Golden mouse

Golden mouse Temporal range: Late Pleistocene to Recent
Conservation status
Least Concern (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Rodentia
Superfamily:	Muroidea
Family:	Cricetidae
Subfamily:	Neotominae
Tribe:	Ochrotomyini Musser and Carleton, 2005
Genus:	Ochrotomys Osgood, 1909
Species:	O. nuttalli
Binomial name
Ochrotomys nuttalli (Harlan, 1832)

The Golden Mouse, Ochrotomys nuttalli, is a species of New World mouse. It is usually 5–8 inches (12–25 cm) in body length, and has a golden-brownish color.

Geographic Range

Ochrotomys nuttalli lives and breeds in the southeastern United States.^[1]

Habitat

Golden mice, O. nuttalli, live in thick woodlands, swampy areas, among vines, and within small trees and shrubs. These animals especially like to live where honeysuckle, greenbrier, and red cedar grow. Golden mice in the south-central region of the United States inhabit climates that are hot and wet in the summer and dry in the winter.

Their nests may be located in the trees or on the ground. Ground nests, frequently located near leaf litter, may be fabricated within sunken areas of the soil or beneath logs. Ground nests have both advantages and disadvantages. Floods or wet soil may force golden mice to leave their ground nests and relocate into the trees. However, if the ground nest is undisturbed, it can lower the risk for predation for the following reasons: the nest is well hidden, a mouse on the ground is more likely to escape a predator, and less energy is required to build a nest on the ground since the mouse doesn't have to keep running up and down a tree with nesting materials.

Golden mice have been known to remodel old bird nests into homes for themselves. Otherwise these animals create a nest 100 to 200 mm in size, from scratch using different elements, depending on what materials are locally available.

The inner lining of a nest consists of soft materials such as milkweed, cotton, feathers, or fur. A thick layer of woven fibers surrounds this fluffy layer. The protective, surface material contains leaves, grass, and bark. The nest usually has one entrance, although up to fifty-seven have been noted.

Physical description

The body length of O. nuttalli ranges from 50 to 115 mm. The prehensile tail is from 50 to 97 mm in length, generally the same length as the body of the mouse to which it belongs. Golden mice receive their common name from the thick and soft golden fur that covers the upper body. However, the feet and undersides are white and its tail have a cream coloring. Regional differences occur in the amount of yellowish, reddish and brownish overtones in the dorsal pelage. About five subspecies have been described, however, all are likely representative of a regional cline rather than distinct populations. Populations from the Atlantic coastal plain of Virginia, the Carolinas and Georgia (O. n. nuttalli) are somewhat brighter (more reddish yellow); populations from the Piedont and mountainous areas to the west (O. n. aureolis) are somewhat more brownish; populations from Texas, northern Louisiana, Arkansas, Missouri and Illinois (O. n. lisae and O. n. flammeus) have more yellowish overtones; populations from the Florida peninsula (O. n. floridanus) are rich yellowish-brown.

Male golden mice have a baculum tipped with cartilage. Females have six mammae.

The cheek teeth of golden mice contain thick folds of enamel. As in other members of Muroidea, these mice have an infraorbital foramen with a distinct keyhole shape. Neither canines nor premolars are present. Incisors are sharp and long, separated from the cheek teeth by a diastema.

Because of their attractive golden colour, golden mice have often been used in books, such a Ragweed, Poppy, Poppy and Rye, Ereth's Birthday and Poppy's Return. (see Edward Irving Wortis)

Diet

Golden mice are granivorous, eating mostly seeds. They prefer sumac seeds, but also consume honeysuckle and other seeds as well. Sumac seeds are poor quality food because they contain tannin, which reduces the efficiency of enzymes in the mouse's digestive pathway. Studies have shown that females fed year-old seeds, which have more calories, have significantly higher mean ingestion and assimilation rates than females that eat freshly matured seeds.

Flooding is a problem for golden mice because the water causes the seeds to be unobtainable, to sprout, or to spoil.

Reproduction

Golden mice reproduce all year long. However, the reproductive season varies geographically. The majority of O. nuttalli reproduce from September to spring in Texas but from March to October in Kentucky and Tennessee. Golden mice in captivity tend to reproduce most frequently during the early spring and late summer. Because the gestation period is only about 30 days, females can produce many litters in one year. Captive mothers have been known to produce up to seventeen litters in an eighteen month period. A litter of golden mice typically consists of two or three young, but ranges from one to four. Aside from the mother, all other adults leave the nest when the litter is born.

Behavior

Ochrotomys nuttalli is mainly nocturnal and arboreal, although many live on the ground as well. Golden mice move quickly and easily. They are able to use their prehensile tails to balance while climbing trees and also to hang from branches.

Ochrotomys nuttalli is a gregarious creature. In fact, up to eight mice have been discovered sharing a nest at one time. Groups can consist of kin or unrelated individuals. The most common groups consist of mothers and their young. Many scientists speculate that living in groups conserves energy. This idea is supported by the observation that mice are found in groups more often in the winter when such grouping produces a clear cut thermoregulatory benefit.

Golden mice have a low basal metabolic rate and high conductance. When their areas become flooded, golden mice activity is significantly reduced.

Ochrotomys nuttalli in captivity has displayed submissive behavior.

References

1. ^ ^{a b} "Ochrotomys nuttalli". IUCN Red List of Threatened Species. Version 2009.2. International Union for Conservation of Nature. 2008. http://www.iucnredlist.org/apps/redlist/details/42674. Retrieved 2010-01-29.