DAKOTA NATURAL HERITAGE

THE WOODRATS

By Eileen Dowd Stukel

Click for link to photos of the eastern woodrat and the bushy-tailed woodrat

The list of species monitored within the South Dakota Natural Heritage Program is long and varied. Some species are tracked because they are listed as state or federal threatened or endangered species. Other monitored species are rare in South Dakota but common elsewhere. Still others are monitored because little is known about where they live, how common they are, or perhaps whether they even occur in South Dakota. Such is the case with the eastern woodrat (Neotoma floridana).

The eastern woodrat’s characteristic habitat is eastern deciduous woodlands, although it ranges as far west as eastern Colorado. This species superficially resembles two non-native or exotic rats that infest houses and other buildings, the Norway rat and black rat. These "house" rats have scaly tails, contrasted with the eastern woodrat’s hairy tail. Its soft, fine hair is brownish, except for its white throat, belly, and feet. The tail is dark above and white below.

The eastern woodrat has also been confused with South Dakota’s common woodrat species, the bushy-tailed woodrat (Neotoma cinerea) of western South Dakota. This species has larger ears and a bushier tail than the eastern woodrat, and the soles of its hind feet are fully furred. The bushy-tailed woodrat occurs in rocky, mountainous areas of western North America. They inhabit cracks and crevices of rocky sites, canyon caves, rock slides, and abandoned man-made structures. Western North and South Dakota form the easternmost extension of its range, which extends westward to the Pacific Coast and farther north than any other species of woodrat.

In constrast with the bushy-tailed woodrat’s familiar presence in suitable western South Dakota sites, the status of the eastern woodrat is much more mysterious. Over the years, people have reported eastern woodrats in South Dakota and even collected specimens they believed to be eastern woodrats. Upon examination by experts, however, no known specimens or suitably-documented records exist for the eastern woodrat in South Dakota. Although South Dakota would appear to be well away from this species’ known range, an eastern woodrat population is found nearby, along the Niobrara River in north-central Nebraska.

People are sometimes called pack rats because of a tendency to save seemingly worthless or useless objects. The name pack rat is commonly applied to all woodrats, which share a habit of collecting odds and ends, often incorporating them into their house. Another nickname is trade rat, because of the woodrat’s tendency to drop or trade the item it carries for a new treasure.

The house is the center of activity for these solitary mammals. The woodrat’s house affords protection from weather and predators. Spiny plants and plant parts may be used as building components, in addition to dry twigs and grass, bark, leaves, feathers, paper, and small stones. A woodrat may situate its aboveground home within a brush pile, below a rock shelf, at the base of a tree or shrub, or atop a man-made rafter or shelf. Within the house are tunnels, passages, and chambers. One of the chambers contains two or more nests made of woven grass, fur, feathers, and shredded bark. Other chambers are used for feeding and food storage. An individual may spend its lifetime associated with one house, to which it regularly adds fresh materials.

Both eastern and bushy-tailed woodrats are solitary, mostly nocturnal rodents that are active throughout the year. Woodrats are territorial, defending their houses and small foraging areas against others. Their vegetarian diets may include leaves, roots, bark, fruits, and mushrooms. The bushy-tailed woodrat consumes needles and cones of coniferous trees, often leaving large piles of gnawed conifer cones as evidence. Another sign of long-term bushy-tailed woodrat presence is a black, tarlike varnish resulting from continued use of its latrine area.

The bushy-tailed woodrat breeds during the spring and summer. A female may bear 2 to 3 litters per year. Following a 4- to 7-week gestation period, she bears a litter averaging 3 to 4 young. Young leave the nest at about 2 months of age, and some individuals may live as long as 3 to 4 years. The eastern woodrat may breed throughout the year in the southern parts of its range, but during the spring and summer elsewhere. The female may also bear 2 to 3 litters per year of as many as 6 young per litter. Although weaned at 3 to 4 weeks, young eastern woodrats do not attain adult size until about 8 months old. Females as young as 5 to 6 months old may breed. During dispersal, young often encounter and claim unoccupied woodrat houses as their own.

Woodrats are interesting and harmless creatures, unless they happen to "trade" for your car keys or another important possession with something of value in the woodrat’s world. These species help us broaden our understanding of nature by demonstrating that the name "rat" means much more than we may have thought. The uncertainty about whether the eastern woodrat occurs in South Dakota illustrates how little we sometimes know about our native fauna. Does South Dakota have just one species of woodrat or perhaps two? Maybe you can help solve this mystery!

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