Dense horizontal woodland structure..........Old Growth Forest conditions.............Winter foraging runs rather than deep hibernation..........all variables that can work for and against Pine Martens in our Inter-Mountain West..............Now listed as a "Sensitive Species" by the U.S. Forest Service

The Western Pine Marten

Listed by the Forest Service as a Rocky Mountain region sensitive species

Glenwood Springs Post Independent

ENLARGE

Pine martens are a type of weasel that prefer to live in forests.

Unlike many people venturing into the wild of the High County, U.S. Forest Service wildlife biologist Ashley Nettles has encountered a pine marten. It had snuck up on her to eat her lunch.  "The young ones can be curious — like any young mammal, they don't know to avoid humans," she said. The creature, which is in the weasel family and is generally carnivorous, had its head in her Jello container. "The little guy ... came out with a red head," she said. "He was bouncing around in my lunch bag." After a few minutes of taking video and watching the long, slender animal with its bushy tail, she scared it off to encourage its fear of humans.

The pine marten is a generally elusive creature that's on the Forest Service's Rocky Mountain region's sensitive species list, Nettles said. That listing requires forest service personnel to consider how forest management practices will impact the animal's habitat. They need "complex, structured forests," she said, such as dense, multi-story forests comprised of several species such as spruce and fir. Nettles added that the stand structure may be more important than the species composition within the stand.  Understory complexity of logs, rock piles and outcroppings, stumps, fallen trees, slash, and boulder fields provides access to winter forage and rest, cover from predators and protection from the elements.
So, Nettles said, clear cutting and prescribed burns can have severe effects on martens. Even-aged lodgepole doesn't suit them very well," Nettles said, because there's fewer shelter and forage options — squirrels, chipmunks, voles and ground rodents aren't as prevalent on wide-open forest floors. They also opportunistically munch on plants, insects and birds, but "can shred a squirrel in no time," Nettles said, adding that they're generally not dangerous to humans, but they do have sharp teeth and shouldn't be pet or hand fed.
"Loss of old growth habitat is cause for concern and is a large reason they're on the [Rocky Mountain region] sensitive species list," Nettles said. She showed research that showed martens aren't likely to cross opening in the forest canopy that are larger than 100 to 300 meters wide. Pine martens live in all Rocky Mountain region forests except the Nebraska National Forest, Nettles said, and are rare enough that signs of one to 10 can be seen daily in the appropriate season or habitat. The home range is larger for males, when prey is more scarce and in fragmented landscapes. A Wyoming study showed that males averaged about 500 to 800 acres and females about 200 acres, which is thought to be similar to the marten's ranges in Colorado.
They make dens in log or tree hollows, squirrel nests and burrows. They are mostly nocturnal, and are generally solitary. Martens come together for breeding season, which is from July to September, and they give birth from mid-March to late April.
Nettles also showed research that shows populations can fluctuate dramatically because reproduction isn't always successful, because of the way martens move and their mortality. In winter, they don't stop being active unless severe weather moves in. They tend not to migrate according to altitude, either. Instead, they keep foraging on the ground or in trees — Copper Mountain resident Kim Fenske said he's seen one or two roaming about during his winter excursions into the backcountry.