captive breeding populations since the 1970s. Females used two or three dens in succession and dens were almost exclusively found in rock crevices. Five of 23 foxes had home ranges that included supplemental food sources and human habitation, including all four females observed with pups, suggesting this could be a factor in reproductive success. I recommend caution when generalizing findings from other island fox subspecies and suggest managers establish subspecies-specific information to better inform conservation strategies on the different islands.
2012 Spring.
Includes bibliographical references.
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