Researchers examine impacts of parasites, lack of prime habitat
By Mike Lynch
We walked along the dirt road through the woods, our heads and eyes down, looking for moose tracks.
The previous morning a driver had spotted a 1-year-old moose in the road walking in circles and making no effort to evade the vehicle.
One of the Shingle Shanty Preserve and Research Station landowners relayed that information to Steve Langdon, director of the 23-square-mile private preserve west of Long Lake.
The next morning Langdon invited me to join him at the preserve to find the animal. It appeared as if it were infected by a brain worm, a parasitic worm that often grows up to 8 inches long and is as wide as a human hair or two. In moose, the worms migrate through their brains and spinal cords, causing neurological damage and eventually death. Moose ingest them accidently by eating infected snails or slugs that are living on vegetation they are feeding on.
As we continued, I expected to find the animal dead or lying prone. We suspected the moose hadn’t moved much in the past day. We found a few tracks but were uncertain where they entered the woods. We hiked through a field following wildlife trails through trampled vegetation and checked for signs of prints at a sand pit.
We split up and Langdon called out.
“There’s some tracks down here by the stream bed,” he yelled. “It’s all churned up.”
But after tromping through the mud, the moose had left the stream, and the tracks disappeared. As Langdon searched another nearby lead, I followed the waterway downstream. I crossed, and started walking on an old logging road, less than a minute or so behind the animal that had stomped in the mud.
Then I spotted it. The moose stood quietly on an overgrown woods road, eating leaves from the nearby trees. Appearing emaciated, it moved slowly and seemed unaware of my presence.
I watched it for several minutes, excited by the idea of seeing a moose in the wild but saddened by the knowledge it was in its final hours of life. After a few minutes, I left the woods to alert Langdon, who was now back at the truck honking the horn trying to find me. I led him to the scene where the young moose noticed us, its head slightly tilted. It stood still. It didn’t charge off. It looked vulnerable.
The next day, Langdon returned with state Department of Environmental Conservation wildlife personnel and found the moose in the same vicinity.
That day, Kevin Hynes, DEC’s wildlife health program leader, walked within 35 feet of the roughly 225-pound male with antler nubs.
“We couldn’t really seem to get him moving in a straight line,” Hynes said.
After the moose was killed with a shotgun, the DEC unit performed a field necropsy, bringing back the head and spinal column to the state wildlife health lab for closer analysis.
They found two brain worms.
Moose returned to New York in the 1980s after disappearing in the 19th century due to unregulated hunting and logging that decimated northern forests. Now there are an estimated 550 to 900 in the Adirondack region.
But that number hasn’t grown as scientists expected and is significantly smaller than other northeastern states, whose populations flourished in the 1990s. Vermont and New Hampshire each estimate its population at about 3,000, while Maine has somewhere between 60,000 and 70,000.
Why is the Adirondack population smaller? There are several theories and potential factors. Some scientists point to a lack of quality food in the Adirondack Park due to limited logging operations and large swaths of protected lands. Moose like to feed in young forests that sprout in areas that have been logged or are impacted by natural disturbances such as fires or windstorms.
There are some good moose habitats, including Shingle Shanty Preserve. Langdon said he’s seen many moose on the property in the last 13 years because of their moose habitat components. A major windstorm in 1995 knocked downed large swaths of trees, creating young forests alongside bog habitat where moose feed and cool off during hot summer months. About a decade ago, DEC counted 24 moose at the northern end of the preserve’s property.
Langdon is concerned, though, that fewer moose are using the land now as the trees get older.
Good moose habitat exists in other areas, including the northern part of the park, where there are ongoing logging operations, bogs and little development.
Other theories about why the Adirondack’s populations is small focus on brain worm and giant liver fluke, and that’s a central part of a current moose study by the DEC, Cornell University, SUNY College of Environmental Science and Forestry and Native Range Capture Services.
Liver fluke is parasitic flat worm that can grow up to 8 centimeters long and 5 millimeters thick. Moose get infected by eating infected snails or liver fluke larvae that are attached to aquatic vegetation. Once inside the moose, it migrates through the digestive tract to the liver, where it causes damage.
Scientists don’t have a lot of information about how moose die in the wild because those incidents often occur deep in the woods. To find out more about deaths, particularly with young moose, researchers went to the northern Adirondacks. In January, they attached GPS collars on 14 of them—12 calves roughly 6 months old and two about 16 to 20 months old. They plan to fit another 18 young moose with collars this winter.
The collars are tracking devices that emit a signal when the moose dies. This is key because researchers want to get to the moose promptly to do a field necropsy and collect body parts that can be analyzed for a cause of death.
Krysten Schuler, a wildlife disease ecologist with the College of Veterinary Medicine at Cornell University, said a prior study looked at female adult moose and found their survival rates were good and they were getting pregnant and having calves.
That information, along with data that juvenile moose were dying in large numbers in neighboring states due to the winter tick, was a main factor that led to this recent study.
“We hypothesized that juvenile moose were not making it to adulthood to reproduce, have the population grow,” Schuler said.
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Deer as hosts
In the Adirondacks, there aren’t grizzly bear and wolf populations that feed on moose. Instead, they are killed by motor vehicles, complications from injuries such as broken ankles, natural causes and parasites.
One of the concerns about parasites—liver fluke, brain worm, and winter ticks—is that all three use deer as hosts. The organisms don’t seem to have as big of an impact on them as they do moose. Instead, deer seem to spread the organisms throughout the environment. Liver fluke and brain worm are passed on through deer feces, while winter ticks are shed from their fur.
Climate change isn’t part of the current study, but it plays a large role in the moose population because warming temperatures have allowed deer to expand their range and share more habitat with moose, whereas in the past they lived in more separate areas.
Jen Grauer, a Cornell graduate student who is studying the moose population, said winter ticks appear in the Adirondacks in low abundance, but brain worm and giant liver fluke appear more common than in neighboring states. They are essentially filling the roles of predators, she said.
So, one of the focuses of the study is to better understand the liver fluke population carried by snails and deer. This summer, Grauer and several technicians spent time collecting water from ponds and lakes throughout the northern Adirondacks. Using environmental DNA techniques, they can test for the presence of the parasite.
Winter ticks and climate change
In other parts of the Northeast, winter ticks play a large role in thinning those populations. Moose can carry tens of thousands of ticks, causing the animal to lose significant amounts of blood and hair. The weakened animals become more vulnerable to disease and malnutrition.
In recent years scientists have said that winter tick populations haven’t thrived in the park because there aren’t enough moose to serve as hosts, but the threat is looming because of their prevalence in the Northeast and milder winters mean their populations can take hold.
Ticks leave the bodies of dead animals. So to determine the impact of winter ticks in the Adirondacks, researchers have set up trail cameras, hoping to capture images of moose in the winter. Researchers will be looking for things such as hair loss on the animal.
The cameras are set up in areas with varying moose and deer densities to try to determine if the parasite spreads more in different situations.
“Deer are programmed to constantly groom,” said DEC wildlife biologist Jim Stickles walking through a high deer, low moose habitat in Black Brook. “Moose didn’t evolve in areas with a lot of ticks.”