Deer Mice: More Than Just a Carrier of Lyme Disease

The deer mouse first became widely known because of its role in the transmission of hantavirus and as a reservoir for Lyme disease, but it has become an important indoor mouse pest in many areas of the United States. It is found throughout most of Canada and the U.S. except for a few southeastern states.

The deer mouse, Peromyscus maniculatus, is hard to tell apart from the closely related white-footed mouse, Peromyscus leucopus, and the term “deer mouse” is often used for both. Because the deer mouse and the house mouse are similar, we’ll concentrate on how their differences.

Most notably, the deer mouse has a two-tone coloration, usually a tawny brown (sometimes gray) on its back with a pronounced dividing line between its white belly, with white feet and white on the bottom of its hairy tail. The mostly gray house mouse has a mostly naked tail. The two mice are about the same size, but the deer mouse has larger, prominent eyes and larger, thinner ears than the house mouse.

Outdoors, deer mice will nest around the roots of trees, under boards or logs, in stumps or woodpiles, in animal burrows or bird nests, in sheds or in abandoned vehicles or equipment. Deer mice are active year-round, mostly at night, and can damage garden crops.

ROLE AS A STRUCTURAL PEST. Deer mice are good climbers and use vines and tree limbs to reach attics or upper levels. Favorite indoor nest sites are drawers and storage cabinets in garages, items stored in attics, upholstered furniture, wall voids and corner sill plates in basements and crawls.

These mice feed on a variety of foods but particularly like seeds and nuts and will cache large amounts near their indoor nests. Deer mice urinate and defecate in their nests and will build a new nest when the current one becomes too foul. Hantavirus is a concern for people in dusty environments with a large amount of deer mouse urine and droppings.

Deer mice indoors are controlled in the same way as house mice. Baited snap traps work, as do rodenticide baits. Use secured block baits and avoid loose baits because of the deer mouse’s habit of hoarding without eating. Make sure deer mice are listed on the label.

POINTS TO REMEMBER. The deer mouse is the most common small mammal in North America and is generally seen as more of a rural, outdoor mouse, occasionally found in sheds, cabins or barns. But it has become increasingly common in homes, especially those surrounded by natural habitats. Deer mice often move in with cooler fall weather.

The authors are well-known industry consultants and co-owners of Pinto & Associates.