Outdoors
The BDN outdoors section brings readers into the woods, waters and wild places of Maine. It features stories on hunting, fishing, wildlife, conservation and recreation, told by people who live these experiences. This section emphasizes hands-on knowledge, field reports, issues, trends and the traditions that define life outside in Maine. Read more Outdoors stories here.
Shed hunter Drew Maciel recently found two dead moose while searching for antlers this month. Both were covered in winter ticks and had significant hair loss.
He said he has encountered six dead moose with heavy tick loads this spring. About half were young animals, while the others were fairly large.
Moose biologist Lee Kantar recently discussed winter ticks and Maine’s moose on the Vortex Nation podcast.
Kantar said the state has been documenting winter ticks since 2006, though wardens noted them more than 100 years ago.
Unlike dog and deer ticks, which take blood meals from multiple hosts at different life stages, winter ticks spend their entire life cycle on a single animal. They attach to moose in September as larvae, then molt into adults, breed and the females drop off in spring to lay masses of roughly 1,000 eggs on the ground.
Those eggs hatch over the summer. The larvae climb onto vegetation and wait for a host to pass by.
“The biggest problem,” Kantar said, “is once it attaches to the moose in the fall, whether it’s 50 degrees or 50 below, it makes no difference. The tick is living on the moose.”
He said more than 90,000 ticks have been counted on a single animal and explained how heavy infestations can lead to death.
If roughly half of 50,000 ticks are females, they can each take more than 1 milliliter of blood to produce eggs. This drains so much blood from the animal that it becomes anemic.
Kantar said that unlike deer, which regularly groom using their teeth and hooves to remove ticks, moose do not.
“There are very systematic levels to how moose deal with winter ticks,” he said.
Sometimes the hair shaft breaks off from winter rubbing, leaving the white shaft — coining the term “ghost moose.” Some moose rub off all their hair, which can abrade the skin and lead to bacterial infection.
He believes rubbing the coat is a learned behavioral response. Many moose entering their first winter do not have missing hair. By their second year, they begin grooming and rubbing and continue to do so for the rest of their lives.
Kantar said that based on observations from radio-collared moose, animals captured in January can begin losing about a pound of body weight per day until little remains. By late winter, they may lose about 30% of their body weight.
“It’s a dead moose walking,” he said. “They basically go septic at some point.”
Small animals are the most vulnerable, he said. An 8-month-old moose calf captured in January may weigh about 400 pounds.
“It needs to be that much weight,” he said. “Even without ticks, a calf entering winter has no fat because it’s still growing its skeletal mass and is in a deficit.”
An 800-pound cow has the benefit of entering winter with fat reserves.
Even so, adult moose still lose condition. If a cow goes into winter pregnant, the fetus requires nutrition while tens of thousands of ticks are taking blood.
A moose’s winter diet lacks the protein needed to replace lost blood.
Kantar and colleagues in New Hampshire have found that cows often survive heavy tick loads but give birth to calves that are underweight, do not survive or struggle because the cow may not produce enough milk.
Using data from roughly 1,000 collared moose over 13 years, Kantar said adult mortality is relatively low compared to calves. Fall tick counts from index samples collected at harvest can help predict spring outcomes.
In some years, more than 70% of collared calves have died due to winter ticks.
The worst year saw 87% mortality. The best was 8%.
Kantar said there appears to be a strong link between moose density and tick abundance. More moose on the landscape means more ticks.
That link led to a five-year adaptive hunt in wildlife management district 4 aimed at reducing cow numbers and studying impacts on tick loads and reproduction. Results from that study are expected this summer.
While some have proposed treatments such as acaricides to manage winter ticks, Kantar said the scale makes them ineffective and expensive. Future management may instead focus on forest practices that help spread moose across the landscape.
Next steps include conducting fine-scale work with adult moose using high fixed-rate GPS collars. Kantar hopes to better understand where individual animals are each week over their lifetimes, and how forest management may play a role.
