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Twenty-Fourth Annual Meeting and Symposium of the
Desert Tortoise Council, March 5-8, 1999
Abstracts
STUDENT PAPER
Home Range and Movements of Hillside Residing Desert Tortoises
in the Western Mojave Desert
Ty J. Gardner
Department of Biology, Utah State University, Logan, UT 84322-5305
Tortoises were tracked during the 1997 and 1998 field seasons, at two hillside sites within the Western Mojave Recovery Unit: The Barstow Marine Corps Logistical Base Rifle Range (Barstow) and The Marine Corps Air Ground Combat Center Lava Range (Lava). All fixes at each site were combined to estimate a search area, allowing for estimation of density in tortoises/mi2 (Barstow = 60.8 - 76.5, Lava = 14.1 - 17.7). Home range size was not correlated with tortoise density.
Fixes within each year were used to calculate home range size, overlap, and interfix distances. Barstow minimum convex polygon (MCP) home ranges (n=19) were significantly larger (P< 0.001) in 1998 (8.46 ha ± 5.22) than in 1977 (3.62 ha ± 3.12). No difference was found between males (n=10) and females (n=9) at Barstow in either year. Lava MCP ranges (n=5) were larger in 1998 (21.59 ha ± 36.24) than in 1997 (8.39 ha ± 10.95), but not significantly so. The larger 1998 ranges overlapped a large portion of the range used by the same animal in 1997 at both Barstow (83.3% ± 16.07) and Lava (81.9% ± 18.43), but the 1997 ranges included only a small portion of the same animal’s 1998 range (Barstow: 38.1 ha ± 25.4; Lava: 46.24 ha ± 21.01).
Barstow mean inter-fix distances were significantly larger (P<0.001) in 1998 (117.5 ha ± 39.6) than in 1997 (72.2 ha ± 38.8); however, distances in maximum inter-fix distances (1998 = 360.5 ha ± 114.8; 1997 = 288.4 ha ± 149.5) were marginally significant (P = 0.052). Lava mean and maximum inter-fix distances for 1998 (262.8 ha ± 234.0; 897.2 ha ± 379.4) were not significantly different from those for 1997 (160.5 ha ± 120.5; 469.8 ha ± 332.6).
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