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Photo Credit: Clemson University
SCIENTIFIC NAME: Permyscus polionotus
OTHER NAMES: Deer mouse, beach mouse.
DESCRIPTION: Oldfield mice are rodents, members of the family Cricetidae. They are the smallest members of the genus Peromyscus in the United States. The underside of an oldfield mouse’s body and tail is pure white, with upper parts varying greatly in color with individuals from different populations. Inland populations range from dark brown to cinnamon in color while coastal populations tend to be very light tan to almost white. This difference in coloration is closely correlated with the color of soil and/or leaf litter in the area in which they live, presumably allowing them to better blend into their background. In all populations there is a clearly defined line between darker upper parts of the body and white underside of their body and tail. The paws of oldfield mice are white. Oldfield mice range from 4.8-6.0 inches long and weigh 0.35-0.60 ounces with males typically smaller than females. Their tails are short, usually only 55-65% of the length of their bodies. Oldfield mice have keen senses of hearing, vision, touch, and smell. Chemical cues (pheremones) are believed to be used extensively in communication between and among individuals.
DISTRIBUTION: Oldfield mice are native to the southeastern United States. Their range includes portions of North Carolina, South Carolina, Tennessee, Florida, Mississippi, most of Georgia, and most of Alabama.
HABITAT: Oldfield mice inhabit a variety of diverse terrestrial environments. They typically occupy habitats in early successional stages such as scrub habitats, abandoned fields, beach dunes, and coastal islands. Populations are found in areas having well drained loamy or sandy soils. They are not found in areas having hard packed or poorly drained soils because dry, sandy soil is necessary for the construction of their characteristic burrows.
FEEDING HABITS: Oldfield mice have been described by some as granivores (feeding almost exclusively on seeds. In reality, however, they are carnivore-omnivore rodents although the majority of their diet is composed of seasonal seeds. Oldfield mice readily consume a wide variety of foods, including seeds, acorns, insects and other invertebrates, and even small vertebrates. They have been shown to prefer animal foods over most seeds when given the choice. Oldfield mice are hoarders, storing large quantities of seeds in their underground burrows for later use. It is believed that significant competition may exist between these mice and harvester ants (Pogonomyrmex spp.) that collect and store seeds of the same species.
LIFE HISTORY AND ECOLOGY: Oldfield mice are almost exclusively nocturnal with greatest levels of activity occurring on cloudy or moonless nights. They are excellent diggers, constructing extensive burrow systems extending from 1-3 feet below ground level. These burrows have two access points. The burrow entrance will have a distinctive fan shaped mound of dirt at its mouth, while the escape tunnel will usually be much harder to find, in that the soil removed during its construction is deposited on the entrance mound. The entrance tunnel is typically blocked near the surface with soil during the day, presumably to provide some protection from predators. Nests of dried grass and other fibers are constructed in the central chamber. Other secondary chambers may be used for food storage. As many as 20 burrows (more typically 4-6) may be constructed within a given home range. Home ranges for oldfield mice have been documented ranging from 0.10 acre to 7.25 acres. Home range size appears to be related to food availability and the availability of suitable burrow sites. Oldfield mice, especially females with litters, may defend small territories surrounding burrows in current use.
Oldfield mice are monogamous forming strong pair bonds and raising their young together. The gestation period for oldfield mice averages 28 days with females often coming into estrus again within days after giving birth. Litter size ranges from two to eight young but usually with four. Consecutive litters may be born at intervals of as little as 30 days. Young are born pink, hairless, and blind, but develop rapidly. Their eyes open by day 14 and the litter is weaned 20-25 days after birth. Females reach sexual maturity at an average age of about 30 days. Litters are born year round, but reproduction typically slows during the summer and peaks during late fall or early winter. With an average lifespan of less than nine months, oldfield mice rarely survive as long as 1.5 years, although they have been known to live more than four years in captivity.
Oldfield mice are an important food source for many small predators such as red and gray foxes, weasels, skunks, raccoons, great blue herons, owls, and numerous snake species, as well as domestic dogs and cats. They are also believed to play an important role in determining survivorship of seeds in the plant communities in which they live.
Though individual inland populations of oldfield mice may be present for only 3-5 years at a given site as succession progresses, natural disturbances are constantly creating new habitat to be colonized. Atlantic and Gulf Coastal subspecies’ (referred to as beach mice) status, however, is far from secure. Populations inhabiting beach dunes and coastal islands comprise at least seven subspecies, all of which are federally classified as either threatened or endangered. At least one additional subspecies is known to already be extinct. Habitat loss is believed to be the most important factor leading to the decline of these subspecies. A combination of beach development and water recreation are believed to compound the devastating effects hurricanes have on their coastal habitats.
“Animal Diversity Web: Peromyscus polionotus (oldfield mouse)”Http://www.animaldiversity.ummz.umich.edu/site/accounts/information/Peromyscus_ polionotus.html
Gentry, J.B. and M.H. Smith. 1968. Food Habits and Burrow Associates of Peromyscus polionotus. Vol. 49, No. 3, pp. 562-565. Journal of Mammalogy.
“Peromyscus polionotus, Oldfield mouse. By: Michael C. Wooten” Http://Wotan.cse.sc.edu/perobase/systematics/p_polion.htm
“Smithsonian National Museum of Natural History, North American Mammals, Peromyscus polionutus, Oldfield Mouse” Http://www.mnh.si.edu/mna/image_info.cfm?species_id=262
Author: John S. Powers, Wildlife Biologist, Division of Wildlife and Freshwater Fisheries