Sparse herd has fewer chances to encounter deadly ticks
By Francesca Krempa
Most large mammal ecologists might shudder at an entire animal population of just 700.
When it comes to saving Adirondack moose from winter ticks, though, such a small and fragmented herd might actually be a good thing.
For years, winter ticks have threatened moose populations across the Northeast, particularly in “hot spots” like northern New Hampshire and western Maine. Some scientists are worried that climate change is drawing winter tick populations into the Adirondack Park, endangering the already elusive native moose populations. The size of the 6 million-acre park’s current population can be disconcerting. While Maine has 60,000-70,000 moose, researchers estimate that there are only 600-800 in the Adirondacks, putting the species at-risk if disease ever swept the herd.
But in the case of winter ticks, this low population density might just work in the moose’s favor. In places like Maine, where there are simply more animals per square mile, there’s a higher chance they’ll stumble on and spread the blood-sucking parasites.
“Thank your lucky stars, you’re just not going to have a tick problem,” said Peter J. Pekins, a long-time moose biologist and professor of natural resources and the environment at the University of New Hampshire. “It’s just a typical host-parasite density relationship. And as long as the host density is low to moderate, you’re just not going to have that problem that we see over here (in New Hampshire).”
The potential threat of winter ticks in the Adirondacks has plagued local researchers for a long time. Tales of moose literally being eaten alive by the parasites have circulated through academia and the mainstream alike. In 2018, The New York Times highlighted Pekins’ moose-tracking research in New Hampshire and Maine, where he recorded an average of 47,300 winter ticks on 179 different moose calves.
While these one-host ticks have always preyed upon moose and other large mammals in the Northeast, climate change seems to have propelled their threat. Pekins, who has researched moose and deer in New England for more than 25 years, explained that winters are getting shorter, lengthening falls when these parasites thrive. Temperatures used to drop in early October, killing baby ticks “questing” for a moose to come along.
Now, autumns are prolonged, giving the baby parasites more time to hunt their hosts. As moose wander through tall grasses and shrubs, questing ticks latch on in clusters of hundreds and thousands. Here, they’ll spend their winters feeding off their hosts, eating their fill before spring when they’ll finally unlatch. But if there’s no snow on the ground in spring—a symptom of climate change—pregnant female ticks will lay eggs, and the whole cycle starts again.
“Their activity is driven by ambient temperature,” Pekins said. “The time period that these larvae can get on a moose normally—if you just delay winter two weeks, you can increase that time period by 20-25 percent. The math is very easy about how you can get over a threshold of ticks very quickly.”
These shortened winters have some Adirondack scientists worried about the future of the park’s herd, especially as populations in neighboring states wage war on winter ticks.
Krysten Schuler, a wildlife disease ecologist at Cornell University’s Animal Health Diagnostic Center, is a lead researcher in New York State’s official moose management study. Funded by the Department of Environmental Conservation and the Federal Aid in Wildlife Restoration Act, Schuler and other biologists are actively monitoring the health and trajectory of New York’s herds.
As a wildlife disease ecologist, Schuler’s role is to assess the health and pathology of the moose in the park. Using live-captured animals and dead carcasses from vehicle collisions, she’s able to collect comprehensive health data on different physiological criteria, including parasitic infections like brain worm, liver fluke and winter ticks.
“We don’t actually see winter ticks causing a problem in New York moose yet. We’ve definitely documented them, but when we do, it’s in low numbers,” Schuler explained. “But we’re worried we might be sort of at the bleeding edge of an epizootic, (that), you know, the outbreak is just getting started now.”
While Schuler assures that the moose living in Adirondack Park are generally healthy, the size and concentrations of moose are worrisome from a pathological standpoint. Simply put, it wouldn’t take much to wipe out a small herd.
Jacqui Frair, a large animal ecologist and director of the Roosevelt Wild Life Station at the State University of New York’s College of Environmental Science and Forestry, has been researching moose in the park for the past seven years with the New York moose study. She and her team monitor the moose population via aerial helicopter surveys, tracking where exactly the moose live and how their habitats support them. Frair’s findings show the small amount of moose the park does have are fragmented into very specific regions, normally near timber easements where low-hanging twigs and leaves are easily accessible.
“Not only do we have only 700 moose, they’re really only concentrated in like, three spots,” Frair explained. “Moose exist everywhere in the park, but in incredibly low density. It’s not even worth us to try and survey and count them in 75% of the park.”
Frair echoes Schuler’s concerns—a potential assault, like disease, could threaten the survival of the entire herd. But in the case of winter ticks, such low density might actually put the moose at an advantage.
“We don’t have many moose, and that’s probably a very good situation to be in,” said DEC biologist Jim Sickles, who manages the New York moose study for the agency. He said one of the best ways to ensure a healthy moose population is to keep moose densities low. It gives parasites fewer opportunities to acquire hosts and reproduce. In places like Maine and New Hampshire, there are substantially more moose to pick up ticks and perpetuate reproduction.
Still, that doesn’t mean Sickles and the rest of the moose study team aren’t taking all the necessary precautions against winter ticks.
“We’re in a unique situation where at a very large scale, we have very few moose,” he said. “But at some micro-scales, we have densities that may need to be managed in some way.”
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Sickles isn’t sure what those management tactics look like quite yet. Using findings from the ongoing New York moose study as well as public perception surveys, he intends to develop a formal moose management plan to determine the best way to maintain healthy populations.
In the meantime, the state has tasked Schuler with tracking the status of winter ticks, specifically. Schuler and her team have already received reports of anemic looking moose—those with “telltale characteristics” of winter ticks, like unkempt appearances, missing patches of fur, and low body weights—in a few areas around the park. Using cameras, the team plans to continue tracking moose that display these physical characteristics to keep tabs on the persistence of the parasites.
“We need to do the study to catch it,” Schuler said. She explained studies normally happen after a problem has already occurred. Starting research now, before the winter ticks have decimated the population, might allow them to avert an epizootic. “We don’t get this opportunity very often,” she said.