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Texas A&M University (2015)

Home Range, Reproduction, and Survival of the Desert Kit Fox, Southeastern, California

Randel III, Charles J

Titre : Home Range, Reproduction, and Survival of the Desert Kit Fox, Southeastern, California

Auteur : Randel III, Charles J

Université de soutenance : Texas A&M University

Grade : Doctor of Philosophy (PhD) 2015

Kit foxes (Vulpes macrotis) are small, nocturnally active, arid-land foxes found in semi-arid and desert climates in western North American and northern Mexico. Two kit fox subspecies : the federally endangered and state threatened San Joaquin kit fox (V. m. mutica) and the desert kit fox (V. m. arsipus) occur in geographically distinct ranges in California. The majority of kit fox research has focused on the San Joaquin kit fox due to its state and federal status, with relatively few studies conducted on California’s desert kit fox populations, a fully protected species in California. A 2-year radio-telemetry study of the desert kit fox was conducted to determine the following life history traits : home range, home range overlap among individuals, population density, reproductive parameters, seasonal and annual survival, and cause-specific mortality sources in the Upper Chuckwalla Valley, Riverside County, California. Fifty-six desert kit foxes were captured and fitted with mortality-sensitive radio-collars and tracked from October 2012 to August 2014. Individuals were located 5–7 times per week, and nightly locations were used to estimate seasonal and annual fixed kernel and minimum convex polygon home range size, seasonal and annual survival, and morality location and dates. Additionally, radio-telemetry was used to identify natal den complexes for direct monitoring, to determine reproductive success, and to obtain litter size. Based on 95% fixed kernel or MCP estimators There was no difference (P = 0.820) between home range sizes of males and females, with mean home range sizes of 15.77 ± 1.03 km² (95% fixed kernel) and 18.48 ± 1.77 km² (MCP), respectively. Similarly, there was no statistically significant difference in seasonal (e.g., pair formation [P= 0.855], pup-rearing [P= 0.205], and dispersal [P= 0.180]) home range sizes based on sex or year. Annual home range overlap was significantly larger for mated pairs (79.3 ± 1.35%) than unmated pairs (20.9 ± 1.01%), and this is consistent with patterns for other populations of other kit foxes. Densities in the study area were 0.18 ± 0.05/km². Reproductive success in 2013 and 2014 did not vary, with 50% of females producing ≥1 pup annually. Mean litter size was 2.69 ± 0.30 (SE, range 1–6) and mean reproductive rate was 1.35, with no statistically significant difference (χ² = 0.001, P = 0.97) between years. Annual survival rates for desert kit fox ranged from 0.752–0.885, and survival rate was 0.674. Similar to previous studies, coyote (Canis latrans) predation was the primary source of mortality during this study. Larger than average home range size coupled with a low reproductive rate may have been influenced by drought and the associated prey availability. Previous research of kit foxes in California’s Central Valley and Utah’s Dugaway Proving Grounds found both home range size and reproduction were influenced by prey availability, which is known to be adversely affected by drought conditions.


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