From "The Wild Bunch"
The Marten
The marten is a small, housecat-sized predator with brown fur, an orange chest, black legs, and a greyish face. Weighing between one and five pounds, martens have the elongate shape, slender torso, short legs, and fox-like snout of the weasel, to which they are related. In fact, the marten, fisher, and wolverine are all members of the weasel family.
Martens posses many characteristics shared by one or more of the forest carnivores, which makes them a good introduction to the entire group. First, not only do martens need boreal forest, they need relatively undisturbed, mature boreal forest. The marten is one of the most old-growth dependent mammals on the continent.
Second, overtrapping for its beautiful fur was a major cause of the marten’s decline, as well as that of all the forest carnivores. In the last century, curiosity and a baited trap have killed hundreds of thousands of martens.
Third, it is only fairly recently that we are learning some of the most basic facts about the biology and habitat requirements of the marten and the other forest carnivores. For example, for many years, biologists assumed that martens spent most of their lives high in trees, using branches as their highways, and living on a diet of tree squirrels.
It’s partly true, martens are very much at home in the high branches, and they sometimes do chase down a squirrel in a tree. The other truth, however, is that martens spend most of their time on the ground, exploring territories as big as four square miles. In the winter, they spend much of their time beneath the snow’s surface, resting, staying warm, and hunting for voles.
Martens eat so many voles year-round that these small mice-like mammals may make up the largest part of their diet.
The marten’s prey also includes mammals that range in size from chipmunks and pikas, to snowshoe hares and yellow-bellied marmots. Martens also kill adult birds as small as nuthatches and as large as ruffed grouse. One wildlife photographer searches for martens in part by investigating every bird squawk that he hears. Martens also forage for berries, insects, and birds’ eggs when they’re in season.
Finally, marten are very willing to eat carrion – the carcasses of animals that they do not kill – a fact that makes them easy to trap.
Like many other predators, a marten feeds itself by being endlessly alert, inquisitive, and exploratory; fully engaged by the world in which it lives. Like other small animals, martens are lightning quick, and often seem to be in constant motion.
The marten zig-zags everywhere, out of a treewell to a nearby snag, which it climbs to investigate a cavity ten feet up. It runs across the snow and under a downed log. It pops out on the other end and runs again, making a sudden right angle turn to investigate a hole in the snow, where it stops to sniff and listen – is there a vole down there, before continuing on its way.
Martens are as active as they are in part because both their small size and narrow body shape mean that they lose heat to their environment relatively quickly. They have to keep hunting and eating – an average of two to three voles per day – just to stay warm.
The marten is narrow because it hunts in an environment of tight squeezes where the skinnier it is, the more places it can go. Being thin allows the marten to fit into tight cracks and tree cavities, and weave through the tangled maze of brush and downed logs on the forest floor,
During the winter, the marten’s streamlined form allows it to explore and hunt the narrow passageways and dens used by the voles under the snow. However, being long and thin has its disadvantages, this shape increases the body surface where heat is lost.
The combination of shape, low body fat, and lack of a warm coat means that martens need habitats where they can find a place to stay warm and find food often.
Trappers were the first to notice that martens preferred "the gloom of the firs" and seemed to disappear when forests were cut down.
The explanation lies in the nature of the mature, old growth forest itself. Old forests contain trees in all stages of life and death. Most importantly, old forests include a lot of dead wood, from standing snags to downed logs and branches on the forest floor. Martens prefer these older forests that have lots of woody debris on the forest floor, but biologists are finding out that martens can adapt to other kinds of forests – even severely burned ones – as long as an abundance of downed wood remains on the ground, and large numbers of voles and small mammals live in the area.
In winter, downed logs and woody debris provide crucial openings in the snow surface to the runways below the snow where martens hunt their prey and seek shelter in and under rotting logs. Most younger forests simply haven’t had the time to accumulate many downed trees on their floors. In a young forest lacking these downed trees and limbs on the forest floor, martens are locked above the snow’s surface, unable to reach their prey, hide from other predators, or find shelter from the cold.
The marten's two of its closest friends are the vole, who in its death provides food for the marten, and the tree, which, in its death, will provide the marten with access to more voles, a way to escape from other predators, and a haven from the cold. But more than any other factor, the critical ingredient to the martens success is for us humans to save the right kind of places so that the marten can find everything it needs in order to survive.
marten | forest | slideshows
