The opossum probably is a newcomer to Colorado. Settlers on the Great Plains planted trees to shelter their farms from wind and to beautify their towns and that allowed habitat for opossums. The opossum is about the size of a house cat, with a total length up to two feet and weighing as much as seven and a half pounds. Its long, coarse fur is gray. Its ears are naked, and the tail is nearly so. The nose pad is pink; the big toe is clawless and works like a thumb. They are active at night and do not hibernate. An opossum will bite if annoyed but most often will "play possum" if frightened, sprawled out with eyes closed, tongue out and heart rate reduced to almost nothing – a most convincing performance. Opossums have a "thumb" on their hind feet that helps them climb. In other words, they have a toe that works in the opposite direction from the other toes. The "opposable toe" lets opossums grab things the way humans do with their hands. They are the only furbearer with an opposable toe.
Range: The species first appeared in the southeastern corner of the state in 1903; its present range is in the eastern two-fifths of the state.
Habitat: Control of floods and prairie fires allowed woodlands to grow along major rivers. These changes extended habitat for opossums westward from their range to the eastern and southeastern parts of Colorado. Opossums den in burrows made by other animals, or under rocks, brush, buildings or in hollow trees.
Diet: Opossums are omnivores, eating any organic matter but emphasizing insects, fruits, seeds and birds’ eggs during the growing season. They eat carrion and earthworms during winter.
Reproduction: Opossums are marsupials, like kangaroos and koalas, so the female has a pouch in which the young are carried. Breeding begins in January. Females have two litters of five to 15 honeybee-sized young each year, but there are only 13 nipples in the pouch, so the excess young die. The young remain in the pouch for 90 to 100 days and mature at eight months. Average life span for opossums is about 16 months and rarely exceeds two years. Many are killed on highways.
By David M. Armstrong
Department of Ecology & Evolutionary Biology
Environmental Studies Program, University Museum of Natural History
University of Colorado-Bouldermausmann@aol.com