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29th Annual Meeting and Symposium of the
Desert Tortoise Council, February 20-23, 2004
Abstracts
The Scenting Abilities of Detector Dogs for Desert Tortoise Surveys: Pilot Study Results
Curtis D. Bjurlin1, William J. Vanherweg1, Paula
Mackay2, Robert Long3, Stephen Weigley4,
and Barbara Davenport4
1Wildlife Detector Dogs, 2510 4th Street, Bakersfield CA 93304
2Consulting Biologist, 716 Shaker Hill Road, Starksboro, VT 05487
3Vermont Cooperative Fish & Wildlife Research Unit, 212 Aiken
Center, University of Vermont, Burlington, VT 05405
4Pack Leader Dog Training, 14401 Crews Rd. KPN, Gig Harbor, WA
98329
Desert tortoises and their sign can be notoriously difficult to census, especially at low population densities and in thick vegetation or rough terrain. In October, 2003 we conducted a pilot study to systematically evaluate the tortoise detection abilities of two professional detector dogs. Dog scenting ability is well documented in law-enforcement and these skills have been previously applied to other wildlife species. Work was conducted at the Lokern Natural Area in the southern San Joaquin Valley. Lokern is an Atriplex shrubland on sandy loam soils that receives about 6 inches of rain annually making it a good model of the Mojave desert. However, tortoises do not naturally occur at the site, allowing us to experimentally manipulate densities using captive animals. We deployed 13 adult tortoises, 8 subadults, and 13 yearlings over a series of 9 trials at fenced ten-acre plots. Survey teams (one dog working off-leash, one handler, and one navigator) conducted a single coverage of each plot at a 50m transect interval. Both dogs were 100% successful at locating adult and subadult tortoises, even those hidden in dense vegetation or burrows. Moreover, the dogs detected 28-50% of yearling tortoises that were buried underground in artificial burrows. These data suggest that detection dogs may greatly enhance tortoise population surveys and construction clearance activities, especially with regards to small tortoises that typically go undetected.
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