Endemic to North America, the Deer mouse is one of the most common organisms of the biotic community in nearly all woodlands throughout the continent. However, even the most attentive observers often cannot spot this cryptic animal in its woodland habitat, since it’s generally active at night. The species is so called due to its deer-like coloration: the back is tawny brown, the dorsum is a camouflaging brown, while the underbelly, legs and tail are white.
This animal is native to North America, where it occurs throughout the continent, the northern tree line in Alaska and Canada southward to central Mexico, except for the southeastern United States and some coastal areas of Mexico. The preferred habitats of the Deer mouse are prairies, bushes and woodlands, although this mouse can be found in a wide variety of environments such as alpine areas, northern boreal forests, deserts, grassland, brushlands, agricultural fields, southern montane woodlands or arid upper tropical habitats. In addition, the animal inhabits some boreal, temperate and tropical islands.
These mice are highly social animals, gathering in groups that consist of a single adult male, a few adult females as well as several young individuals. In order to keep warm during the cold winter months, the deer mice huddle together in groups, composed of over 10 individuals or both sexes and various ages. In addition, during this period of the year, they keep warm and reduce the temperature of their bodies by undergoing daily torpor. The deer mouse is mainly terrestrial, though the animal is also an accomplished climber. Populations in prairie habitats usually build their nests just below the surface. They may either burrow a nest by themselves or use one, constructed by another animal. On the other hand, those in forests built their nests near the ground, typically in stumps, logs, brush piles, tree cavities, reconstructed bird nests, tree bark, sometimes using cottages and outbuildings. The deer mice are generally nocturnal animals, spending their active hours around these nests and food cache.
As omnivores, the deer mice consume a wide variety of food, including plants such as seeds, fruits, flowers and nuts as well as invertebrates such as insects. They are also known to feed upon their own feces on occasion.
Deer mice can be either polygynous, where each male mates with multiple females, or polygynandrous (promiscuous) with individuals of both sexes having multiple mates. Deer mice may breed at any time of the year with peak period, taking place during the warmer season of the year. Females of this species are able to breed again while suckling the offspring from the previous litter. Hence, duration of pregnancy depends on whether a female is lactating or not. Usually, gestation lasts 22 - 25 days in non-lactating females and 24 - 30 days in lactating ones. The size of a litter depends on population. It usually increases with each litter and begins to decrease after the 5th or 6th litter. A single litter may consist of up to 11 young with an average of 4 - 6. Newborn babies of this species are altricial. However, they develop very quickly, opening their eyes at 15 days old. Weaning occurs after a short while - at 25 - 35 days old. The age of sexual maturity is 49 days old for males and 35 days old for females.
The deer mice are nowadays quite common and widespread throughout their range, although it’s known that winter starvation leads to a high number of mortality in this species.
According to IUCN, the deer mouse is widely distributed and extremely abundant in some habitats but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) and its numbers remain stable.
The deer mouse is an important seed disperser of its range, helping numerous plants spores of mycorrhizal fungi survive. At higher trophic levels of their range, this animal is the major prey species for local predators.