Harvest of female moose at high density: modelling the impacts of harvest on population size and biomass yield

Management of harvested moose Alces alces populations at or above ecological carry capacity risks habitat degradation, nutritional limitation, and increased population vulnerability during severe winters. Selective female harvests have the potential to curb population growth while providing hunting opportunities. Using a female‐only, stage‐structured population model parameterized from an Interior Alaska moose population, we examined numbers of harvested individuals and biomass yield associated with reducing a population from 14 500 to 10 000 individuals over 3, 5 and 8 years. We compared harvest of cow—calf pairs versus unaccompanied females. The higher potential for adult female survival compared with calf survival to impact population growth rate resulted in higher yields from cow—calf harvests. Achieving the population objective required the mean annual harvest of 889, 626 and 477 cow—calf pairs or 1161, 805 and 605 unaccompanied females, for the three harvest durations, respectively. Over a five‐year period, cow—calf harvests yielded approximately 56% more individuals and 17% greater biomass, an estimated difference of 130 metric tonnes. The two harvest scenarios resulted in similar stage distributions and population growth rates following the termination of harvest. While the cow—calf harvests can provide higher yields, they also require substantially higher hunter effort to achieve population objectives. The harvest of unaccompanied females will result in greater population reduction per individual harvested and will therefore be the preferable strategy when hunter effort is limited. In addition, the large harvest numbers necessary to achieve the modelled management goal, suggest that some moose populations may escape the range where they can be easily be controlled through female harvest, especially when harvest is limited by hunter interest or access.