Deer mice ( Peromyscus maniculatus) are ubiquitous North American rodents known for their adaptability and diverse dietary habits. This article delves into the intricacies of their diet and foraging behavior, exploring the factors that influence their food choices, storage strategies, and overall ecological role.
General Characteristics of Deer Mouse
The deer mouse, also called the North American deermouse, is a small rodent with large, protruding, black eyes; large, scantily furred ears; long, coarse whiskers; and a moderately to well-furred tail from one-third to less than one-half of the animal’s total length with a slight tuft at the tip. There are 4 clawed toes and an inconspicuous nailed thumb on each front foot, and 5 clawed toes on each hind foot. The soles of the hind feet are thinly furred from the heel to the 6 pads, or tubercles. Small internal cheek pouches are present.
Deer mice typically measure 119 to 222 mm in length and weigh between 10 and 24 grams. They have round and slender bodies, large eyes, and sparsely furred ears. Their coloration is generally grayish to reddish-brown with white underparts, though some populations exhibit less distinct color differentiation. The hind feet of the deer mouse are usually 22 mm or more in length. The dental formula is 1/1 0/0 0/0 3/3.
Geographical Distribution and Habitat
The deer mouse (Peromyscus maniculatus) is a North American species found from Alaska and Canada southward to central Mexico. It occupies many different ecological zones throughout its range, including fields, southern montane woodland, and arid upper tropical habitats. P. maniculatus is also found on boreal, temperate, and tropical islands. They are one of the most abundant mammals on open lands. Terrestrial habitats at all elevations provide home to deermice, and ground cover harbor the largest populations.
Dietary Habits: An Omnivorous Approach
The deer mouse is omnivorous. While popular culture might depict mice as cheese-loving creatures, their natural diet is far more varied. Deer mice exhibit opportunistic feeding habits, consuming a wide range of items based on availability and seasonal changes.
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Seeds and Grains
Seeds and grains form the cornerstone of the deer mouse diet. They consume seeds from grasses, crops, and wild plants, often targeting corn, wheat, oats, and barley fields. Deer mice also gather loose grain from animal feed or leftover harvest debris.
Fruits and Nuts
Deer mice take full advantage of seasonal fruits, which provide essential sugars and hydration. They also consume nuts such as acorns, walnuts, pecans, and hazelnuts, which offer healthy fats and protein for energy.
Insects and Other Invertebrates
While primarily herbivorous, deer mice also consume insects, spiders, centipedes, millipedes, snails, slugs, worms, eggs and young of birds, and dead mice. The protein from insects is particularly important during the breeding season.
Other Food Sources
Deer mice have been known to consume mycorrhizal fungi, other fungi, leafy vegetation, fruit pits, and even carrion. They also sometimes eat their own feces (coprophagy).
Foraging Behavior: Strategies for Survival
Deer mice are primarily nocturnal, with peak activity occurring at twilight. They spend most of their time on the ground but are also adept climbers and can swim. Their foraging behavior is influenced by factors such as food availability, predation risk, and social interactions.
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Nocturnal Activity
The prairie deermouse (Peromyscus maniculatus bairdi) is strongly nocturnal on a 12:12 LD-cycle with a bimodal, dusk-dawn feeding pattern. It has been suggested for the rat that the dusk peak is more dependent on the animal's immediate energy needs while the dawn peak has an anticipatory function in storing food.
Nesting and Caching
Deer mouse activity centers around a nest and food cache. They may use abandoned dens of other mammals, but prefer natural cavities of trees. They store seeds and nuts in holes in the ground, old bird nests, or trees. These caches may contain as much as 1 pint of food. Deer mice do much of their feeding at these storehouses, carrying food in their small cheek pouches, which together hold about 1 teaspoon of seeds.
Social Behavior and Territory
Deer mice are generally solitary, but sexes and ages may huddle together in nests to conserve heat. Deer mouse home ranges vary from 242 square meters to 3000 square meters. Male home ranges are larger than females and show more overlap. Females tend to be territorial around feeding and nesting sites, especially reproductive females. Females show more defense than males.
Sensory Adaptations
Deer mice rely on their senses of smell, hearing, and vision to locate food. They also use vocal signals and make a variety of squeaky vocalizations.
Impact on Ecosystems and Human Interests
Deer mice play a complex role in ecosystems, serving as both consumers and prey. They are a staple in the diet of a wide variety of animals, including fur-bearing mammals. However, they also consume seeds of valued forest trees, sometimes preventing regrowth. Deer mice are also known to carry diseases such as Lyme disease and hantavirus (e.g., Muerto Canyon virus).
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Deer Mouse in Human Environments
Wild mice are born survivors, foraging constantly in the wild and hoarding whatever they can find to survive the harsh winters. But when they move indoors, they become more opportunistic - feasting on whatever’s available. That means sealing food, staying clean, and cutting off access points - especially in places like garages, campers, and RVs.
What do mice eat in human environments?
- Human pantry items: Cardboard boxes, paper bags, and plastic wrappers are no match for a mouse’s sharp teeth.
- Pet food: Pet food can be especially problematic because it’s often stored in large, semi-open containers or left in bowls overnight.
- Trash and scraps: They’ll lick the crumbs off dishes, eat scraps from trash bags, or make the most out of spills under appliances.
How to keep mice away
- Seal food, stay clean, and cut off access points - especially in places like garages, campers, and RVs.
- A mouse is not deterred by all the hard-to-reach places our food scraps go to die. They’ll be the first to check under the fridge, behind the trash, and in the dark corners.
- Food matters, but so does security.
- Where there’s a will (or a hole, a crack, a gap), there’s a way. Mice can squeeze through openings as small as a dime and climb up multiple stories if properly motivated.
- Even if your food is sealed and your trash is taken out, mice may still try to enter if your vehicle or garage feels safe.
Similar Species
Missouri's four species of Peromyscus mice are similar in appearance and habits. The best way to distinguish between them is by differences in size and characters of the tail. The other members of this group are the white-footed mouse (or white-footed deermouse, P. leucopus), the cotton mouse (or cotton deermouse, P. gossypinus), the Texas mouse (or Texas deermouse, P. attwateri), which closely resembles the deer mouse but is slightly larger with a longer, strongly two-colored tail that has a fur tuft at the tip; the flanks are paler than those of the deer mouse. In areas where these species occur together, their sizes can be intermediate, so they can be very difficult to identify to species. Also, keep in mind that Missouri has - in addition to members of the genus Peromyscus - about 20 other species of small mice, rats, and voles.