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Deer Mouse
Page Index:
- Distribution
- Characteristics
- Life on a Forest Floor
- Deer Mice and People
- Viewing Opportunities
- Identification
The Species: Peromyscus Maniculatus
Eyes bright, nose twitching, a deer mouse crouches hidden while voices and boots pass by. Then off it scampers through aspen leaves, along a log and into the safety of its tree stump nest. Unknown to many people, vermin or friend to others, this mouse may be North America's most widespread rodent and is one of the Yukon's liveliest small mammals.
Distribution
Deer mice occur through-out southern and central Yukon, but are absent beyond treeline in the north. They are very common in a wide variety of dry habitats, from gravelly beach ridges to spruce and aspen forests.
Characteristics
Young deer mice have dark gray coats with white feet and underparts, and a long tail that is distinctly dark above and white below. Most adults have buffy brown coats, but those in our southwest corner have grayish coats. Deer mice are so-named because their two-tone coats look like that of the white-tailed deer.
Yukon deer mice will fit easily into your cupped hand and weigh less than a first class letter. At about 20 grams, adults are fairly large in comparison to other Canadian deer mice.
Life on a Forest Floor
As buds burst open in the warmth of spring sunshine, deer mice leave solid earth below and climb into shrubs and trees to eat the rich new growth. They use their long tails to help grasp twigs or to keep their balance, and can climb a meter or higher. Back down on the forest floor, they also find spiders and insect eggs or larvae.
Deer mice start breeding in May, when males set up loose territories. These are areas from which other males are excluded, and to which females are attracted. Since male deer mice avoid each other and are quite sociable with females, there is no strong territorial defense. The breeding season lasts two or three months and females produce up to three litters during this time, each with an average of six young.
Newborn mice are blind and naked. Their large, night-vision eyes open within 2 weeks and they soon are covered in dark gray fur. At 6 weeks of age the litter is independent, but less than half of the young mice survive and few will live past their second winter.
Long summer days ripen fruits and seeds and hatch insects, all good foods for the increasing deer mouse population. Deer mice are active only during dark hours, so their summer food-gathering time is limited here in the land of the midnight sun. Since these mice must reach a certain weight before becoming sexually mature, this limited foraging time may be one reason why Yukon deer mice don't breed in their first summer. It may also explain why they have a relatively short breeding season when compared wi-th more southern deer mouse populations.
Numbers of deer mice peak when late August and early September frosts turn aspen leaves to gold. Young mice disperse from the site of their birth and may travel 10 times as far as their parents' home range. While looking for a good place to spend the winter, they often invade houses, cabins and sheds as well as their natural nesting sites of hollow logs, tree stumps or burrows abandoned by other animals.
Deer mice build ball-shaped nests of grass and line them with fur, downy seeds, or bits of cloth and paper. They stockpile seeds of grasses and forbs, first tucking them into their cheek pouches, then carrying them to a cache near their nest. The seeds are sorted carefully into different kinds and may total more than three litres.
Deer mice don't hibernate, but do escape the coldest times of winter by resting in a sluggish condition called torpor. When winds howl and temperatures plunge to -40 C, you can find them snug in their nests, often with company.
During the long winter nights, deer mice visit their seed stores and search for other sources of food. On top of the snow, they're exposed to the keen eyes of owls, and many an owl pellet contains deer mouse remains. Since Yukon deer mice don't breed during the winter, there are no new mice to replace those lost to winter hardships and predation by owls, weasels, and foxes. Populations hit rock bottom in early spring, but are soon on their way up once more with the onset of breeding in May.
Deer Mice and People
Because of its small size and nocturnal habits, many people don't even know the deer mouse exists. Of those who do, some see it only as a pest that invades their homes or garages and shreds mattress stuffing or leaves droppings on kitchen counters. Others enjoy the company of this perky rodent and some are glad to have it share a lonely cabin through the long winter.
Viewing Opportunities
If you've heard a scritch-scratch in your walls and found small, black droppings in your cupboards, you're likely sharing your home with a deer mouse. Put a dab of peanut butter in an open cupboard and watch patiently for your late-night guest. For a more natural viewing, try sitting quietly in the woods at dusk, remembering that deer mice prefer dry places and often run along logs or scamper around the bases of trees.
If you can't see the mouse itself, you may be able to find signs of its presence, like its droppings that look twisted and are pointed at one end. Perhaps you can also find its ball-like nest made of grasses and tucked into a stump, or one of newspaper shreds in an old boot. In winter, look in the snow for a delicate trail of 4 tiny paw prints in clusters spaced about a hand's length apart, along with the occasional tail drag mark.
Identification
To many of us, any wee creature scurrying among the leaves or peeking out at us from behind a cabin cupboard is a mouse. You can tell if it's the deer mouse by checking the following key features of deer mice and other Yukon small mammals:
- Deer mice have what we think of as the typical mouse shape. They have large ears and eyes, long whiskers, and a fairly long tail. Deer mice are brown or gray above and white below.
- Voles have short, chunky bodies. They also have very small ears, beady little eyes and short tails. Voles are brown above and gray below.
- Jumping mice look hunched up like kangaroos. Like kangaroos, they have large hind feet and extremely long tails. Jumping mice are yellowish-brown above and gray or creamy below.