As cute as it appears to be, the deer mouse (Peromyscus spp.) can be a very deadly creature. This innocent-looking little rodent is the primary spreader of hantavirus, which causes very serious disease.
Called a deer mouse because it somewhat resembles a very small deer, this mouse's upper body is grey to reddish-brown, its underbelly and legs are white, and its tail has two colors: dark on top and white on the sides and bottom. With big eyes and prominent, leaf-like ears, the deer mouse is a deceptively cute creature.
All rodents are capable of spreading disease-causing pathogens of different sorts, but the deer mouse is notorious as a spreader of hantaviruses, which can cause a particularly deadly respiratory illness. Thus, getting rid of an infestation of deer mice, and denying them entry to your home, is a serious matter.
3 Ways to Get Rid of Deer Mice
Many of the same control measures used for common house mice will also work for deer mice, but care must be taken to avoid physical contact with the mice, as well as their feces, urine, and saliva, where hantavirus is most likely to dwell.
Since deer mice are typically outdoor dwellers that seek indoor shelter only when cold weather approaches, prevention and control measures often focus on outdoor areas and on blocking entry points into the home.
Encourage Natural Predators
A variety of wild predators can help control deer mice populations around your home. Deer mice prefer outdoor locations, so they are especially susceptible to predators.
Owls and other raptor species of birds are prodigious hunters of mice and other small rodents, as are a variety of snakes and hunting mammals, such as foxes and coyotes. If you live in an area where such hunting creatures exist, they shouldn't be feared, but rather encouraged.
Deer mice can be caught with the same types of traps used to catch ordinary house mice. If using kill traps, take care not to touch the mice with your bare hands; you may want to use a protective breathing mask and wear gloves when disposing of mice, and when cleaning up nests or droppings. Above all, avoid breathing dust that might contain dried feces or urine, which is where hantavirus and other pathogens are most likely to dwell.
Outdoor trapping is possible, but with outdoor traps, it can be hard to avoid catching other wild creatures, such as chipmunks and squirrels. If attempting to trap mice outdoors, it's best to use live traps, since you can then live-release the desirable creatures, dispatching only the mice that are caught. If using live traps, make sure to avoid being bitten by rodents.
Use Rodent Baits/Poisons
The same rodenticides used for house mice and rats will also kill deer mice dwelling in your home. But make sure to use these chemicals in a manner that protects humans and pets from accidental ingestion. And never use rodenticides outdoors, where dogs and desirable wildlife can reach them. Make sure to follow label directions when using rodenticides.
Most rodent poisons use long-acting anti-coagulants (LAACs) that disrupt the ability of blood to clot. Call a veterinarian or emergency room immediately if a pet or human ingests these poisons.
What Causes Deer Mice?
Like many other rodents, deer mice seek areas where there are sources of food and water and shelter from the elements. Unlike house mice, which prefer indoor dwelling year-round, deer mice are more typically outdoor feeders living on plant seeds and fruits that seek indoor shelter only when the weather turns cold.
How to Prevent Deer Mice
There are a variety of measures you can take to make your home less likely to experience deer mice:
- Seal holes and gaps in your home or garage. Deer mice very often seek indoor shelter when the weather turns cold, so inspecting and sealing gaps should be part of each year's winterizing routine.
- Clean up and/or put away exposed food to make it less attractive and less accessible to rodents (and other pests). Deer mice are especially fond of seeds, fruits, and other dried foods, so make sure to store birdseed and pet foods in sealed, impenetrable containers.
- Maintain mouse traps in and around your home to monitor rodent presence. This will help you identify if you have a deer mouse problem.
- Clean up litter and piles where rodents like to live and breed.
- Keep the areas near your home free of brush piles, tall grass, and other dense foliage where deer mice often live.
Deer Mice vs. Other Hantavirus-Spreading Rodents
Although it is the primary carrier, the deer mouse is not the only carrier of hantavirus. Other prime carries include:
- White-footed mouse (Peromyscus leucopus): Closely resembling and closely related to the deer mouse, the white-footed mouse is found in many areas of the U.S., including the eastern coast from the South up through southern New England, the Midwest, and the West, as well as Mexico. These rodents are nearly identical to deer mice, but they have distinctive white feet.
- Cotton rat (Sigmodon spp.).: With a head and body that measures 8 to 11 inches from the tip of the nose to the end of the tail, this rodent is much larger than the deer mouse. In the U.S., this rat is found primarily in the Southeast, and it prefers to live in areas that are overgrown with weeds, shrubs, or tall grass.
- Rice rat (Oryzomyini family): Though smaller than the cotton rat, the rice rat is still larger than the deer mouse. As its name hints, this semi-aquatic rat prefers wet and marshy areas like rice paddies. In the U.S., it is found primarily in the Southeast.
Frequently Asked Questions
How Does a Deer Mouse Differ From a House Mouse?
There are two predominant species of deer mice, both of which can spread hantavirus. They are nearly identical in appearance, distinguished only by the territory they occupy. The eastern deer mouse (Peromyscus maniculatus) is widespread through territory east of the Mississippi, except for lowland areas of the Southeast. The western deer mouse (Peromyscus sonoriensis) is found throughout forests and grasslands of the western U.S., including the desert regions of the Southwest. These two species were once lumped together as P. maniculatus, but are now considered separate.
The deer mouse is slightly larger than the common house mouse, about 7 inches from the tip of the nose to the end of the tail, vs. the 5-inch overall length of the house mouse. And deer mice have a notable white underbelly that extends to the underside of the tail. This white belly is not found on the house mouse, which is entirely brown or gray.
Deer mice are primarily outdoor feeders that may seek indoor shelter during cold weather, while the house mouse is more likely to be a permanent indoor dweller.
How Dangerous Is Hantavirus?
Hantaviruses comprise a number of different pathogens in the Bunyavirales order, some of which are capable of causing serious respiratory illness in humans, especially hantavirus pulmonary syndrome (HPS).
Rodents that carry the viruses do not become ill themselves, but humans who breathe in viruses found in rodent feces, urine, or saliva may develop symptoms after an incubation period lasting several weeks. Initial symptoms include fever, cough, muscle pain, headache, nausea, vomiting, diarrhea, and shortness of breath. This can quickly evolve into pulmonary edema causing fatal cardiac arrest. According to the CDC, there is a 38 percent mortality rate for individuals developing HPS, making this one of the most deadly of viral diseases.
Fortunately, hantavirus infections are relatively rare, with an average of about 25 cases reported each year in the U.S., mostly in western states. But it can be a very serious disease for infected individuals, so the presence of deer mice is cause for immediate action.
How Long Does Hantavirus Live?
Hantavirus in dust contaminated by deer mouse urine or feces is thought to live no more than a few hours, so if rodent populations are eradicated, the danger vanishes fairly quickly. Most cases of hantavirus-caused disease (roughly 600 in the U.S. since the disease was first reported in 1993) are in situations where individuals are living with ongoing nesting rodent populations.
How Is Hantavirus Spread?
Hantavirus is transmitted through the inhalation of contaminated air as well as through contact with mouse urine, feces, or the saliva of infected rodents. When cleaning up nests or dried droppings, it is wise to wear breathing protection and wear protective gloves when handling dead mice or when cleaning by hand.
Where Are Deer Mice Most Likely to Be Found?
Although the deer mouse prefers woodlands and rural areas, it will also make its home in urban areas and cities. It may live about anywhere it finds concealed nesting areas and nearby food, such as in underground burrows, brush piles, and weedy or grassy areas; under logs, stumps, or rocks; in abandoned dens of other animals, and the natural cavities of trees. Though preferring outdoor living, this rodent does seek indoor shelter when the weather turns cold.
For reasons not fully understood, most cases of hantavirus respiratory disease occur in western states, usually at higher altitudes. There have, however, been occasional cases as far east as New York, as well as in the Midwest.