DEER MOUSE

The deer mouse (Peromyscus maniculatus) is a common rodent here in Ontario, and across Canada. Deer mice (also called ‘field mice’) are nocturnal outdoor pests in rural areas, especially fields, grasslands or densely wooded areas where they can eat small insects, worms, fungi, fruit, nuts and seeds.

Deer mice are typically small rodents, but can range in length from 8 cm to 17 cm. They have large ears, huge eyes and soft tawny brown (like deer) or grey fur. Unlike the house mouse, they have a white belly and tail bottom, and white colouring on their feet. Their tail is typically the length of their body. Like other rodents, they need to constantly chew and gnaw to maintain their teeth.

While preferring to live outside in underbrush, tree cavities, shrubs, tall grasses and crevices in rocks, they do at times invade nearby homes, garages, sheds, barns, warehouses and factories. This commonly occurs in the fall when colder weather moves in, and they are searching for warm shelter, food and water. Once indoors, the deer mouse seeks refuge in basements, attics and crawl spaces where human activity is minimal. They will eat what humans do, including discarded food waste, and they create food reserves in holes close to their nesting areas.

Deer mice are a major concern to humans. They cause damage to property through biting, chewing, foraging and burrowing. They can and will chew through vinyl, wiring, insulation, drywall, plastic and books. Deer mice are one of the main carriers of hantavirus pulmonary syndrome, a respiratory disease, which is dangerous to humans. This disease is spread to humans through encountering their urine, droppings or from direct contact with live or dead deer mice. Deer mice can also transmit to humans Salmonellosis, a bacterial disease which affects the intestinal tract. Salmonellosis bacteria is common in deer mouse droppings. It is passed on to humans through contaminated food that contains infected deer mouse droppings.

Deer mice populations grow rapidly which can quickly lead to a deer mouse infestation. Active breeding occurs from March to October resulting in female deer mice birthing 2 to 4 litters a year. Litter sizes vary, ranging from 5 to 12 babies. Within 2 months post birth, deer mice are capable of breeding. The average lifespan of deer mice is 1 year; however, they can live longer if they are able to survive winter months when food is scarce and environmental conditions are harsh.

Learn the common signs of a deer mouse infestation and how to get rid of mice.