Colorado's great range in elevation and temperature contributes to a variety of vegetation, distributed among five zones: plains, foothills, montane, subalpine, and alpine. The plains teem with grasses and as many as 500 types of wildflowers. Arid regions contain two dozen varieties of cacti. Foothills are matted with berry shrubs, lichens, lilies, and orchids, while fragile wild flowers, shrubs, and conifers thrive in the montane zone. Aspen and Engelmann spruce are found up to the timberline. As of 2003, 13 plant species were listed as threatened or endangered, including three species of cacti, two species of milk-vetch, Penland beardtongue, and Colorado butterfly plant.
Colorado has counted as many as 747 non-game wildlife species and 113 sport-game species. Principal big-game species are the elk, mountain lion, Rocky Mountain bighorn sheep (the state animal), antelope, black bear, and white-tailed and mule deers; the mountain goat and the moose—introduced in 1948 and 1975, respectively—are the only non-native big-game quarry. The lark bunting is the state bird; blue grouse and mourning doves are numerous, and 28 duck species have been sighted. Colorado has about 100 sport-fish species. Scores of lakes and rivers contain bullhead, kokanee salmon, and a diversity of trout. Rare Colorado fauna include the golden trout, white pelican, and wood frog. Nineteen animal species were listed as endangered or threatened by the US Fish and Wildlife Service in 2003. The Mexican spotted owl and bald eagle are among threatened species. The razorback sucker, gray wolf, whooping crane, black-footed ferret, southwestern willow flycatcher, and bonytail chub are among endangered species.