We describe four case studies in central California in which young San Joaquin kit fox (Vulpes macrotis mutica) pups were orphaned and either fostered for a period of time in captivity and released, or provisioned entirely in the wild by caretakers. In February 1992, six pups whose mother had died by predation were temporarily fostered in captivity. Four of the pups were then placed in the den of their father and an unrelated female (Case 1) and the remaining two pups were placed with an entirely unrelated family group (Case 2). In April 2019, a mother of five pups died by vehicle strike. These pups appeared to be weaned though no other adults were present, so they were provisioned at their natal den (Case 3). In spring 2022, one abandoned pup was hospitalized for sarcoptic mange concurrently with an unrelated family group consisting of an adult female and her three pups. The orphaned pup was introduced into the family group while in captivity and all were released together after recovery (Case 4). Of the 12 orphaned pups in all cases, at least seven survived till dispersal age, two survived into the following year, and one reproduced.

A population of endangered San Joaquin kit foxes (Vulpes macrotis mutica) occurs in the city of Bakersfield, CA.  In spring 2013, sarcoptic mange was detected in this population and the disease quickly spread.  In January 2019, the disease appeared in a smaller kit fox population in nearby Taft, CA.  Over the last 9 years there have been over 474 reports of kit foxes with mange, 100 confirmed deaths, 141 foxes treated in the field, and 155 foxes treated at the California Living Museum (CALM).  In conjunction with treating foxes, the Endangered Species Recovery Program (ESRP) has also conducted an annual citywide camera survey in Bakersfield since 2015 and Taft since 2019 to assess mange among kit foxes and its spatial spread.  The data collected is consistent with opportunistic sightings, trapping efforts, and reports from the public, all of which indicate a substantial decline in the urban kit fox population.  The periodic confirmation of healthy foxes throughout both urban areas as well as population modeling indicates that the disease will remain indefinitely.  Mange response, camera survey monitoring, and research projects will continue in order to treat sick foxes and further study the effects of mange on the urban kit fox population.  

San Joaquin kit foxes (Vulpes macrotis mutica) are listed as Federally Endangered and California Threatened, primarily due to profound habitat loss throughout their range. The San Joaquin kit fox now persists in a metapopulation consisting of three main “core” populations, one of which is in Panoche Valley California. In spring of 2019, following the completion of the Panoche Valley Solar Farm, a 3-year investigation of ecological and demographic traits of San Joaquin kit foxes within Panoche Valley was initiated to determine how the population is affected by this anthropogenic disturbance. To investigate these effects, kit foxes were monitored on two sites within Panoche Valley. The solar site was located within a 1.5-km buffer of the Panoche Valley Solar Farm arrays and the reference site was located on Silver Creek Ranch in relatively undisturbed habitat. Kit foxes were collared with GPS collars and tracked regularly to dens and resting areas. Over the course of the study, 99 individual foxes were captured and we were able to determine the size and space use of 77 foxes. We also documented similarities and differences in reproduction, survival, mortalities, and diet between the two sites.

We assessed demographic and ecological patterns of endangered San Joaquin kit foxes (Vulpes macrotis mutica) relative to resource and competitor abundance in the Carrizo Plain National Monument (CPNM) during 2014 to 2019. Based on prey sign surveys, abundance of kangaroo rats and rabbits increased from 2014 to 2019. Kangaroo rats increased in kit fox diets while the rabbits and rodents increased in coyote diets. Visitation rates by both kit foxes and coyotes increased during the study, and the proportion of individual stations that were visited by both species also increased. We used GPS collars to examine kit fox survival, reproduction, and space use in a year of low prey availability (2015-16) and a year of high prey availability (2017-18). Kit fox survival was 0.69 in 2015-16 and 0.87 in 2017-18. Reproductive success was 44.4% in 2015-16 and 72.7% in 2017-18. Mean home range size was 4.3 km2 in 2015-16 and 1.3 km2 in 2017-18. On the CPNM, kit fox population dynamics and ecology appear to be primarily influenced by kangaroo rat abundance and not by competition from coyotes. Consequently, kit fox populations appear to be regulated by “bottom up” processes.