Last updated: March 31, 2023
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Climate Change at Isle Royale: Winter Tick
The winter tick, or moose tick, is a Northwoods pest that feeds on members of the deer family. On Isle Royale, moose are heavily afflicted with the parasite. Though winter ticks are not interested in humans, they have a profound effect on the island’s ecosystem.
Lindsey Welch
Impact on Moose
Winter ticks emerge from their eggs each fall in search of a host. After attaching to a moose, female ticks take blood meals through the winter before dropping off each spring to lay eggs in the soil.
In years when ticks are abundant, there can be as many as 100,000 feeding on a single moose. To relieve the skin irritation caused by a tick infestation, moose scratch and scratch, spending more time trying to rid themselves of the pest than foraging for already scare food sources. This exacerbates winter malnourishment. Excessive itching also adversely affects the moose’s fur coat, causing hairloss, and stressing the cold-loving creatures. A severe tick infestation can also lead to significant blood loss, which can be fatal for the host. The negative effects of winter ticks on Isle Royale moose are severe - more moose are lost to ticks each winter than to predation from wolves.
Though the blood loss, malnourishment, and spotty coats are serious problems for moose, the tick thrives.
Climate Concerns
Unlike other tick species, winter ticks hunt in packs. Larvae gather strategically in interlocking clumps on vegetation. When one tick snags a passing victim, hundreds or thousands more could come along for the ride. Snow or cold has potential to kill this larvae – but as snow and cold arrive later and later in the fall, ticks have more time to find a host. Thus, winters that are shorter and warmer have been shown to correlate with increased numbers of ticks in moose populations. Additionally, warmer temperatures during the spring, summer, and fall are linked to higher reproductive success and greater survival for winter ticks.