Using a species distribution model to evaluate habitat occupancy by the native Sacramento Valley red fox

Background/Question/Methods

The Sacramento Valley red fox (Vulpes vulpes patwin) is a subspecies of red fox endemic to the northern portion of California’s Central Valley, and is currently under consideration as a California Species of Special Concern. Loss of grassland habitat has reduced its distribution and abundance since historical times. It is not known if the current population occupies all potentially suitable habitat. Therefore, we sought to assess occupancy of predicted habitat. We used an existing species distribution model based on Maxent analysis of presence-data from 2007–2009 to guide our current survey (2013–present). We used a stratified random design to select a combination of survey sites in predicted-presence (n = 13) and predicted-absence (n =4) habitats. To control for imperfect detection probabilities, we also utilized positive-control sites (n = 3) in locations where red foxes were known a priori to occur. We then employed remote camera surveys and noninvasive genetic sampling of hair and scat samples to determine red fox presence at survey sites. 

Results/Conclusions

Our preliminary findings were as follows: detections of red fox in all 3 positive control sites, none of the predicted-absence sites, and 1 of 7 (completed) predicted presence sites. We present details associated with these results, along with those for the 6 remaining predicted-presence sites, to be completed by April 2014.