DOES UNBALANCED SEX RATIO IN ADULT MOOSE AFFECT CALF SIZE IN THE FALL?

It has been suggested that the sex ratio should be close to parity among adult moose to ensure high productivity. When the sex ratio is female biased, the mating period may extend over 2 - 3 estrus cycles and the calving period is delayed. As a result, some calves may be smaller in the fall and less likely to survive over winter. The objective of this study was to test whether an unbalanced adult moose sex ratio affects calf size in the fall. To do so, 8 hunting zones were sampled out of 24 in the province of Québec; their sex ratio among adults was based on aerial surveys. ANOVAs were conducted on 3 body measurements (head width, left ear, and hind foot lengths) on calves collected in the fall by hunters between 1995 and 1997 to compare body measurements from zones with different adult sex ratios. Our results showed that 2 of the measures were positively related to the percentage of males among adults. Consequently, we cannot reject the hypothesis that calves are smaller in the fall when adult sex ratio is unbalanced. However, differences were very small. Assuming that such events occur, we suggest that the impact is weak at the population level, unless affected calves are least likely to survive until fall. However, the productivity (estimated in winter) in the various hunting zones of Québec is not related to the adult sex ratio. Thus, out results indicate that it is not necessary to consider this potential impact in the management of moose populations under the current range of sex ratios observed