Every fall, winter ticks in New England sit on shrubs or other plants waiting for a large animal to pass by so they can latch on and begin sucking out blood. This has a huge impact on the area’s moose, wildlife biologists say.
“They basically become zombies and die,” Eric Orff, a New Hampshire-based wildlife biologist, said. “We have zombie moose.”
According to estimates from New Hampshire Fish and Game, the Granite State’s moose population peaked in the late 1990s at around 7,000 to 8,000 moose. It has since declined to roughly 3,000 to 4,000.
Most tick species move from host to host frequently, but winter ticks find a moose, deer, or other animal around November and extract their blood for the entirety of winter. And it’s not just one or a couple ticks on each host. Rather, hundreds or thousands of ticks often latch onto a host. This is a process called questing and it has a huge effect on moose, particularly calves.
“April is the month of death for calves,” Orff, who works as a field biologist at the National Wildlife Federation and serves as vice president of the New Hampshire Wildlife Federation, said. “The adult ticks are feeding one more time before they fall off and they basically drain the moose’s supply of blood.”
Around April, the female ticks fall off their hosts to lay their eggs. If they land on snow as opposed to dry land, the eggs are less fruitful. However, as climate change represses winter weather, tick populations have boomed.
“Over the last 20 years, instead of one winter out of six or eight or 10 being truncated, now, a majority of them are,” Orff said. “So what has been found in more recent moose studies, including those done in New Hampshire and in Maine and Vermont the last two decades, is that it really significantly impacts the moose calves born that previous spring.”
While adult moose are better able to fend off the tick infestations, he said, 70% of calves don’t make it to 1 year old. And this also affects adult female moose.
Orff, who has been studying moose and other wildlife for decades, said that when he and his colleagues began this research in the 1980s, nearly all older female moose gave birth to two calves.
Now, he said, less than half the females even become pregnant. He said this is a result of being underweight from the ticks, but also because climate change is making summers warmer, which results in them eating less. Underweight moose are less likely to give birth.
“It’s really a double whammy,” he said.
A third factor, he said, is that south of the White Mountains brain worms have proliferated. While moose populations have plummeted, white-tail deer populations have nearly tripled from about 40,000 in the early 1980s to around 100,000 to 120,000 in the southern half of the state due to milder winters, he said. Brain worms are common in deer, and while those brain worms don’t harm the deer, they can be fatal to moose.
Orff noted the economic costs of lower moose populations. He said people used to travel to the North Country specifically to see the moose.
“Moose viewing in New Hampshire for a period of years was a $10-million-a-year industry,” he said. “I don’t know if there’s any companies that still do it. I think there are. But you used to be able to go out and, in a night, see a dozen or a half dozen moose at least. Now they may go several hours and see no moose.”
These die-offs also cause ecological issues. Henry Jones, moose project leader for Fish and Game, said moose carcasses serve as a food source for scavengers, which are seeing rising numbers in the wake of this population collapse. Jones said the past two years have been particularly severe for tick infestations.
To address this, the state is issuing more hunting permits. Jones said tick populations rise when the moose population has high density. By killing off moose, the survivors fare better, he said. The state is also working with the University of New Hampshire to study the conditions in which ticks proliferate best. Jones said this is all about “keeping them from getting really high density and causing this kind of cyclic relationship of lots of tick mortality.”
However, the hunting strategy still results in dead moose and low populations. Orff noted the conundrum.
“I guess that’s the debate,” Orff said. “Is it better to have far fewer moose and less sickly moose? … Baby moose who drop dead from no blood in April or taking some of them out that will be utilized by hunters eating them?”
Jones said the state is acting based on the wishes of citizens.
“We did a public survey to understand what the residents want with the moose population in 2024,” Jones said. “People want there to be the same or more moose, but they don’t want there to be more moose if they’re unhealthy.”
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