Deer mice get nickname from their coloration
There's a mouse in the house! Indeed, the mere sight of a mouse, let alone the signs they leave behind, often invokes pure pandemonium among the human occupants of said dwelling. They gnaw on things, scamper about, they defecate, they infuriate. Though small creatures they are, woe is the homeowner who becomes overrun with those little mammals getting into things they shouldn't.
Deer mice are typically the culprits; those unwanted guests that sneak into your homes as the season of harvest wanes and Old Man Winter is but a few weeks from knocking at your door. They're looking, of course, for someplace warm -- someplace to call "home," but unfortunately, they usually don't come alone. Mice, as you all well know and loathe, reproduce quickly and can do so year around.
Last year was evidently a good year to be a mouse. Populations of some species in some parts of our region seemed especially high. Several people I know, particularly those rural folks, reported problems with mice in their homes. My home, regrettably, was not to be spared. I began noticing signs of the little rascals everywhere.
The first sign was underneath the sofa's cushions. The dog, I noticed one evening, was standing beside the sofa while curiously burying his large snout between the two cushions. He was obviously excited about something. So, I lifted the cushions and began searching deep into the sofa's inner-most hiding spots (those places we all know about where money and other odd-ball items collect) and was shocked to discover with my probing hands an amazing amount of dry dog food and acorns! A mouse, or more likely, mice, had been busy!
And so war was waged. A quick inventory of existing mousetraps revealed only three traps, and one of those was broken. But before the night closed in, two mice had taken notice of two traps baited with peanut butter. Subsequent nights and additional traps produced even more mice, too embarrassingly numerous to mention.
There are two species of deer mice in Minnesota: the white-footed mouse (Peromyscus leucopus) and the deer mouse (Peromyscus maniculatus), the latter of which is further divided into two subspecies. Both species of mice are very common, are nocturnal and are quite active throughout the winter. Of the two subspecies of deer mice, the prairie deer mouse prefers open habitat such as the prairie grasslands and farmland of western and southern Minnesota. Their diet consists primarily of weed and crop seeds and insects.
Meanwhile, the woodland deer mouse is more at home in forests and woodlands. This deer mouse differs from the prairie deer mouse in that it has a longer tail and is partly arboreal -- it climbs trees extremely well and often nests inside cavities. Their longer tail is probably an adaptation to tree climbing and helps the mouse balance on limbs as it searches for food such as seeds, berries, nuts, buds and insects.
The white-footed mouse is very similar in appearance and diet to the woodland deer mouse. Generally, their tails and ears are shorter than the woodland deer mouse. Additionally, their backs and sides are more reddish-brown in color. They range throughout Minnesota but are less common in the northeast.
The two species of Peromyscus are, by and large, collectively referred to as deer mice. But why? Why are they called "deer" mice? The reason is because of their coloration. Like white-tailed deer, the bellies of deer mice are white, while sporting darker coats above. The disruptive coloration (dark above and white below) does indeed resemble that of the white-tailed deer. Such a color pattern provides deer mice an advantage over predators by breaking up their outline, thus making them less visible as they travel about.
The life of a deer mouse begins in a nest made of soft material placed under a log, rock or other vegetative debris inside a cavity, burrow, hollow log, stump or even in an abandoned bird house. A female gives birth to a litter of three to seven helpless young. The young mice are cared for by their mother and are able to leave the nest in less than a month after birth.
A female is ready to breed and raise her own young at only 8-10 weeks of age and can rear four or more litters a year. You can tell a juvenile deer mouse from an adult by their mostly gray coat. They get their adult coat around 40-50 days of age. Deer mice, like other non-hibernating mice, are able to survive the winter by eating the food they store in underground caches (in a perfect world) or in some hiding spot inside our homes.
And about the latter: I haven't caught a mouse all winter, but I'm pretty sure they're around. I see their tracks in the snow outside, and every once in a while I think I hear them scampering across the rafters or climbing the studs within the walls. Unpleasant as it is to have a mouse in the house, rest assured they're reliably everywhere as we get out and enjoy the great outdoors.
Blane Klemek is the Bemidji area assistant wildlife manager, DNR Division of Fish & Wildlife. He can be reached at firstname.lastname@example.org