Potential habitat and carrying capacity of endangered San Joaquin kit foxes in an urban environment: implications for conservation and recovery

Abstract

The San Joaquin kit fox (Vulpes macrotis mutica; SJKF) is federally endangered due to profound habitat loss. A population of SJKF occurs in the urban environment in the city of Bakersfield, California, and may be important for SJKF conservation. We conducted a systematic survey using automated camera stations and occupancy analysis to identify suitable habitat for SJKF in Bakersfield and to estimate a conceptual carrying capacity in the urban environment. We identified high, medium, and low suitability habitat totaling 121 km2, 196 km2, and 40 km2, respectively. Based on a mean urban kit fox home range size of 0.78 km2 and an assumption of two adults in high suitability home ranges and one adult in medium suitability ranges, we estimated the adult carrying capacity in Bakersfield to be 561 foxes. This estimate seems plausible as the number of adult SJKF in Bakersfield was estimated to be 381 in 2015, and the number of foxes already had been reduced by a sarcoptic mange epidemic that began two years earlier. A carrying capacity of 561 adults would increase the estimated range-wide carrying capacity by as much as 38%. Adult density estimates derived for the urban SJKF population based on the carrying capacity (1.57/km2) and home range size (2.56/km2) were higher than estimates for foxes in natural habitats. The urban SJKF population in Bakersfield is substantial and therefore could contribute significantly to conservation and recovery efforts for SJKF. Given our results, a potential conservation strategy may be to encourage or even establish additional urban SJKF populations.