It’s the middle of winter and all is quiet in the garden…or is it? As some of the smallest mammals that inhabit our outdoor spaces, garden mice may escape our notice until they’re found snuggled into stored row cover or flowerpots, or are seen skittering across the ice to gather dropped bird feed.
The exact species varies with location, but in all temperate climates there are native woodland mice that adapt wonderfully to vegetable gardens, tool sheds, chicken coops, wood piles, and other cold yet protected spaces. In much of north America, the main garden mice are white-footed deer mice, Peromyscus leucopus. A related species, Peromyscus maniculatus, is common in western states. In Great Britain, the similar wood or field mouse (Apodemus sylvaticus) is often seen gathering seeds in the winter garden.
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A snug winter mouse nest hidden behind a closed door to a chicken coop
Mouse Nesting Habits
These woodland mice are different from less hardy house mice (Mus musculus), which have been semi-domesticated and are raised as pets and research animals. House mice are also the charming subjects of wildlife photographer Simon Dell, who set up a little village for them in his garden in Sheffield, UK.
Resourceful garden mice make the most of any shelter they encounter, including cars and houses, but they are most at home outdoors. Holes in trees make suitable homes for these agile climbers, and they often move into vacant birdhouses or pots kept on a high shelf. Last winter one built a leafy nest in an empty grow bag hung on a hook in my garden shed. It was a perfect place, high off the ground and protected from wind, yet it got full morning sun.
Garden mice are most active at night, especially just after dusk. Compulsive nest builders and food gatherers, they use straw, leaves, hair, feathers, and other materials to protect themselves from cold. Their seed-cleaning skills put humans to shame.
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Hawks and other avian predators often look for mice in late summer, when mouse populations are high
Garden Mice and Lyme Disease
Now for the bad news. Garden mice often are carriers of the bacteria that causes Lyme disease, which can be spread from mice to ticks to people and deer. It would seem that eliminating mice from an area would solve the problem, but mice are adaptive creatures. Replacements promptly appear when a good territory becomes open for occupancy.
The invasive plant called Japanese barberry can aggravate the problem. Researchers have found that Japanese barberry hosts very high numbers of Lyme-positive ticks, and mice often become infested as they harvest the dropped berries.
The best overall strategy is to keep garden mouse populations low by maintaining a good level of wildlife diversity that includes predators like owls, hawks, bobcats, foxes, snakes, raccoons and weasels, which are active at different times of year. These animals cannot host Lyme disease, so when they eat a Lyme-infected mouse, that’s the end of it. Plus, the same predators that hunt mice also eat garden voles, which are far nastier vegetable garden pests that love to sink their teeth into almost-ready root crops.
Are Garden Mice All Bad?
Yes and no. Garden mice are as willing to eat a beetle as a weed seed, caterpillar, or small songbird egg, and along with the Lyme disease problem, they can carry other diseases that infect humans. On the plus side, garden mice aerate soil with their burrowing, leaving behind little fertilizer pellets, and their abandoned nests are sometimes used by bumblebees.
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Mice like this field mouse help aerate and fertilize soil in the garden
They are staple foods for foxes and owls. Woodland mice often stay active under cover of snow, but without snow protection they are easy pickings for predators. They also have no talent for escaping when they fall through melting ice. Winter mortalities tend to be high, with only a few lucky mice surviving until spring.
Woodland mice are cute members of the garden’s natural outdoor community, but you don’t want them coming into your house. Close up small openings they might use to sneak inside, and be prepared to catch and relocate intruders captured in humane traps baited with peanut butter. They will waste no time finding a suitable home for themselves out in the garden.
