Abstract

I examined the relationship between age, body size and fecundity in 833 female moose (Alces alces) from 14 populations in Sweden sampled during 1989-1992. Data on population density food availability and climatic conditions were also collected for each population. Age and body mass were both significantly positively related to fecundity, measured as ovulation rate, among female moose. The relationship between the probability of ovulation and body mass was dependent on age with (1) a higher body mass needed in younger females for attaining a given fecundity, and (2) body mass having a stronger effect on fecundity in yearling (1.5 year) than in older (greater than or equal to 2.5 year) females. Thus, a 40 kg increase in yearling body mass resulted in a 42% increase in the probability of ovulation as compared to a 6% increase in older females. The lower reproductive ef fort per unit body mass, and the relatively stronger association between fecundity and body mass in young female moose compared to older ones, is likely to primarily represent a mechanism that trades off early maturation against further growth, indicating a higher cost of reproduction in young animals. In addition to age and body mass, population identity explained a significant amount of the individual variation in fecundity, showing that the relationship between body mass and fecundity was variable among populations. This variation was in turn related to the environment, in terms of climatic conditions forcing female moose living in relatively harsh/more seasonal climatic conditions to attain a 22% higher body mass to achive the same probability of multiple ovulation (twinning) as females living in climatically milder/less seasonal environments. The results suggests that the lower fecundity per unit body mass in female moose living in climatically harsh/more seasonal environments may be an adaptive response to lower rates of juvenile survival, compared to females experiencing relatively milder/less seasonal climatic conditions.

Keywords

fecundity; body size; climate; survival; adaptation

Published in

Oecologia
1996, Volume: 106, number: 2, pages: 212-220
Publisher: SPRINGER VERLAG

SLU Authors

• Sand, Håkan

  • Department of Wildlife Ecology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Ecology
Zoology


Publication identifier

DOI: https://doi.org/10.1007/BF00328601

Permanent link to this page (URI)

https://res.slu.se/id/publ/51315