Ticks are killing dozens of moose calves in Maine

Ticks could become more of a problem for the large, antlered creatures as the climate warms

Ethan Freedman
Climate Reporter, New York
Tuesday 24 May 2022 22:34
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Ticks have killed 60 of the 70 moose calves tracked by state biologists in part of Maine, quite literally draining the life from the months-old animals.

While moose calves can weigh hundreds of pounds, that’s often no match for tens of thousands of the blood-sucking critters who attach themselves in late fall and feast on the antlered behemoths over the long New England winter.

The ticks aren’t new, Lee Kantar, the state’s lead moose biologist, told The Independent. But a combination of a lot of moose and a lot of ticks has been devastating to this year’s calves in one northern part of the state.

And as the climate gets warmer and the winters get shorter, these ticks might just become even more of a pest to the north’s iconic and massive hoofed creatures.

“Every day where it’s so ‘mild’, there’s more and more ticks getting on a moose,” Mr Kantar says.

Maine Public Radio first reported the news of this year’s moose deaths.

Mr Kantar and his colleagues have been tracking moose calves in this part of Maine for a while, and for the past three years in this 2000-square mile chunk of land in the state’s sparsely populated north.

In the first year, around 38 per cent of the calves died, he says. In the second, 59 per cent didn’t make it through the winter.

But this year, a whopping 86 per cent of the moose calves in this area didn’t live until springtime. These results aren’t necessarily representative of moose in other parts of the state or other states, Mr Kantar says — but it does mean a lot of calf deaths in a pretty wide area of the state’s moose habitat.

The culprits aren’t the same kinds of ticks you usually find on animals and people after a walk in the woods, but an unusually crafty species called the winter tick.

Many tick species bounce from creature to creature over the course of their life, Mr Kantar says, upgrading to fresh meat as they grow. But winter ticks spend their entire lifespan on one animal.

In the fall, they climb onto branches and shrubs as larvae in groups of hundreds and attach themselves to animals walking by. Most animals can recognize that they’ve been covered in tick larvae, Mr Kantar says — imagine trying to ignore a clump of hundreds of tiny ticks attaching themselves to your skin.

But moose just don’t realize the winter ticks are on them until the pests get much larger, Mr Kantar says. At that point, the animals will try and use its hind legs or a nearby tree to scratch them off, sometimes scratching so hard that they end up with bald patches, he adds.

There could be tens of thousands of ticks on one animal, however — and for the calves, all that effort might be too little, too late.

For one, the calves often aren’t very good at scratching, Mr Kantar notes. But they’re also smaller than the adults, and less prepared for the winter.

On average, an adult female moose weighs a little more than 800 pounds and an adult male weighs a little more than 1,100 pounds. And in the summer and fall, the animals fatten up, Mr Kantar says, accumulating reserves of energy to get through a New England winter mostly devoid of good protein.

The same isn’t true for the calves. An average moose calf weighs around 400 pounds, Mr Kantar notes, and instead of fattening up in the summer and fall, they’ve used most of their energy to get bigger since being born in late spring.

That’s not usually too big of a problem — unless that moose calf is covered in ticks.

An adult female tick can suck out around one millilitre of blood, Mr Kantar says, meaning if you’ve got 30,000 ticks on you, you’d lose 30,000 millilitres — or 30 litres (almost 8 gallons) — of blood over several weeks. For reference, the average human has a little less than 1.5 gallons of blood in total.

With all that blood loss, coupled with a lack of fat reserves and very little quality food around during the cold season to replenish your energy, a calf may not make it to the more hospitable springtime.

“The moose is wasting away because it’s trying to build up its blood supply, but it’s losing the battle and it’s causing a tremendous and rapid weight loss,” Mr Kantar says.

Part of the reason the ticks have spread so widely in that area is that there’s a lot of moose, which Mr Kantar attributes to commercial forestry creating ideal habitats for the animals decades ago and a relative lack of predators.

When you have a lot of one animal in a close environment, parasites and pathogens can spread pretty easily. Think of COVID, Mr Kantar suggests — more people packed into smaller areas can spread disease more efficiently. And in areas with fewer moose, like New York’s Adirondacks, there’s less of a winter tick problem, he notes.

But as the climate warms, the moose could gather more tick larvae in the fall — when the ticks are actively out looking for hosts — before the winter really sets in, Mr Kantar says.

Warmer weather could also boost another iconic North American antlered animal: the white-tailed deer. And that could be bad news for the moose.

“White-tailed deer and moose, when deer are at higher densities, do not mix well,” he says — noting that deer thrive in more mild winters and can carry parasites like ticks that don’t affect them as much as they affect moose.

It’s not entirely clear what the long-term impact of warmer climates might mean for moose populations in northern New England. But there’s plenty of reasons why people would want to keep moose around into the future — from their role in the local ecosystem to the tradition of moose hunting to the animal’s place on the Maine state flag, Mr Kantar notes.

“Moose in and of themselves are clearly iconic in the northeast,” he says.

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