Reproduction of the San Joaquin kit fox (Vulpes velox macrotis) at Camp Roberts Army National Guard Training Site, California

by: Kenneth A. Spencer, William H. Berry, William G. Standley, and Thomas P. O'Farrell

ABSTRACT: The reproduction of a San Joaquin kit fox population (Vulpes velox macrotis) was investigated at Camp Roberts Army National Guard Training Site, California, from November 1988 through September 1991. Of 38 vixens radiocollared prior to parturition, 12 (32%) were successful in raising pups from conception to a point where pups were observed above ground. No yearling vixens were known to be reproductively active. The mean litter size during 1989 - 1991 was 3.0 (n = 21, SE = 0.28) and ranged from one to six pups. Both the proportion of vixens successfully raising pups and the mean litter size observed at Camp Roberts during this study were lower than those reported at other locations. Sex ratios of kit fox pups were male biased two of the threee years, but did not differ statistically from 1:1 throughout the study. Whelping was estimated to occur between February 15 and March 5. Results of this study support previous reports that kit foxes are primarily monogamous, although one case of polygamy may have occurred. Both the proportion of dispersing radiocollared juveniles (26%) and the mean dispersal distance (5.9 km) of juveniles at Camp Roberts appeared low compared to other locations.

1992. U. S. Dept. of Energy Topical Report, EG&G/EM Santa Barbara Operations Report No. EGG 10617-2154. 18 pp. Reprints are available from the National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Road, Springfield, VA 22161.

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