Breeding usually occurs in the spring. Woodrats produce 1 to 4 young per litter and may produce more than 1 litter per year in the southern parts of the US.
Woodrats climb readily and are usually active at night. Most species build a large stick den or house on the ground or in trees, but some species live in rocky outcroppings. These houses are typically occupied by one individual or by a female and her young. One animal may inhabit several houses. A nest, usually made of finely shredded plant material, is located within the larger house. Because they collect food and objects, particularly shiny ones, woodrats are also called pack rats. These collections on or near their dens are called middens.
Each species of woodrat is generally restricted to a given type of habitat within its range. Woodrats occur from low, hot, dry deserts to cold, rocky slopes above timberline. Table 1, below, tells the habitat preferences for each of the eight species.
The food habits of woodrats are relatively specific for the individual species (see Table 1). Species such as the bushytail woodrat, for example, feed primarily on green vegetation, twigs, and shoots, whereas the Mexican woodrat feeds on seeds, fruits, acorns, and cactus. Woodrats may also be attracted to human food supplies in buildings. When nesting inside buildings, woodrats usually continue to feed outside. Trails 3 to 4 inches wide from the building to the outside may be visible.