A mysterious mammal’s comeback 

Although weasel species tend to look alike, with low-slung bodies, sleek heads, and long tails, the marten stands out. They’re thoroughly mid-sized – considerably larger than mink and ermine; considerably smaller than fisher and otter. They have fox-like ears, which make their profile distinct from the other weasels’ more streamlined appearance. And their colors are one-of-a-kind.

“In the summer, the martens have this unbelievably bright orange throat patch – like hunter orange,” says Jillian Kilburn, a wildlife biologist with the New Hampshire Department of Fish and Game. That patch makes the marten the most brightly-colored mammal in our region, she explains. The rest of its body is a deep chocolate brown in summer and a lighter tawny color in winter.

Marten are a threatened species in New Hampshire and endangered in Vermont. They’re known for favoring spruce-fir forests in the far north. And they love snow – thriving under a deep snowpack where they hunt mice, voles and red squirrels.

Martens also love trees. They love to climb them, and they love the little spaces in the snow made by roots and fallen branches. Martens thrive in old growth, Kilburn says, where there are lots of fallen trees and gnarly root systems, though it is possible to manage the landscape [for “manage,” think logging] and keep martens pretty happy. To co-exist with martens, a logger would look to retain
60 percent canopy cover after a harvest, leave a few big, dead trees, and leave lots of tops and branches on the ground.

Something in the northern third of New Hampshire is making martens very happy. While attempts were made to restore the marten population in the 1950s and 1970s, Kilburn says the population has really taken off in the past 10 years.

She even gets calls about martens breaking into northern camps and stealing food.

Martens are not as happy in Southern Vermont. Twenty years ago, when the Vermont Fish and Wildlife Department tried to restore martens to the south-central Green Mountains, camera traps recorded only two of the 115 released animals in the area five years later.

Part of the problem may have been a lack of deep snow. The other problem, though, was competition: The cameras did record an awful lot of fishers

A fisher is another member of the weasel family that can weigh up to 10 times more than a marten. “Fisher and marten are prime competitors,” says Chris Bernier, fur-bearer biologist for the Vermont Department of Fish and Wildlife. “Martens do better in deep snow. Without deep snow, the fisher has the advantage.”

Bernier says that Vermont’s trapping records indicate that the fisher population surged during the time the marten were released. He suspects it was just unlucky timing for the marten reintroduction project.

Last year, trappers reported two martens in southeastern Vermont, offering hope that either martens are returning to the area on their own, or that the survivors from the restoration effort hung on long enough to reproduce.

Alexej Siren, a graduate researcher at the University of New Hampshire, also wonders about the effect of fisher on New Hampshire’s martens. When his research projects began in late 2010, Siren says, the state didn’t have much information specific to New Hampshire martens. “What are their home ranges compared to martens in Maine or out West?” he wondered.

Siren has radio-collared 13 martens and tracks them with a hand-held receiver on weekly trips to the study site, and with a receiver mounted in a newly built wind farm. Because Siren began collecting data on the marten before the wind project was built, he will be able to see what influence the wind farm has on the martens’ home ranges.

He also samples the tracks of other predators in the area. Because martens thrive in deep snow, Siren is curious about what effects the maintained road to the wind farm and the packed snow on winter hiking and snowmobile trails might have in bringing competing predators to the site.

“Out West, backcountry roads and trails are introducing coyotes to lynx habitat,” Siren says. With the martens in New Hampshire, “I’m most worried about fisher.”

Siren is just halfway through his fieldwork, but he’s already learned that martens migrate from low-elevation hardwood forests to higher elevation spruce-fir forests after the leaves fall. In Vermont, Bernier plans to survey for martens with camera traps and hopes that DNA tests will show where those trapped martens came from, or if they are descendants of the restoration project.

Now that marten numbers are increasing, perhaps we’ll be able to learn a lot more about this secretive animal.

Madeline Bodin is a writer living in Andover. The illustration for this column was drawn by Adelaide Tyrol. The Outside Story is assigned and edited by Northern Woodlands magazine and sponsored by the Wellborn Ecology Fund of New Hampshire Charitable Foundation: wellborn@nhcf.org