Like many New Englanders, moose aren’t particularly good at personal grooming. (I can say that because I’m a Mainer!) While deer and elk groom off winter ticks, moose do not, so moose are spending their winters covered in tens of thousands of engorged ticks. These tick populations consume an astounding volume of blood, so calves and even adult moose are being effectively sucked dry.
To give the moose some credit, they do try to groom off their ticks by scratching and biting their own fur, rubbing on trees, etc. Those behaviors aren’t effective at tick removal, though, and instead the moose end up rubbing off their dark outer hairs, leaving behind just their pale, broken hair shafts and bald patches. As a result, “Ghost Moose” are running around New England forests in freezing winter temperatures wearing nothing but their skivvies, trying vainly to produce enough blood to keep their own machinery running.
We’d expect to find that are these tick-infested moose are dying, and that appears to be the case. Estimating moose population sizes is not particularly easy, but it looks like New England moose populations are declining in some states. Additionally, scientists have found high mortality rates in radio-collared moose, especially during the later spring months when ticks are heavily feeding. And when the fresh moose corpses are found, they’re covered in engorged winter ticks.
But winter ticks on moose were documented forever ago in places like southern Canada, so why are they suddenly an issue for moose in New England? Climate change. New England winters haven’t exactly been a walk in the park in the past decade or two, but winters have been getting shorter, and shorter winters are probably better for winter ticks. Here’s what people think is happening: first, substantial snow pack isn’t accumulating until much later in the season, which gives ticks more time to find and attach to a moose host before the vegetation and ticks are buried under the snow. And then that snow pack disappears earlier in the spring, which means that when engorged winter ticks bail off their moose hosts in the spring, the ticks have an easier time finding places to lay eggs.
There is a bunch of potentially interesting parasite ecology here – like, probably at least one PhD dissertation project to be had. If you’re interested, here are some books and articles about winter ticks and a moose that you should check out: