ARE MOOSE ONLY A LARGE DEER?: SOME LIFE HISTORY CONSIDERATIONS

Abstract

Body mass generally accounts for a large part of variation in life history traits of ungulates. However, phylogeny and ecological features such as habitat or diet have been shown to cause differences in life history patterns among species of similar size. To assess the factors that shape life history traits of moose (Alces alces), the largest deer (Cervidae) species, I fitted allometric relationships among ungulate species for a set of life history traits. I compared moose life history traits first with both traits expected from allometric equations and traits of similar-sized bovids. Both kinds of analyses led to the same results. While moose calves grow as expected from the size of their mothers, they start life at only about half the expected size. Moose populations have higher growth rates and shorter generation times as compared to similar-sized ungulates. Females reproduce earlier and have larger litters relative to their body size. The resulting faster than expected life cycle for moose cannot be accounted for by changes in survival patterns: moose closely fit the general pattern of ungulate population dynamics characterized by a low and variable juvenile survival as opposed to a high and constant survival of prime-age females. High reproductive output accounts for the fast life cycle of moose populations compared to other similar-sized ungulates. I propose that the high reproductive output has evolved in response to the unpredictable environmental conditions of early successional habitats preferred by moose. The evolutionary strategy of moose appears more similar to that of a very large roe deer (Capreolus capreolus) than that associated with larger deer in general.