Colorado’s vast and varied landscape, stretching from high alpine tundra to expansive eastern plains, creates distinct ecosystems that support a remarkable diversity of wildlife. This geographic range provides a haven for animals adapted to everything from arid grasslands to dense mountain forests. The state is recognized as a premier location for wildlife viewing, offering opportunities to observe species that are often elusive elsewhere.
Large Mammals of the Mountain and Forest Ecosystems
The high-country forests and alpine zones of Colorado are home to several large mammal species adapted to life at elevation. Rocky Mountain Elk, one of the state’s most iconic ungulates, undertake seasonal movements, migrating between high-altitude summer ranges and lower winter ranges. These movements are driven by the search for quality forage and milder weather. Adult males can weigh over 700 pounds and are recognizable by their massive, branching antlers.
Moose have successfully expanded their range across the mountainous regions following reintroduction efforts beginning in the late 1970s. They prefer riparian areas, feeding on willows and other aquatic vegetation. This habitat expansion has led to a thriving population, with the Shiras subspecies now found across the northern and western mountains.
Rocky Mountain Bighorn Sheep, the state’s official mammal, are adapted to steep, rocky terrain, frequently found above 7,000 feet. Their specialized hooves feature a hard outer rim for traction and a soft inner pad that grips rock ledges, making them agile climbers. Rams are distinguished by their massive, curled horns, which are used in head-butting contests during the rut.
The most common deer species in the mountains is the Mule Deer, named for its large ears. Unlike the White-tailed Deer, Mule Deer move with a stiff-legged, four-footed bounding gait called pronking. They inhabit a wide range of forested and brushy habitats, often moving to lower foothills during the winter months.
Colorado is home only to the American Black Bear, though their coloration frequently varies, appearing brown, cinnamon, or blonde. These omnivores gorge themselves during a fall period called hyperphagia to prepare for winter hibernation. During denning, the bear’s body temperature and metabolic rate drop significantly, allowing them to survive for months without eating or drinking.
Mountain Lions, also known as cougars or pumas, are the state’s largest native cats, found predominantly where their primary prey, deer and elk, are abundant. These powerful, solitary predators are elusive. They are mostly active from dusk till dawn, relying on stealth and ambush to hunt in the rugged terrain of the foothills and mountains.
Wildlife of the Eastern Plains and Grasslands
East of the Rocky Mountain foothills, the landscape transitions into the drier expanse of the Great Plains, supporting a distinct community of animals adapted to sparse cover and arid conditions. The American Bison, North America’s largest land mammal, once roamed these grasslands in the millions and now exists in managed conservation herds. As a keystone species, their grazing and wallowing behavior helps maintain the health and structure of the shortgrass prairie ecosystem.
Pronghorn, often mistakenly called antelope, are the fastest land mammals in North America, capable of reaching speeds up to 60 miles per hour. This speed, along with their exceptional eyesight, is an adaptation to surviving in the open, treeless environment. They can spot predators from great distances and sustain high speeds over long distances.
Prairie Dogs are a foundational species of the plains, living in large, interconnected burrow systems called “towns.” Their constant digging aerates the soil and creates microhabitats that benefit numerous other species. Their colonies are often shared with the small, diurnal Burrowing Owl, which nests and raises its young in abandoned prairie dog burrows.
The plains ecosystem also supports common predators like the Coyote and various species of foxes, including the Kit Fox. Coyotes have a diverse diet, consuming small mammals, insects, fruits, and carrion, allowing them to thrive in human-modified landscapes. These predators play an important role in regulating the populations of smaller plains animals.
Avian, Aquatic, and Herpetological Residents
The state’s diverse geography hosts a rich array of bird, fish, reptile, and amphibian species. Among the avian residents are iconic raptors. The Bald Eagle is often seen near open water sources, particularly during the winter months. The Golden Eagle prefers open country and mountainous terrain, hunting small to medium-sized mammals. The Peregrine Falcon, the fastest bird in the world, nests on high cliffs and can reach speeds over 200 miles per hour during its hunting stoop.
Colorado’s cold mountain streams and rivers are known for their trout populations, which are central to the state’s aquatic life. The Cutthroat Trout is the only trout species native to the state, with subspecies like the Greenback Cutthroat being a conservation focus. Non-native species such as Rainbow Trout and Brown Trout are also abundant, thriving in cold-water habitats throughout the Rockies.
Reptiles and amphibians are found mainly in the lower elevations and riparian zones. The Bullsnake, a powerful constrictor and the largest snake species in Colorado, is often mistaken for a rattlesnake due to its defensive behavior of coiling and shaking its tail. The Prairie Rattlesnake is the most common of the three venomous species found in the state, inhabiting the prairies and foothills below 9,000 feet.
Amphibians like the Barred Tiger Salamander, Colorado’s only native salamander, and various species of frogs and toads rely on moist or riparian habitats. To survive in arid environments, some toads, like the Woodhouse’s Toad, can remain dormant in underground burrows, emerging only during the rainy season to breed. These smaller residents are important indicators of environmental health.