Wildlife viewers fascinated by reality shows like
Hoarders or
Hoarding: Buried Alive should get off the couch and go out looking for woodrats. These animals are famous for their compulsion to accumulate and store large quantities of nonessential things. Most people know woodrats by their aliases—pack rat or trade rat. "Pack rats" have a tendency to pack away any small objects they can carry. If these "trade rats" find something they want, they will drop what they are currently carrying, for example a can tab, and "trade" it for the new item. Shiny objects are particularly enticing, but anything, from stones and campground trash to eating utensils, could spark their interest.
Woodrats combine some of the items they accumulate with sticks, twigs, bone, cacti, manure, and bits of plant materials to construct large houses. Mostly, they place their houses above ground; beneath rock outcrops, in rock piles, under shrubs or cactus, or in caves. Occasionally, woodrats use the abandoned burrows of other animals or take up residence in parked or abandoned vehicles or human houses. The houses or "dens" provide protection from predators and extreme temperatures, and a place for food storage.
Woodrats place their other gathered treasures in their "midden", a fancy name for "garbage pile". Woodrats frequently urinate and defecate on their garbage piles to mark their territory. The urine is thick and viscous and when it crystallizes, it glues the entire garbage pile together. The urine, feces, and midden materials bind into a cement-like mass that mummifies the "junk", preserving it indefinitely. Good den or home sites are used by generation after generation of woodrats. Year after year, the waste pile grows and grows. Some middens have been found that date back nearly 50,000 years! Far from being a problem, these garbage collections function as biological time capsules, preserving fossil examples of representative plants, pollen, and even animal bones present in the environment over time. Woodrat middens provide scientists with a window into the past.
Woodrats are an ancient group of species and have existed since before the last ice age. There are presently 21 living species of woodrat, occurring in a very wide range of habitats, from the edge of the Arctic Circle all the way to the tropics of Nicaragua. They occur throughout western Canada, most of the U.S., Mexico and Central America. There are six species in Colorado.
Woodrats’ eyes are large, their protruding ears are nearly bald, and they usually have light-colored feet and bellies. The fur varies in color among species from gray to reddish-brown above and from white to rust-colored on the under-parts. Some populations of the desert woodrat and the white-throated woodrat are black. They vary in size from the foot-long desert woodrat to the more than 18-inch-long bushy-tailed woodrat. Woodrats climb readily and are usually active at night. The food habits of woodrats are relatively specific for the individual species. Species such as the bushy-tailed woodrat, for example, feed primarily on green vegetation, twigs, and shoots, whereas the Mexican woodrat feeds on seeds, fruits, acorns, and cactus.
Here’s where to look for each of Colorado’s woodrats or their houses and middens:
- White-throated woodrat: Found in pinion-juniper woodlands or juniper and shrub and prickly pear environments in southwestern Colorado or various habitats in the southeastern corner of the state.
- Bushy-tailed woodrat: A common woodrat, found in the montane and subalpine forests and alpine talus areas of the state.
- Eastern woodrat: On the eastern plains in rocky draws, riparian woodlands, and shrublands with yucca and cactus.
- Desert woodrat: In northwestern and west-central Colorado in canyon lands and semi-arid shrublands.
- Mexican woodrat: Found on rocky slopes and cliffs in montane shrublands, pinion-juniper woodlands, and montane forests.
- Southern plains woodrat: Found in the extreme southeastern corner of the state in grasslands with prickly-pear and candelabra cactus (cholla).