Evaluation of Survey Methods and Development of Species Distribution Models for Kit Foxes in the Great Basin Desert

Abstract

Historically, kit foxes (Vulpes macrotis) once occupied the desert and semi-arid regions of southwestern North America, ranging from Idaho to central Mexico. Once the most abundant carnivore in the western desert, the species is now considered rare. Survey methods have been evaluated for kit foxes, but often in populations where abundance is high and there is little consensus on which technique is best to monitor abundance. We conducted a 2 year study to evaluate 4 methods suggested to be best for detecting kit foxes and examined the detection rates relative to minimum kit fox abundance (determined by radio-collared animals). The study was conducted on the U.S. Army Dugway Proving Grounds and the bordering BLM lands in Utah. We evaluated scat deposition surveys, scent station surveys, spotlight survey, and trapping. All surveys were conducted on 15 5-km transects during the three biological seasons of the kit fox. Home range sizes for kit foxes on the study site were extremely large, averaging 20.5 km 2 . Scat deposition surveys had both the highest detection probabilities ( = 0.88) and were most closely related to minimum known fox abundance (r 2 = 0.50, P = 0.001). The next best method for kit fox detection was the scent station survey ( = 0.73), which had the second highest correlation to fox abundance (r 2 = 0.46, P < 0.001). For detecting kit foxes in a low density population we suggest using scat deposition transects during the breeding season. This method had both the highest detection probability and correlation 11 to kit fox abundance. Scat deposition surveys have low costs, resilience to weather, low labor requirements, and pose no risk to the study animals. The breeding season was ideal for monitoring kit fox population size, as detections consisted of primarily the resident population and we had the highest detection probabilities during this season. In areas with sympatric canids, careful training of technicians may be required, but risk of overlapping scat dimensions should be lowest during the breeding season as most sympatric canids are also fully grown by the subsequent breeding season.