Friday, December 14, 2018

As Winters Warm, Blood-Sucking Ticks Drain Moose Dry

By Laura Poppick on December 11, 2018

Moose numbers have declined roughly 10 percent in Maine and as much as 50 percent in New Hampshire since the early 2000s; Kantar and his colleagues in New England attribute this largely to a climate change–linked explosion in winter tick populations. In a recent Canadian Journal of Zoology study they report three consecutive years of tick epizootics (epidemics among animals of the same species) from 2014 through 2016—a run they say is unprecedented in this region. The ticks have become so voracious in some places a single moose can carry an appalling 90,000 at once, they report. In such numbers the ticks drain so much blood that the host moose can become anemic and malnourished and “can’t replace the blood fast enough,” Kantar says. In the case of many first-year calves like the one Kantar responded to in April, they die.


ticks “quest” (search for hosts) in the fall and stop once freezing temperatures settle in. As winter continues to arrive later everywhere, the time window for moose to pick up ticks stays open longer, Kantar notes.

Increasingly warmer and snow-free springs also mean female ticks that fall off their hosts can more easily survive to lay nests of larvae that emerge in the fall, says Helen Schwantje, a veterinarian for British Columbia’s Ministry of Forests, Lands, Natural Resource Operations Wildlife Management. The resulting decline in moose populations leaves holes in the cultural landscape as well as the ecological one, Schwantje says. “They have huge cultural and nutritional value to our First Nations,” she says. And when moose forage in wetlands, they help release nutrients into the environment and make them available to other plants and organisms, studies have shown.

Schwantje says the worrying growth of winter tick infestations in British Columbia has now spread to populations of boreal caribou—an alarming sign the ticks are infiltrating species and ranges they have not significantly occupied in the past. Boreal caribou are already listed as a threatened species, and the increased threat of ticks is “just one more thing they have to deal with,” Schwantje says.


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