They have a high metabolism, thus require a lot of food for energy. This intense need for food makes them easy to trap. Mice and other small rodents are martens' primary prey, but they also eat squirrels, hares, shrews, birds, bird eggs, amphibians, reptiles, insects, fish, crayfish, nuts, fruits and carrion. In the winter, martens will tunnel under the snow in search of mice and other small mammals. Breeding Biology Pine martens first mate when they're about two years old.
Courtship consists of playing and wrestling, followed by mating.
Both males and females may mate with several partners during the breeding season. Although the female marten's eggs are fertilized by mid-summer, they don't fasten to the wall of her uterus until January or February. The female makes a den in a hollow tree, stump or rock crevice, lines it with leaves, moss and other vegetation and gives birth to 2- 4 kits. The male takes no part in rearing the young. The sparsely furred, newborn pine martens have their eyes closed.