A population of feral horses (Equus caballus) was studied from 1986 to 1991 to determine the demographic impact of predation by the mountain lion (Felis concolor). The population, inhabiting a 600-km2 area on the central California – Nevada border comprised approximately 162 individuals > 1 year old, with an average of 9 yearlings, 8 two-year-olds, and 144 adults. Numbers of horses varied by only 4–8% and showed no consistent trend. The parturition peak spanned May and June, when 80% of foaling occurred. One-third of the average annual cohort of 33 foals was missing by July and only half of the cohort remained by October. The mean first-year survival rate estimated from the differential incidence of foals and yearlings in successive years was 0.27, which was less than one-third of the foal survival rate reported for other feral horse populations. A minimum of four adult mountain lions used the study area each year between May and October. Of 28 foal carcasses located from May to mid-July, at least 82% were the result of mountain lion kills. No evidence of predation on older horses was observed, but mountain lions preyed on mule deer (Odocoileus hemionus) during winter. We conclude that the growth of this horse population is limited by predation.
- Wolfe, Michael L.
- Kirkpatrick, Jay F.
- CANADIAN JOURNAL OF ZOOLOGY Journal
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