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Changes among Caribou (Rangifer tarandus) in Slate Islands Provincial Park following successive arrivals of Gray Wolves (Canis lupus)

Abstract:

From observations of Caribou (Rangifer tarandus) during 1974-2017 on the Lake Superior archipelago that makes up Slate Islands Provincial Park, we infer direct and indirect effects of the arrival of Gray Wolves (Canis lupus) in the winters of 1993-1994, 2002-2003, and 2013-2014. Arrivals consisted of wolf pairs in the first and third cases, and, in each instance, wolves survived at least one additional winter. Wolves created conditions that led to behavioural changes in Caribou consistent with avoiding predators. Caribou did not frequent calving locations near shoreline areas, nor did they use water to escape from wolves. Wolves occupied a Red Fox (Vulpes vulpes) den, and its general location, at one time frequented by Caribou, became the most common area to find Caribou carcasses and was avoided by Caribou when wolves were present. Caribou were functionally extirpated by wolves, with just two to four males remaining in 2017. Wolves also appear to have caused extirpation of American Beaver (Castor canadensis) and Red Fox from the archipelago, while Snowshoe Hare (Lepus americanus) populations were unaffected by wolves.