Martens are arboreal mustelids. They are agile climbers and skilled jumpers, chasing squirrels and birds among the treetops. Martens tend to den in hollow trees.
The fur of the martens is highly valued. A Siberian marten called the sable is especially prized.
The largest of the martens is an American animal called the fisher. It does not eat fish, but is the only effective predator of porcupines. It circles the porcupine, biting repeatedly at its face until the prickly rodent succumbs. Because porcupines kill trees by eating the bark around the circumferance of the trunk, fishers are valued as part of managed forestry programs.