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Swift Fox Symposium

Scent-station Survey Methods for Swift and Kit Foxes

Glen A. Sargeant1, Patrick J. White2, Marsha A. Sovada1, and Brian L. Cypher3. 1Northern Prairie Wildlife Research Center, US Geological Survey, Jamestown, ND 58401. 2California Polytechnic State University, San Luis Obispo, CA 93407. 3Endangered Species Program, Naval Petroleum Reserves in California, P.O. Box 9622, Bakersfield, CA 93309.

We compared scent-station survey techniques for monitoring the distribution and relative abundance of swift (Vulpes velox) and kit (Vulpes macrotis) foxes. We used data collected in Sherman and Wallace counties, Kansas, during 1996 (swift fox); at Camp Roberts, California, during 1988-97 (kit fox); and at the U.S. Department of Energy's Naval Petroleum Reserves, California, during 1984-96 (kit fox). Principal findings and recommendations are as follows: 1) Scent-stations were not a cost-effective method for determining the distribution of swift fox in Kansas, but may be useful for monitoring population trends. 2) In Kansas, monthly visitation rates declined from April-August, then increased 8-fold in October when subadults began visiting stations. 3) Spring and summer surveys, but not autumn surveys, detected a sustained decline in the kit fox population at Camp Roberts. Autumn visitation rates may not be a reliable population index because subadults are responsible for most visits and juvenile recruitment is strongly influenced by factors other than population density. Spring and summer surveys may therefore be more appropriate than autumn surveys. 4) In Kansas, visits were more frequent on the first night of each monthly survey than on subsequent nights due to habituation. 5) Repeated operation of stations yielded less information about abundance than could have been obtained by establishing new stations. Habituation and individual differences in detectability reduce benefits of checking the same stations on >1 day in succession or on >1 survey occasion annually. 6) Kit foxes readily visited stations baited with fatty acid scent (FAS) although coyotes (Canis latrans) were the principal source of kit fox mortality in our study areas. 7) In Kansas, swift foxes visited stations with a sand-and-mineral oil substrate 2.4 times as frequently as track plates. The use of track plates to facilitate track identifications may negate efforts (e.g., choice of lures) to increase visitation rates. Our results suggest intuitive perceptions of scent-station methods are frequently incorrect and emphasize the need for objective, experimental comparisons of methods.

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