Spring-Fall Calf Mortality in an Alaska Moose Population

Abstract

Calf mortality was studied in a population of moose (Alces alces) near Palmer, south-central Alaska, from May through October, 1965. During this period, the number of calves per 100 cows decreased from 84.3 to 36.2, suggesting a spring-fall calf mortality of more than 50 percent. Drowning, entrapment by vegetation, abandonment, injury inflicted by the dam, and predation by brown bears (Ursus arctos) were observed causes of calf mortality. Exclusive of hunting deaths, the major mortality of Alaska moose occurs during the first year of life. Thus recruitment at the yearling level is often less than half the potential delivered at calving the previous spring (Alaska Department of Fish and Game, unpublished files). Logically, harsh winters account for some mortality; yet, in an average year, the moose calf is perhaps most vulnerable to the environment during its infancy-the first spring, summer, and fall of its life-when it is still very small and relatively weak. This paper reports an assessment of the magnitude and nature of calf mortality during this period in a small population. I am grateful to Robert A. Rausch and Arthur E. Bratlie for advice and assistance