The Wood Rat:

A Furry Friend From the West

by Chris Grondahl

North Dakota Outdoors Feb. 1995

Our environment is full of enough different creatures to always keep us humble. Just when a person thinks he knows a little about everything, he discovers otherwise.

Until recently, the bushy-tailed wood rat was one of those creatures I had not discovered, though I was likely close to them on several occasions.

Most North Dakotans will probably never see a bushy-tailed wood rat, though you are probably familiar with them under their nickname, the "pack rat." They live only in western North Dakota, primarily the badlands, and they are usually active only at night.

The bushy-tailed wood rat is a large, handsome rodent. It grows to about eight inches long, with another six inches of "bushy" tail. The body is primarily pale grayish to buff with a white belly and feet. The tail is dark gray on top and white toward the bottom.

This small mammal species is found mostly in the western mountains from Alaska to Arizona and from the western parts of the Dakotas and Nebraska to the Pacific Coast. It is found almost exclusively in rocky areas. In North Dakota's badlands, this means rocky outcroppings or cavernous sandstone formations including deep crevices, cracks and small caves.

Wood rats may also live in abandoned buildings located near rocky habitat. In such locations, wood rats will build large stick houses that may incorporate just about any object in the vicinity that they can carry - such things as bones, conifer cones, bits of rope, leather, hide, paper, shingles, wire, bottle caps, feathers and shotgun shell cases. Ironically, mouse traps have also been discovered in these collections.

From this collecting instinct, the bushytailed wood rat earned the pack rat nickname. It is also called "trade rat," referring to its habit of picking up a new object before the one they were carrying is stashed.

The house, sometimes referred to as a midden, protects the rat from weather and enemies and is the center of activity. This area is defended against other wood rats.

Breeding occurs in May or June. Wood rats build a nest with dry grass, bark, moss and leaves. After about five weeks, three or four young are born. Since the species is solitary, the young disperse away from others and build their own houses or remodel those used by earlier generations.

The wood rat is active year-round, feeding during winter on vegetation stored during the previous fall. Diets vary, but wood rats will eat just about any plant that grows in their territory.

Predation occurs mainly from coyotes, long-tailed weasels, bobcats and owls during the night when rats are most active.

Bulging eyes and relatively large scoop-like ears aid the wood rat in its nocturnal habits. Because of this lifestyle and remoteness of their habitat, human interaction is quite limited. Most often, rat droppings near the entrance of a den are the only evidence left for a trained eye in search of this species.

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Chris Grondahl is a biologist with the Department's natural resources division

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Last modified Sept. 23, 1995