TIM LOCKLEY: Deer mice might try to come in from the cold

There are 15 species of white-footed mice in the U.S. One of them, the deer mouse, is probably the most common mammal found in North America, from southern Canada all the way into southern Mexico and from the eastern Rocky Mountains to the East Coast.

Although they don't normally invade occupied homes, occasionally, with the onset of cold weather, white-footed mice will take it upon themselves to come visiting. Fortunately, these are "country mice" for the most part and are rarely found in urban settings and seldom located in suburban areas unless there are considerable open areas like parks or fields nearby. But, as we continue to invade their home territory and construct more and more homes and businesses in rural areas, the opportunities will continue to open up for their intrusion into our homes and buildings.

All of the white-footed mice, as their name would indicate, have white feet. They also have white undersides and brownish upper surfaces. Their tails are covered by short, fine hairs and can be as long as their bodies and head. In comparison to the common house mouse, deer mice have much larger eyes and ears. Most people think of white-footed mice as being "cuter" than house mice. They also lack the "mousy odor" that we associate with house mice.

White-footed mice are seldom seen by humans. They tend to be active from dusk until just after dawn and prefer to avoid contact with people. Outside, they nest in underground cavities beneath roots of trees or shrubs, beneath a board or log or in a burrow made by another mammal. Sometimes, deer mice will form a nest above ground in a hollow log or an abandoned bird's nest. When they enter an unoccupied human-made structure, they will build their nest in cupboards, or furniture. Generally, when they do invade an occupied building, they'll nest in an area as far from human activity as possible, such as attics, basements, crawl spaces and garages. Deer mice will use upholstered furniture, mattresses, clothing, paper or other similar materials to build their nests. They also have a much greater preponderancy for caching food such as nuts, berries and seeds than house mice. During the warmer months, they feed on insects, bark, fruit, seeds and roots.

Rodent-proofing is the best and most permanent method for preventing rodents from entering your home or out buildings. Seal all openings greater than the thickness of a pencil (6 millimeters). Once an opening is located by deer mice, they will gnaw to enlarge the opening so they can get in. Food such as dry pet food, seeds or grain based foods should be kept in rodent-proof containers.

Because they are hoarders, white-footed mice will carry off more poisoned bait than a house mouse. For this reason, bait blocks, as opposed to loose bait, may be more effective.

Ordinary mouse traps work well for white-footed mice. Bait the traps with moistened oatmeal or with peanut butter and place them against walls. Like most rodents, deer mice prefer to travel along a wall when they're active because of the added protection it affords them. If you want to use a live trap and release the mouse back into the wild, go ahead. Just remember, deer mice are the most common food item on the list of every carnivore from black bears to snakes and, without a place to hide, it will be something's lunch. If, by some miracle, it does manage to survive, recent research done in Texas found that deer mice have an excellent sense of direction and were documented returning to their original point of capture after being released over 3 kilometers away. Whatever you plan to do or not do, they will return to their preferred habitat outside come spring.

Tim Lockley, a specialist in entomology, is retired from a 30-year career as a research scientist for the U.S. Department of Agriculture. For answers to individual questions, please send a stamped, self-addressed envelope to Tim Lockley, c/o Sun Herald, P.O. Box 4567, Biloxi MS 39535.

This story was originally published January 14, 2016 at 5:33 PM with the headline "TIM LOCKLEY: Deer mice might try to come in from the cold ."