Mountain goat recruitment: kid production and survival to breeding age

During a 5-year study of a marked population of mountain goats (Oreamnos americanus) in west-central Alberta, 5 of 17 females produced their first kid at 4 years of age, while most females did not reproduce until 5 years of age. Twinning accounted for 2% of births. Survival of kids to 1 year averaged 60%, and survival of females from 1 to 4 years of age was 52%. Most deaths of kids occurred in September–November and appeared due to predation by wolves (Canis lupus), cougars (Felis concolor), and grizzly bears (Ursus arctos). At least half of the yearlings lost from the population were preyed upon, but losses of 2-year-olds were concentrated in the summer, suggesting emigration. Survival rates of young goats were not different according to sex. We suggest that nutrient availability limits the reproductive performance of the goats by retarding their growth, while predation on young goats is a major source of mortality.