The bushy-tailed wood rat, otherwise locally known as the pack rat is the only native rat found in Canada. This large, gentle and squirrel-like rodent is immediately distinguished from the introduced Norway and roof rats by its bushy tail.
Adult fur coat is long, soft, dense, usually grey on the back and with tawny brown sides, the undersides and feet are white. Males are 8 to 10% larger than females, measuring about 28 to 46 cm (11″ to 18″) in length. Tail length can be 10.5 to 22 cm (4″ to 8-3/4″) and weight can be 211 to 526 grams (7.4 to 18.4 oz).
Wood rats are active all year and primarily solitary and nocturnal, being most active during the first half hour after sunset and again before dawn. One individual to 20 acres is an average density in its preferred habitat with their presence characterized by a large bulky residence composed of twigs, bones, foliage, debris and all manner of human artifacts, some containing up to three bushels of material. Their actual nest is situated in the center of this mound, and is made of shredded bark, grass and moss – if in human environments, soft, shredded cloth, cotton batting, wool, etc. are used. The nest itself is tidy but nearby are the toilet areas, where the waste stains and cements loose debris to the rocks.
For food, wood rats prefer the leaves of aspen, willows, roses, cherries, currants, snowberries and elderberries and will also eat the twigs and needles of Douglas fir, Alpine Fir, Englemann Spruce and Junipers. They also use the seeds and fruit of Douglas fir, anemones, gooseberries, cinquefoils, raspberries, fireweed, gentians, elderberries, honeysuckles and goldenrod. In autumn, they are provident, collecting and curing the available food items, stockpiling them in crevices and under large boulders for winter needs.
Beginning in February, a male will meet with a female and pursue her until they mate in March. Gestation period is 27 to 32 days and after the young are born, the dominant female drives out the male. Litter sizes are one to six with the average at three and a half. Under favourable conditions two litters about two months apart are produced, but in the northern part of its range, usually only one. The young are weaned at 26 to 30 days and reach maturity when about eleven months old.
Distribution within British Columbia
Most literature reports that the bushy-tailed wood rat is found throughout all of BC’s mainland and is absent from the coastal islands. Some authors, however, report that this rodent is also absent from the northeast and northwest corners of the province, it is however, very predominant in the Kootenay Region. This rodent is not considered to be in jeopardy and is therefore not protected (Stevens and Lofts 1988).
The bushy-tailed wood rat requires habitat that offers security with good cover provided within rocky habitats such as talus slopes, caves, cliffs, river canyons and rock outcrops in open forests. In the absence of rocky habitat, security cover can be provided by logging slash, hollow logs, abandoned buildings and mine shafts, suitable sites for building their “stick” houses.
Wood rats owe their nickname of pack rat because of their association with stick houses which are generally quite large (1 to 1.8 m in height) and built out of woody debris, dried vegetation and other objects collected, including human artifacts such as silverware, jewelry and clothing. These houses are preferably situated within the shelter of a rocky overhang, but can sometimes be found in the open, up a tree, or in the attic space of an unfortunate homeowner.
Although often referred to as stick houses, the large piles function more as a storage dump than a house. Their true nests are small (about 15 cm in diameter), cup-shaped, and are made up of finely shredded bark and other soft materials such as fur. These nests may be found within the larger stick house but are more commonly found in a sheltered spot nearby.
The wood rat is an omnivorous rodent that will make a meal out of a variety of plants, insects, small amphibians and carrion. The majority of the wood rat’s diet is comprised of green and dry vegetation with preference shown for the foliage of herbs, shrubs and trees, but not grasses. They also feed on the vascular tissues of Douglas fir, Sitka spruce and western hemlock; willow leaves are also a favoured food. Bushy-tailed wood rats stockpile large quantities of dried vegetation to sustain them throughout the winter months.
Daily Activity and Movement Patterns
The bushy-tailed wood rat is nocturnal in activity, but can be observed occasionally during the day; they rarely venture far from the nest. Although the bushy-tailed wood rat can climb trees, and will occasionally locate its stick house up a tree, it is less arboreal than its semi-arboreal cousin, the dusky-footed wood rat.
Bushy-tailed wood rats are a solitary and territorial species – males spend considerable time marking their territory with their ventral musk glands, which they rub on toilet posts, food caches and nests. This can also create a very recognizable odour when found nesting inside your home.
Seasonal Activities and Movement Patterns
The bushy-tailed wood rat does not hibernate, instead it actively prepares for the winter by stockpiling a cache of vegetation, which it gathers and dries in the sun during the growing season. Winter months are primarily spent under the snow among the cover provided by their rocky habitat, however, short trips may be made over the snow’s surface.
Bushy-tailed wood rats do not travel significant distances throughout the year (with perhaps the exception of dispersing juveniles), remaining in the near vicinity of their stick houses and nesting sites.
Good indicators of the presence of a bushy-tailed wood rat are the deposits of urine and feces that accumulate within this animal’s home range. Feces and urine form a thick, tar-like substance often mistaken for some kind of mineral, if deposited in a spot sheltered from the rain. Bright white streaks result from urine deposited on rocks exposed to rain, the thinking is rain leaches out the organic components of the urine leaving a white calcareous deposit behind – a useful sign to look for when determining occupation (or former occupation) of an area by a wood rat. Because feces and urine deposits are quite perpetual, lasting for thousands of years in sheltered areas such as caves and decades on exposed surfaces, care must be taken not to confuse past use of a site with that of current use. Locating fresh streaks of urine can quickly differentiate that of an old site, the distinction being fresh urine’s transparent yellow to opaque brown colour, skunky odour and stickiness.