Syntopy between Endangered San Joaquin Kit Foxes and Potential Competitors in an Urban Environment.

The endangered San Joaquin kit fox (Vulpes macrotis mutica; SJKF) occurs in the city of Bakersfield, CA, where several putative competitors also occur, including domestic cats (Felis catus), striped skunks (Mephitis mephitis), raccoons (Procyon lotor), and opossums (Didephis virginiana). We used data from a multi-year (2015-2022) city-wide camera station survey to assess whether the other species were simply sympatric with SJKF or coexisting syntopically (i.e., occurring in the same habitats without apparent competition). Annual detection rates for the other species were not correlated with SJKF rates either within SJKF habitat suitability categories (low, medium, and high) or for all categories combined. Also, detection rates for the other species did not increase in response to a significant decline in SJKF abundance caused by sarcoptic mange. The use of all SJKF habitat suitability categories by the other species and co-detections with SJKF at camera stations indicate high spatial overlap. Interference and exploitative competition between the species are apparently negligible, likely due to similar body sizes and high resource abundance. Thus, SJKF and the other species appear to be coexisting syntopically in the urban environment, resulting in a significant additional SJKF population that facilitates range-wide conservation and recovery of this endangered species.

MOVEMENTS BY SAN JOAQUIN KIT FOXES (VULPES MACROTIS MUTICA) BETWEEN URBAN AND NONURBAN HABITATS: IMPLICATIONS FOR INTERPOPULATION DISEASE TRANSFER.

Sarcoptic mange epidemics erupted in two of the remaining populations of endangered San Joaquin kit foxes (Vulpes macrotis mutica). Both populations are in urban habitats in the cities of Bakersfield and Taft, California, USA. The risk of disease spread from the two urban populations to nearby nonurban populations, and then throughout the species range, is of considerable conservation concern. To date, mange has not been detected in any nonurban populations despite considerable surveillance effort. The reasons for the lack of detections of mange among nonurban foxes are unknown. We monitored urban kit fox movements using geographic positioning system (GPS) collars to test the hypothesis that urban foxes were not venturing into nonurban habitats. Of 24 foxes monitored December 2018 to November 2019, 19 (79%) made excursions from urban into nonurban habitats from 1-124 times. The mean number of excursions per 30 d was 5.5 (range 0.1-13.9 d). The mean proportion of locations in nonurban habitats was 29.0% (range 0.6-99.7%). The mean maximum distance that foxes traveled into nonurban areas from the urban-nonurban interface was 1.1 km (range 0.1-2.9 km). Mean number of excursions, proportion of nonurban locations, and maximum distance into nonurban habitats were similar between Bakersfield and Taft, females and males, and adults and juveniles. At least eight foxes apparently used dens in nonurban habitats; shared use of dens may be an important mode of mange mite transmission between conspecifics. Two of the collared foxes died of mange during the study and two others had mange when captured at the end of the study. Three of these four foxes had made excursions into nonurban habitats. These results confirm a significant potential for mange to spread from urban to nonurban kit fox populations. We recommend continued surveillance in nonurban populations and continued treatment efforts in the affected urban populations.

Intraguild Competition between Endangered Kit Foxes and a Novel Predator in a Novel Environment.

A population of endangered San Joaquin kit foxes inhabits the urban environment in the city of Bakersfield, California, United States. This population is considered important for the conservation and recovery of this species. In this novel environment, kit foxes encounter a novel competitor, that being non-native red foxes. We examined exploitative and interference competition between these two species. Based on scat analysis, both species consumed similar foods and dietary overlap was high. Red foxes also were found to usurp kit fox dens. Direct mortality to kit foxes from red foxes appears to be rare. Kit foxes and red foxes also appear to overlap spatially, although we found evidence of temporal partitioning of shared space. Based on binary logistic regression modeling, habitat attributes in grid cells used by the two species generally were similar, consistent with the spatial overlap. However, differences in specific attributes indicated that kit foxes are more likely to use areas with smaller open spaces and more human activity compared to red foxes. Competition from red foxes may be mitigated by several factors. Critical resources such as food and dens may be sufficiently abundant such that they are not a limiting factor. Some degree of spatial segregation and temporal partitioning of shared space may reduce interference competition. These factors may facilitate coexistence, and consequently, red foxes do not currently appear to constitute a significant competitive risk to this important population of endangered San Joaquin kit foxes.