Common Name: Deer Mouse
Scientific Name: Peromyscus
Although all species in the genus Peromyscus are often referred to as deer mice or white-footed mice, the other species all have different common names except for P. maniculatus. Deer mice are structural pests in rural, summer/vacation, outbuilding, and shed-type structures, as well as suburban homes located in or near wooded areas. They are of medical concern because they are the primary carriers of hantavirus which causes hantavirus pulmonary syndrome (HPS).
The deer mouse is found in the West from Mexico to the southern Yukon and Northwest territories of Canada, and in the East from Hudson Bay south to Pennsylvania, the southern Appalachian mountains, central Arkansas, and central Texas.
Adults with head and body length about 2 3/4-4″ (7-10.1 cm), tail length about 2-5″ (5.1-12.7 cm), and hind foot 5/8-1″ (1.6-2.5 cm) long; with about 3/8- 1 1/4 oz (10.6-35.4 g); woodland forms (primarily northern) usually larger, with tail longer and feet larger than prairie/field form (primarily prairies and midwest). Bicolored, pale grayish buff to deep reddish brown above and white below.
Tail always sharply bicolored, longer than half length of head and body combined, and covered with short hairs/fur. Hind feet with 6 pads each. Young similar but top/upper side gray. Note that separation of species of Peromyscus is difficult, often requiring the services of a rodent taxonomist, but the characteristic of being bicolored with hairy tail will easily separate them from the house mouse, Mus musculus Linnaeus.
(1) White-footed mouse (Peromyscus leucopus) with tail shorter than woodland form and tail and hind feet longer than prairie/field form.
(2) Old field mouse (Peromyscus polionotus) with color whitish to fawn above and white below and tail shorter.
(3) Canyon mouse (Peromyscus crinitus) usually with tail longer and tail with tufted tip.
(4) Brush mouse (Peromyscus boylii) with tail equal to or longer than head and body combined.
(5) California mouse (Peromyscus californicus) much larger, head and body combined 3 3/4-5″ (9.5-12.7 cm) long, yellowish brown to gray mixed with black above, and tail not distinctly bicolored.
Females usually have 3-5 young per litter (range 1-8). The gestation period lasts for 21-24 days. There are 2-4 litters per year with the surge of reproduction occurring in the spring. They begin to breed at 5-6 weeks of age. The life span is 2-24 months because of high predation, but 5-8 years in captivity. Deer mice are of medical concern because they are the primary source of hantavirus which causes Hantavirus Pulmonary Syndrome (HPS). This virus is transmitted primarily by the inhalation of dust particles contaminated with the urine and/or feces from infected deer mice.
The incubation period of this disease is up to 30 days. If death is to occur, it will happen within about 12-35 days after contracting the disease and it will be the result of the lugs filling with fluid and/or a heart attack. As of 10/96, there have been 153 recorded cases of HPS in United States with a fatality rate of 40% since 1/94 (overall rate is 50%).
Deer mice are nocturnal. Their runways are poorly defined and they often use the runways of other small mammals. They are excellent climbers and can utilize the upper areas of buildings, etc. Outside, they nest in old fence posts, tree hollows/cavities, log piles, abandoned bird/squirrel nests and animal burrows, beneath decks, or dig small burrows. Inside, they nest in storage boxes, stuffed furniture, wall voids, on sill plates, in structural corners, and tight places in basements and attics. They feed on insects, seeds, nuts, berries, small fruits, a subterranean fungus (Endogone), and other small animals such as centipedes. Food is stored for the winter in hollow logs and other protected places. Deer mice have a home range of 1/2-3 acres (0.2-1.2 ha).
A summer population of 10-15 per acre (25-38 per ha) is high and some congregate in winter. During the colder months, they frequently enter homes, garages, sheds, and occasionally stored RVs and other infrequently used vehicles. They may damage food stuffs and furnishings. In unoccupied summer and vacation homes, the damage to upholstered furniture which they use for nests or nesting materials can be extensive. Deer mice are rarely a problem in urban or residential areas unless the homes border on wooded areas, such as parks. They are common in farming/rural areas and rustic suburban areas.
The key to any mouse control program is pest identification (to Peromyscus is sufficient), sanitation, harborage elimination, and mouse-proofing the building. If deer mice are already in an occupied structure, they can easily be controlled via baited snap traps placed in corners, along walls, and behind objects. Virtually any technique used for house mouse control will work. In unoccupied structures rodenticide baits work well but only a few are labeled for deer mice. Exclusion is the best control method. Seal all entry holes with 1/8″ (3 mm) hardware cloth.
Pay particular attention to any hole that is about the diameter of a pencil. If the structure has deteriorated due to lack of maintenance and/or age such that exclusion is impractical, then consider trapping the deer mice on the outside perimeter to reduce the probability of invasion. To reduce structural attractiveness, store bird seed and dry pet foods in area other than the garage or storage sheds. Because deer mice are the primary carriers of hantavirus, it is prudent to practice minimal safety precautions. These include: