Effects of intensive harvesting on moose reproduction

Abstract

1. It has been hypothesized that a balanced adult sex ratio is necessary for the full participation of ungulate females in reproduction and therefore high productivity. We tested this general hypothesis by combining two complimentary approaches. 2. First, using telemetry (n=60) and annual aerial censuses between 1995 and 1998, we compared two moose Alces alces populations in Quebec, Canada, one non-harvested and the other subject to intensive sport harvesting from the end of September to mid-October. We tested the following predictions for the harvested population: (i) females increase movements and home ranges during the mating period; (ii) the mating system is modified, with the appearance of groups of one male and many females; (iii) subadult males participate in reproduction; (iv) the mating period extends over two to three oestrus cycles; (v) the calving period extends over several months; and (vi) productivity declines. 3. Daily movements and home range sizes during the mating period did not differ between harvested and non-harvested populations. Most groups observed were male female pairs. Subadult males (1.5-2.5 years old) were only observed with females in the harvested population. Mating and calving periods did not differ between populations. The proportion of females that gave birth and the number of calves produced were also comparable in the two populations. 4. Secondly, we also assessed the existence of a relationship between population productivity and percentage of males in various management units of the province of Quebec that were characterized by a wide range in sex ratios. Contrary to prediction (vi), the number of calves per 100 adult females was not related to the percentage of adult males in the population. 5. The participation of young adult males (subadults) in reproduction in our harvested population may have compensated for the lower percentage of adult males, and thus productivity was unaffected. We therefore reject the hypothesis that intensive harvesting, at least at the level we observed, affects reproduction and population productivity. 6. As there are some uncertainties regarding the long-term effects of high hunting pressure, however, managers should favour sex ratios close to levels observed in non-harvested populations.