Abstract

Topic: Moose management and monitoring

Assessing drivers of 20 years of population decline in Ontario’s moose

Joseph M. Northrup¹, Brent Patterson², Robby Marrotte², Mike Brown², Nick Luymes², Tyler Wheeldon², Eric Howe², Phil Dewitt², Dani Freund³, Alex Bezzina³, Stephen Sucharzewski²

Ontario Ministry of Natural Resources, 2140 East Bank Dr., Peterborough, Ontario, Canada
Ontario Ministry of Natural Resources
Trent University

Abstract
The moose population in Ontario, Canada, has declined by approximately 20 percent since the early 2000s, with local declines exceeding 50% in some areas. Numerous mechanisms have been hypothesized to drive this decline, including over-harvest, changes in habitat with declines in forestry activities, parasite impacts and predators. We aimed to better understand the potential drivers of population decline across the province, while designing a comprehensive field research program to obtain mechanistic understanding of drivers. Using >20 years of aerial survey data, combined with licensed hunter surveys, we assessed putative drivers of population change in moose across most of their distribution in Ontario (an area spanning > 500,000 km2). We found that hunter harvest and wolf predation were likely causes of population decline in some areas, with the potential for predation now acting as a regulating factor and keeping moose populations well below carrying capacity. Predation appeared to act in a density dependent manner, heavily influencing populations at low moose density but having little effect at high density. Predation, hunter harvest and climate also influenced calf recruitment, with areas of more severe winters, higher hunter harvest and greater relative wolf activity seeing lower recruitment. Although these findings provide important insight into potential drivers of moose population decline, more detailed field study is needed to develop the mechanistic understanding require to implement management actions to recover moose populations. We will discuss how these findings are directing the implementation of a multi-year field study aimed at assessing moose population decline and the interaction between, moose, wolves, American black bears, white-tailed deer and people.