BANGOR, Maine — For the past several years, biologists, hunters and moose-watchers have spent a lot of time talking about “winter ticks.”
Also known as “moose ticks,” these insects hitch a ride onto a host — in these parts, that’s often a moose — and spend nearly their entire lives there, supping on moose blood. The effects of that parasitic existence can be devastating, especially for young moose.
The Maine Department of Inland Fisheries and Wildlife, along with partners at the University of New Hampshire, have been working on a long-term research project over the last three years that biologists say will help them understand the answers to some key questions.
“The key ingredient in this winter tick [research] is [discovering] the frequency of events [that cause spikes in moose mortality], and if it’s just happening in western Maine, or everywhere,” said Lee Kantar, the DIF&W’s moose biologist.
The study involves fitting cow and calf moose with GPS collars in three study areas — one in northern New Hampshire, another in western Maine and a third in northern Maine — at different latitudes to see if moose and ticks interact differently in differing climates.
Kantar explained that for a moose, the ideal situation would involve adult ticks dismounting their host in the early spring and ending up in a snowbank. That may be more likely to happen in northern Maine than 200 miles south in New Hampshire.
“We think that once [the female tick] is fully engorged [with moose blood], pretty shortly after that she’s going to fall right off,” Kantar said. “And then she’s either going to fall into snow and hopefully die a miserable death, or she falls off and slinks away and survives until she can produce eggs and lay those eggs.”
Kantar describes the research as a true “work in progress,” and said biologists are gathering important data each year. One point of interest from the most recent winter: Calf mortality in Maine’s western study area nearly mirrored the results from the first year of the study, when 70 percent of calves perished during the winter. In the first year of studying moose farther north, 20 percent fewer moose died, according to Kantar.
Biologists know ticks are taking a toll. They’re working to find out if northern moose face fewer challenges from the ticks than southern moose, and to find out how frequently moose face severe challenges from ticks.
Understanding how winter ticks operate, and what sets them apart from other species of ticks, is essential to understanding what moose are up against, Kantar said.
One host for life
Maine has all kinds of tick species crawling around in its forests, terrorizing the townsfolk and spreading disease. And ticks all have three life stages: They hatch as larvae, later become nymphs and finally reach adulthood. During each phase, they seek a blood meal from a host.
But the winter tick is unique in an important way, according to Kantar.
“The big deal about winter tick is that it spends all those life stages on the same host. This one tick gets a blood meal on that same animal — in this case a moose — as a larvae, as a nymph and as an adult,” Kantar said. “So you have one tick getting all of its blood from the same animal, which is different from other ticks, which are taking blood from many animals.”
Winter ticks aren’t new to Maine, and exist across the nation, Kantar said. And there’s really no way to know whether there are more winter ticks on the landscape now than there were 10 or 15 years ago. Hunters and outdoors enthusiasts have been reporting dead moose with high tick loads on them for years, and that’s part of the reason biologists are studying their effect so closely now.
The winter ticks begin their life cycle lying on the ground as eggs through the summer. Then they hatch into larvae in the fall, climb a shrub and wait for an unsuspecting host.
“Another thing that’s different about winter tick in this stage, the female lays thousands of eggs, en masse, so when they hatch out, they hatch out en masse,” Kantar said.
And when they hop onto a passing moose, they also do that as a large group.
“The animal comes by, [the ticks] sense that animal going by, and they all attach together, like a barrel of monkeys,” Kantar said.
Some potential hosts, like deer, sense those larvae and try to rid themselves of them. Others, like moose, don’t, Kantar said.
So the ticks go for a ride that can last for months.
“They’re on the moose, thousands of [larvae], and they’ll travel their way to different parts of the moose and take a blood meal,” Kantar said. “Then they essentially hang out there, on the back of the moose, and molt. They’ll shed their exoskeleton and become a nymph.”
Then the process continues, until that nymph eventually turns into an adult, and the adult chooses to feed just before the females drop off to lay their eggs. By May, the adults are dead, but the next generation is on the ground, awaiting their own journey on the back of a moose.
How many ticks?
Anyone who’s plucked a tick from their pet, child or themselves can understand the dread that accompanies the discovery of the creepy-crawly critter. Humans’ concerns typically center on the possible transmission of tick-borne illnesses like Lyme disease.
For moose — especially young moose — there’s a different hazard: They can essentially be sucked dry by thousands of winter ticks who each eat three blood meals off their host.
How many thousand ticks does it take to put a moose in severe danger?
Kantar said biologists are still studying that, but researchers in New Hampshire have established a baseline estimate that may surprise you.
“They’re doing a whole hide count [of ticks on deceased moose]. What we found, when talking with them this week, is that we’re talking about about 50,000 ticks being a threshold,” Kantar said. “And they have counted up to 90,000 ticks on a single animal, feeding.
Kantar said with tick loads like that, younger animals are in particular danger.
“If you have a high number of ticks on a small moose, it could result in the death of that animal,” Kantar said. “People have been trying to wrap their brains around it. It’s hard for me to wrap my brain around the fact that an animal of that size could die from winter tick. But when you say there’s 50,000 ticks removing blood within a very short time period, usually in the later winter and early spring, that moose is losing so much blood that it can’t replace that.”
