Opposite responses of body condition and fertility in adjacent moose populations

Abstract

ABSTRACTMoose (Alces alces) populations exceed 3 individuals/km2 in some wildlife reserves and parks of northeastern Canada. Heavy browsing pressure at such densities is potentially altering the ecological integrity of forests with eventual negative consequences for moose. We hypothesized that regulation by resources would be limited by the capacity of female moose to modulate their reproductive strategies to maintain high fertility despite a decline in body condition. We observed a 20–33% decline in rump fat thickness in males and females, respectively, from the high density Matane Wildlife Reserve in Eastern Québec in October compared to an adjacent population. We also observed a lower mass of the peroneus group of muscles for males (−3%) and prime‐aged females (−8%) in the Matane Wildlife Reserve than in the adjacent population. Females from the Matane Wildlife Reserve population had a lower twinning ovulation rate (1 out of 20 vs. 7 out of 21 ovulating females in the adjacent population) but >15% higher overall ovulation rate. Our results suggest that female moose can maintain high fertility despite a decline in body condition, by reducing their litter size at ovulation and conserving energy to increase the probability of annual reproduction. The adjustment of female reproductive strategies illustrates the plasticity of moose in response to decreasing habitat quality. We conclude that in the absence of specialist predators, equilibrium with forage is unlikely for large herbivores in the short or mid‐term. Active management of moose populations is likely required to maintain the ecological integrity of boreal forests. © 2014 The Wildlife Society.