Rodent Species Identification
Deer Mouse: Identification and Behavior
Peromyscus maniculatus
A field guide to identifying deer mice, understanding the hantavirus risk, and treating rural and suburban infestations safely.
How to Identify Deer Mouse
UC IPM says deer mice received their name because of their agility. Adults are about 3 to 4 inches long, not counting the tail, which is relatively long and sometimes as long as the head and body. They weigh about 0.5 to 1.1 ounces. Compared with house mice, they have larger eyes and ears.
The easiest feature to check is the sharply bicolored tail. Peromyscus mice have brownish upper parts, white feet and usually white undersides, with a distinct line between the brown back and white belly. Young deer mice have a blue juvenile coat and reach sexual maturity before they lose it.
Deer mouse droppings are similar to house mouse droppings, which average 1/4 inch. Location can help. Deer mice often enter vacated homes, cabins and other structures.
About 6.7 inches on average, tail included
- Compared to a house mouse:The bicolored tail is the easiest way to tell them apart
- Compared to a vole:Much longer tail than a vole
Distinguishing From Similar Species
- vs House Mouse: House mice are uniform gray-brown. Deer mice show a sharp break between brown back and white belly.
- vs White-Footed Mouse: A separate Peromyscus species that is hard to tell apart from the deer mouse. ICWDM says all Peromyscus species cause similar problems and require similar solutions.
- vs Vole: Common voles have short tails; deer mice have relatively long, bicolored tails.
Where Deer Mice Live
The deer mouse is found throughout most of North America. ICWDM notes that deer mice are uncommon in urban or suburban residential areas unless there is considerable open space, such as fields or parks, nearby.
Outdoors they nest under rocks and logs or in burrows made by other rodents. Indoors they nest in cupboards and furniture of unoccupied buildings.
Home entry follows the same small-gap pattern as house mice. ICWDM advises sealing all openings larger than 1/4 inch wide.
Deer Mouse Behavior
Deer mice are almost strictly nocturnal. Texas Tech notes they leave their daytime retreats early in the evening and stay out until shortly after sunup.
Mated pairs usually stay together during the breeding season. Females may have 2 to 4 or more litters a year, usually of 3 to 5 young, fewer than the 5 to 10 litters a house mouse may have.
Deer mice are primarily seed eaters. They also eat fruits, insects and insect larvae, and fungi. They often store food near their nest sites, particularly in the fall, and they are more likely to cache food than house mice.
Damage Deer Mice Cause in Homes
Deer mice can cause considerable damage to upholstered furniture, mattresses, clothing and paper, which they use for nesting.
Health Risks From Deer Mice
Deer mice are the primary reservoir for hantavirus pulmonary syndrome in the US. They are the principal reservoir of Sin Nombre virus, which people can catch by breathing contaminated dust after disturbing or cleaning rodent droppings or nests. Hantavirus cases are concentrated west of the Mississippi River. CDC cleanup guidance says to open doors and windows for 30 minutes first, wear rubber or plastic gloves, not to sweep or vacuum, and to soak droppings with 1 part bleach to 9 parts water for 5 minutes. For heavy infestations, CDC calls for a half mask air-purifying (or negative-pressure) respirator with a high efficiency particulate air (HEPA) filter.
CDC ties lymphocytic choriomeningitis (LCM) to the house mouse.
Any cabin or outbuilding with rodent activity where deer mice live is worth cleaning with these precautions, whether or not the species has been confirmed. Heavy contamination in an enclosed space is a job for a professional with that equipment.
How Deer Mice Enter Homes
Deer mice can use openings larger than 1/4 inch, the same threshold ICWDM gives for house mice. Because deer mice often enter vacated homes, cabins and other structures, inspection should cover outbuildings as well as the house.
Places worth checking include foundation cracks, rim joist gaps, basement window frames, utility penetrations, garage thresholds, ridge vents, attic louvers, and floor-to-wall gaps in older cabins.
Deer mice often move into vacated buildings, so seasonal cabins are worth inspecting before they are closed for the season and again when they reopen.
Deer Mouse Control Considerations
Deer mouse control puts cleanup sequencing first because of hantavirus risk: heavy contamination should be treated before extensive trapping or structural work to limit aerosol exposure for occupants and technicians.
Traps go in attics, basements, and outbuildings where activity shows, baited with seeds, since deer mice are primarily seed eaters. On rural properties, exclusion extends past the house to outbuildings, with 1/4 inch hardware cloth on attic louvers, ridge vents, crawl space vents, and cabin foundation gaps.
Mouse Control has a section on deer mice and hantavirus that explains why droppings are soaked with disinfectant rather than swept or vacuumed.
Call to get a trusted local pro out for deer mouse control.
Get HelpWhere Deer Mice Are Found
The eastern range is patchy. New Jersey health guidance says deer mice may occur in the far north of that state; the Maryland rodent manual limits them mostly to the central, northern and western parts of Maryland; and in Virginia the cloudland deer mouse occurs only in the mountains, while the prairie deer mouse is listed as uncommon in the Shenandoah Valley. In Texas, Texas Tech calls the species statewide but uncommon in the eastern, coastal and southern parts of the state.
The white-footed mouse, a separate Peromyscus species, is common throughout New Jersey and found throughout Maryland. CDC reports that 94 percent of US hantavirus cases occurred west of the Mississippi River.
Signs You Have a Deer Mouse Problem
Small droppings in cabins or outbuildings
Size alone will not separate deer mouse droppings from house mouse droppings; ICWDM says the signs of the two are similar, and house mouse droppings average 1/4 inch. Location helps: deer mice often enter vacated homes, cabins and other structures.
Stored food caches
Deer mice have a greater tendency to cache food than house mice, often near their nest sites and particularly in the fall.
Nests built from fine shredded material
Deer mice shred upholstered furniture, mattresses, clothing and paper for nest material, and they nest in cupboards and furniture of unoccupied buildings.
Similar Species and Commonly Confused Rodents
Related guides: How to Get Rid of Mice in Walls.
Common Questions About Deer Mice
Yes. Deer mice are the principal reservoir of Sin Nombre virus, a hantavirus that causes hantavirus pulmonary syndrome. People can be infected by breathing contaminated dust after disturbing or cleaning droppings or nests. Before cleanup, CDC says to open doors and windows for 30 minutes, wear rubber or plastic gloves, and never sweep or vacuum. For heavy infestations it calls for a half mask air-purifying (or negative-pressure) respirator with a high efficiency particulate air (HEPA) filter.
Sources and Further Reading
Sources for deer mouse facts on this page:
- About Hantavirus (Centers for Disease Control and Prevention (CDC))
- Reported Cases of Hantavirus Disease (Centers for Disease Control and Prevention (CDC))
- How to Clean Up After Rodents (Centers for Disease Control and Prevention (CDC))
- About Lymphocytic Choriomeningitis (Centers for Disease Control and Prevention (CDC))
- Pest Notes: Deer Mouse (UC Statewide IPM Program (UC IPM))
- Deer and White-footed Mice (Internet Center for Wildlife Damage Management (ICWDM))
- Deer and White-footed Mouse Biology (Internet Center for Wildlife Damage Management (ICWDM))
- Deer and White-footed Mouse Damage Identification (Internet Center for Wildlife Damage Management (ICWDM))
- Deer and White-footed Mouse Damage Prevention and Control (Internet Center for Wildlife Damage Management (ICWDM))
- House Mice (Internet Center for Wildlife Damage Management (ICWDM))
- House Mouse Damage Identification (Internet Center for Wildlife Damage Management (ICWDM))
- House Mouse (UC Statewide IPM Program (UC IPM))
- North American Deermouse (The Mammals of Texas, online edition) (Natural Science Research Laboratory, Texas Tech University)
- Hantavirus Infection and Hantavirus Pulmonary Syndrome (disease chapter) (New Jersey Department of Health, Communicable Disease Service)
- Rodent Control: Maryland Pesticide Applicator Training Manual, Category 7D (Maryland Department of Agriculture, Pesticide Regulation Section)
- Mammals in Virginia (465-314) (Virginia Cooperative Extension, Virginia Tech)
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