CONCORD, N.H. — Researchers studying New Hampshire’s declining moose population say some of the animals being tracked are thinner than they should be for this time of year.
The New Hampshire Fish and Game Department, in partnership with the University of New Hampshire, is in the first year of a three-year study into the causes of moose mortality and how changing weather patterns may be affecting the animals. It recently hired a helicopter wildlife crew to net 43 moose, place tracking collars on them and collect fur, blood and tick samples.
Researchers will use those samples and the tracking data to evaluate the animals’ immune systems and investigate whether winter ticks are the main factor in the declining population or whether there are other causes. That analysis is just starting, but biologist Kristine Rines said Monday that about 20 percent of the moose were thinner than they should be and were carrying winter tick loads that appeared heavy.
In an average year, a moose might carry about 30,000 ticks, but in a severe year, that number can be five times higher, Rines said. Unlike deer, moose are not big on grooming and have trouble shedding the ticks. Instead, they end up constantly scratching, which depletes their fur and leaves them susceptible to hypothermia, she said.
“They have a reduced immune response, so there are a lot of secondary infections that can drag them down,” Rines said. “As a result, in April, when you have a bad tick year, you have a lot of mortality. These animals literally just drop dead.”
If there’s snow on the ground when the ticks naturally drop off the moose in April, the ticks die without reproducing, she said. But shorter winters have boosted their numbers. The department also has collected ticks from moose killed during the fall hunting season and have been troubled by those findings, she said.
“Typically, you only see larval ticks on moose in the fall, but we’re starting to see adult winter ticks get on them, which is very unusual and suggests to us they may actually be able to cycle quicker than unfortunately we had hoped,” she said.
New Hampshire has about 4,400 moose, down from a peak of about 7,600 in 1996. Some of that decline was by design, Rines said, as the state sets goals for the population based on what the public desires. In some years, for example, the public wants fewer moose because moose-vehicle collisions have become a problem.
In Maine, where officials describe the moose population as “healthy and strong,” the state Department of Inland Fisheries and Wildlife is conducting a similar study. It recently placed radio collars on 60 moose in northern Somerset County.
New Hampshire plans to collar an additional 45 moose next January. Extremely cold weather made the recent outing difficult, Rines said, causing the helicopter to break down, shattering the equipment used to deploy the nets and rendering the tranquilizer dart guns inoperable. Following the deaths of four calves that were tranquilized, the crew did the rest of the collaring without the darts, she said.