Table of Contents
ISRN Zoology
Volume 2012, Article ID 197356, 8 pages
http://dx.doi.org/10.5402/2012/197356
Research Article

Swift Foxes and Ideal Free Distribution: Relative Influence of Vegetation and Rodent Prey Base on Swift Fox Survival, Density, and Home Range Size

1Department of Wildland Resources, Utah State University, Logan, UT 84322, USA
2Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture, Fresno, CA 93710, USA
3National Wildlife Research Center, Wildlife Services, U.S. Department of Agriculture, Logan, UT 84322, USA

Received 23 April 2012; Accepted 16 May 2012

Academic Editors: A. Arslan and A. Ramirez-Bautista

Copyright © 2012 Craig M. Thompson and Eric M. Gese. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Swift foxes (Vulpes velox) are an endemic mesocarnivore of North America subject to resource and predation-based pressures. While swift fox demographics have been documented, there is little information on the importance of top-down versus bottom-up pressures or the effect of landscape heterogeneity. Using a consumable resource-based ideal free distribution model as a conceptual framework, we isolated the effects of resource-based habitat selection on fox population ecology. We hypothesized if swift fox ecology is predominantly resource dependant, distribution, survival, and space use would match predictions made under ideal free distribution theory. We monitored survival and home range use of 47 swift foxes in southeastern Colorado from 2001 to 2004. Annual home range size was 15.4 km2, and seasonal home range size was 10.1 km2. At the individual level, annual home range size was unrelated to survival. Estimates of fox density ranged from 0.03 to 0.18 foxes/km2. Seasonal survival rates were 0.73 and 1.0 and did not differ seasonally. Foxes conformed to the predictions of the ideal free distribution model during winter, indicating foxes are food stressed and their behavior governed by resource acquisition. During the rest of the year, behavior was not resource driven and was governed by security from intraguild predation.