Get Wild: The elusive pine marten
Editor’s note: This column has been updated to correct which animals are part of the Mustelidae family.
If your home adjoins the forest, or if you are hiking or cross-country skiing on forested trails, you might be lucky to spot a pine marten in the trees or scampering along the ground.
At first sight resembling a large, dark weasel, pine martens have been described as elusive, solitary and inquisitive. They are also vicious predators and great mousers.
The pine marten (Martes americana) or American marten, to distinguish it from the European pine marten (Martes martes), is also termed the “American sable” for the similarity of its beautiful dark brown fur to the Russian sable (Martes zellina).
Their luxurious, silky winter fur made marten pelts valuable, and hunting and trapping seriously depleted populations in the early 1800s. While pine marten populations have rebounded, destruction of forest habitat remains a threat, although martens are currently not considered endangered or a species of concern.
Pine martens are members of the large family Mustelidae, named for their musky scent glands used to mark territory. The family includes animals ranging from small weasels and ferrets to otters, badgers and wolverines. The marten’s genus, Martes, also includes the sable and the fisher, while another genus, Mustela, comprises the close relatives of weasels, ermine, ferrets and minks. Animals of both genera are characterized by silky fur and long, slender bodies. They are quick and agile, often scampering and pouncing on prey.
The pine marten’s coloration varies from gray on the head to brown on the body and very dark brown on the legs and bushy tail. It has lighter fur on its underparts and often an orange or buff throat patch. It’s ears are cat like, eyes large and claws sharp and curved. The undersides of their paws are furry to protect them in winter.
The pine marten’s small cousins in Colorado are the long-tailed weasel (Mustela frenata) and the ermine (Mustela erminea) or short-tailed weasel, both of which are brown in summer and turn white in winter, retaining their black-tipped tails. In contrast, the pine marten remains dark colored year-round. All three species do not hibernate, remaining active all winter.
Male pine martens are about 24 inches long with 8-inch tails and can weigh up to 2 pounds. Females are about 20% smaller. Martens are polygamous, breeding in June to August but with delayed implantation until February, after which young develop in 28 days. One to five young are born naked and blind in April in the grass-lined den. Young grow quickly and are weaned in about a month, reaching full size in about three months and sexual maturity in 15 to 20 months.
In captivity, pine martens can live up to 17 years and, in the wild, around 10 years. No predators have been reported for adults, but young may be taken by owls or wolves.
Pine martens prefer mature forests — especially with lodgepole pines, Douglas fir and spruce trees — and can be found at all elevations in these forests. Unlike other mustelids, pine martens are adept tree climbers and live mainly in trees, easily running between them. Males mark scent trails on tree branches.
Dens are in hollow trees, crevices or vacant ground burrows. Usually solitary, and often nocturnal, they mainly hunt on the ground at dusk and dawn when their prey is most active. Pine marten are opportunistic feeders, preferring squirrels, rodents, nesting birds, even carrion, but also eating fruits, nuts and insects. They kill prey with a quick, powerful bite to the back of the animal’s neck.
Pine martens are tolerant of people and can be accustomed to bird-feeding areas. At our rustic cabin bordering the national forest, we have been thrilled to occasionally see a pine marten at our winter bird feeder.
“Get Wild” publishes on Fridays in the Summit Daily News. Joan Betz is a retired biology professor from Regis University and a board member of Eagle Summit Wilderness Alliance, an all-volunteer nonprofit that helps the U.S. Forest Service protect and preserve the wilderness areas in Eagle and Summit counties. For more information, visit EagleSummitWilderness.org.
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