Finding a fox: an evaluation of survey methods to estimate abundance of a small desert carnivore

PLoS One. 2014 Aug 22;9(8):e105873. doi: 10.1371/journal.pone.0105873. eCollection 2014.

Abstract

The status of many carnivore species is a growing concern for wildlife agencies, conservation organizations, and the general public. Historically, kit foxes (Vulpes macrotis) were classified as abundant and distributed in the desert and semi-arid regions of southwestern North America, but is now considered rare throughout its range. 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 four survey methods (scat deposition surveys, scent station surveys, spotlight survey, and trapping) for detecting kit foxes and measuring fox abundance. We determined the probability of detection for each method, and examined the correlation between the relative abundance as estimated by each survey method and the known minimum kit fox abundance as determined by radio-collared animals. All surveys were conducted on 15 5-km transects during the 3 biological seasons of the kit fox. Scat deposition surveys had both the highest detection probabilities (p = 0.88) and were most closely related to minimum known fox abundance (r2 = 0.50, P = 0.001). The next best method for kit fox detection was the scent station survey (p = 0.73), which had the second highest correlation to fox abundance (r2 = 0.46, P<0.001). For detecting kit foxes in a low density population we suggest using scat deposition transects during the breeding season. 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 the resident population and had the highest detection probabilities. Using appropriate monitoring techniques will be critical for future conservation actions for this rare desert carnivore.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Costs and Cost Analysis
  • Environmental Monitoring / economics
  • Environmental Monitoring / methods*
  • Feces
  • Female
  • Foxes*
  • Male
  • Population Density*
  • Telemetry
  • Utah

Grants and funding

Funding and logistical support were provided by the Department of Defense, United States Army Dugway Proving Ground, Environmental Programs, Dugway, Utah, and the United States Department of Agriculture, Wildlife Services, National Wildlife Research Center, Utah State University, Logan, Utah. Additional funding was provided by the Quinney College of Natural Resources, Utah State University, Logan, Utah, and the Endangered Species Mitigation Fund of the Utah Department of Natural Resources, Division of Wildlife Resources, Salt Lake City, Utah. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.