DEMOGRAPHIC STATUS OF MOOSE POPULATIONS IN THE BOREAL PLAIN ECOZONE OF CANADA

Abstract

Broad scale analyses of winter population survey data collected between 1985 and 2015 were conducted to provide a synthesis of the current status and historical performance of 14 moose (Alces alces) populations residing in the Boreal Plain Ecozone of Saskatchewan and western Manitoba. Population time series models indicated a broad scale decline averaging 30% in moose populations across the Boreal Plain Ecozone since 2000 relative to the long-term (1985 to 2015) cumulative mean population size. Demographic patterns and rates of population change were variable among and within populations across years. We found an inverse relationship between adult sex ratio (bull:cow) and population density (R² = 0.48, P < 0.001), which suggests negative population growth (λ < 1.0) when the adult sex ratio falls below a density-dependent threshold for population growth. Winter calf recruitment (calves/cow) was positively correlated (R² = 0.12, P = 0.027) with adult sex ratio. Stable or increasing populations (λ ≥ 1.0) tended to have lower adult sex ratios relative to winter calf recruitment ratios than declining populations. Population state and vital rate relationships are useful to assess population performance and guide science-based moose management strategies in a Management-by-Objective decision-analytic framework.