MOOSE AND DEER POPULATION TRENDS IN NORTHWESTERN ONTARIO: A CASE HISTORY

Abstract

Many interrelated factors contribute to the rise and fall of white-tailed deer (Odocoileus virginianus) and moose (Alces alces) populations in the mixed boreal forests of eastern North America where these species often cohabit. A question not satisfactorily answered is why do moose populations periodically decline in a pronounced and prolonged way while deer populations continue to do well during times when habitat conditions appear good for both? Long-term historical data from the Kenora District of northwestern Ontario, Canada provided an opportunity to better understand temporal relationships between trends in deer and moose numbers and landscape-level habitat disturbances, ensuing forest succession, climate, predators, and disease. Over the past 100 years, moose and deer have fluctuated through 2 high-low population cycles. Deer numbers were high and moose numbers were low in the 1940s and 50s following a spruce budworm (Choristoneura fumiferana) outbreak. By the early 1960s, deer trended downwards and remained low during an extended period with frequent deep-snow winters; as deer declined, moose recovery was evident. Moose increased through the 1980s and 1990s as did deer, apparently in response to considerable habitat disturbance, including another spruce budworm outbreak and easier winters. However, despite conditions that were favourable for both species, moose declined markedly beginning in the late 1990s, and by 2012 were at very low levels district-wide while deer numbers remained high. Despite the moose decline being coincident with a short-lived winter tick (Dermacentor albipictus) epizootic in the early 2000s and increasing numbers of wolves (Canis lupus), we argue that the meningeal worm (Parelaphostrongylus tenuis) likely played a major role in this moose decline.