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Abstract

U.S. Fish and Wildlife Service staff at Hart Mountain National Antelope Refuge (HMNAR), southeastern Oregon, documented high pronghorn (Antilocapra americana) fawn mortality, subsequent low fawn recruitment, and declining pronghorn numbers from 1996 to 1999. Coyote (Canis latrans) predation was the primary cause, accounting for 60–85% of fawn mortalities each year, and fawns were not physiologically predisposed to predation. Therefore, we investigated certain coyote population parameters (age structure, survival, density, physiology) to evaluate how or if these factors influence coyote predation rates on pronghorn fawns. We captured 11 coyotes (5 male and 6 female) in December 1998. Age of captured animals ranged from 1.7 to 10.7 yrs (x̄ = 5.0 years), and all coyotes appeared healthy upon capture. There were no known mortalities through December 1999. We estimated pre-whelping (December through February 1997–1999) density from howling surveys conducted within HMNAR to be 0.40–0.53 km−2. Compared to other published studies, we found significant (P ≤ 0.05) differences in selected blood parameters (e.g., blood urea nitrogen, total protein, white blood cell counts), indicating coyote nutrition may be marginal to deficient during winter at HMNAR. A high percentage of coyotes (91%) tested positive for serum-neutralizing antibodies to canine parvovirus. We judged that parasite (Toxascaris spp., Alaria spp., Sarcocystis spp., and Isospora spp.) prevalence and intensity were not high enough to influence coyote condition. Based on our data, the coyote population at HMNAR is old aged, at a relatively high density, and stable, but their nutrition may be marginal to deficient during winter. Presently, we are unable to draw direct conclusions relating the parameters we sampled with predation rates by this unexploited coyote population.

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