To city dwellers "rat" is apt to mean the house rat. Our smaller gentle native wood rat, or pack rat is only distantly related. He approaches our idea of a "nice" animal, with larger ears and eyes, a blunter nose, hairy tail, and softer fur, lighter in color below and on the feet. Three species live in West Texas, the whitethroated, the gray, and the Mexican.
The pack rat is nocturnal; he is rarely seen during the day, scurrying into his house. The rat is common enough to be an important item of diet for the Great Horned and Barn Owls. Coyotes often tear up their nests and eat not only the rat but its stored food. His dwellings can be conspicuous and abundant, in some cases only 15 feet apart.
The rat is a compulsive builder. His house is sometimes four feet high. A standard ingredient of a house in rangeland are cowchips, which are insulating, absorbent, readily available, and light enough to be easily transported. Occasionally an individual prefers horse dung. The second major ingredient is loose fragments of weathered mesquite up to two inches in diameter. Next in importance are twigs of mesquite six inches long and one to three eighths of an inch in diameter. With their stiff thorns they are designed to protect the home. Pieces of cholla, prickly pear, and tasajillo cactus, are also often used. Yucca leaves and weed stalks and roots can be found on many packrat houses.
The house is usually located at the base of a mesquite tree or in the base of a branched mesquite shrub. This might be selected for shade, but the house itself is sufficient to keep the ground cool beneath it. More likely the roots serve as an additional deterrent to predators seeking to dig out the rat, and the green bark of the branches provides a convenient source of food. A few houses are built in clumps of the spiny lote bush, and its twigs are severed and used in the house. Some of the bark may be chewed.
The pack rat is not without a sense of the aesthetic, although it cannot rely on finding a wide variety of decorative pieces. Large feathers, a few rabbit bones, and excreta of various kinds are other decorative items observed. Near owl nests a house might be covered with a number of pellets composed of the fur, skulls and bones of pack rats.
Well beaten paths, three inches wide radiate from each house. If the grass is sparse, the paths are not conspicuous, but where the growth is heavy it is neatly trimmed along the edges of the paths. Fecal pellets litter the paths near the house. The paths lead to holes in the ground under the house, where the nest is located. The pack rat bears litters of two or three after four weeks gestation.
Pack rats eat insects, berries, grass, leaves, succulent plants such as cactus, and nuts. Without examining the animal's stomach, one would be led to believe that in the winter they live on mesquite bark, for all young mesquites are girdled, stripped, and nibbled to a height of seven or eight feet. He must be an excellent climber to avoid the thorns and nip off the small ends of the branches. No water is available for most packrats, and they would not drink it anyway. Nor can they convert food to water chemically, as some desert rodents do. They rely on moisture in their food.
Nature Notes is sponsored by the Dixon Water Foundation and is produced by KRTS Marfa Public Radio in cooperation with the Sibley Nature Center in Midland, Texas. This episode was written by Burr Williams of the Sibley Nature Center.