Do you want to learn about the mammals that live in Colorado?
Luckily, you’ve come to the right place!
I have compiled a list of the most common and interesting mammals in Colorado, with photos, facts, and RANGE MAPS. As you will see, there are lots of species, each with different and interesting habits and traits.
Here are 52 types of MAMMALS found in Colorado!
#1. American Black Bear
- Ursus americanus
- Adults range from 5 to 6 feet tall and weigh 200 to 600 pounds.
- Coloration ranges from mostly black on the east coast to brown, cinnamon, or blonde in the west, and blue-gray or even creamy white in some populations.
- They have a flat back, small head, rounded ears, and non-retractable claws.
American Black Bears occupy various habitats in Colorado but generally prefer inaccessible terrain.
Black bears are sometimes considered a nuisance because they sometimes damage cornfields, honeybee hives, and berry farms. In addition, they’re easily attracted to garbage, bird feeders, and coolers. Make sure to NEVER feed them, as this can make the bear not afraid of humans, which is dangerous for both people AND the bear.
Generally, Black Bears are timid around people. Unlike grizzly bears, females with cubs rarely attack people, often just sending their cubs up a tree so that they can retreat safely.
Black Bears are naturally active in the evening and early morning but sometimes alter their activity patterns for food availability. Bears may become active during the day when garbage and other human food sources are available. Black Bears in campgrounds often develop nocturnal activity patterns.
Despite the common belief, Black Bears in Colorado don’t truly hibernate.
Instead, they enter a state of shallow torpor. In this state, their body temperature decreases, their metabolism slows, and they don’t need to wake to eat, drink, urinate, or defecate. Consequently, Black Bears must put on a heavy layer of fat in the fall to survive through winter and spring.
#2. Bighorn Sheep
- Ovis canadensis
- Adults stand 30 to 41 inches tall at the shoulder and weigh between 160 and 315 pounds.
- Their coloring ranges from light to dark brown or grayish with white on the muzzle, rump, and belly.
- They have muscular bodies and wide-set eyes, and males have large curved horns that can reach over 3 feet and weigh over 30 pounds. Females have shorter horns with only a slight curvature.
Bighorn Sheep occupy cool mountainous regions, sometimes walking ledges only two inches in width. Their steep mountainous habitat helps protect them from predators. They move seasonally, concentrating in protected lowland valleys in the winter and spreading over upland areas in the summer.
Their diet also varies seasonally. In the warmer months, Bighorn Sheep feed primarily on grasses, sedges, and clovers, while in the winter, they eat more woody plants like willow and sage. They also visit natural salt licks to consume minerals.
Bighorns are ruminants, meaning that they have a complex four-part stomach that allows them to eat large portions quickly and then move to the safety of cliffs and ledges. There, they can rest and digest their food safe from predators. Bighorns also gain moisture from this process, allowing them to go for long periods without water.
These mating displays consist of males ramming at up to 40 miles per hour! You can hear the sharp crashing sound up to a mile away. Thankfully, Bighorn Sheep have thick and bony skulls, allowing them to absorb this shock with little damage.
- Cervus canadensis
- Adults stand 4.5 to 5 feet tall at the shoulder and weigh between 400 and 800 pounds.
- Their coloring is light brown with a dark brown shaggy mane from neck to chest in winter and reddish-brown in summer.
- They have thick bodies, short tails, and long legs, and bull (male) Elk grow massive antlers yearly.
The Elk is one of the largest mammals in Colorado.
They can be found in deciduous woodlands, boreal forests, mountainous areas, and grasslands. Most populations migrate seasonally. During the spring, they follow the retreating snow, traveling to higher elevations to graze. In the fall, they return to lower elevations and wooded areas that afford greater food availability.
Elk are herbivores that consume an average of 20 pounds of plant material per day! Elk are ruminants, meaning they have four-chambered stomachs. This trait allows them to eat quickly and then move to more sheltered areas to digest their food.
This species is one of the most gregarious members of the deer family and forms herds of up to 400 individuals. The herds are separated into small male groups and larger female groups. Female Elk sometimes produce an alarm bark to warn herd mates of danger. Conversely, males produce a high-pitched, bugling call during the rut to signal their availability and fitness to females.
#4. Mountain Goat
- Oreamnos americanus
- Females weigh 125 to 180 pounds.
- Males weigh between 135 and 300 pounds and have a more developed chest.
- They have white coats, split hooves, and shiny black horns.
Mountain Goats spend most of their time at high elevations above the tree line, often exceeding 13,000 feet above sea level. They move to lower elevations to access salt licks, seek cover, or find available forage. They are the least studied large mammal in Colorado due to their remote, high-altitude habitats.
These mammals are herbivores and spend most of their time grazing on grasses, mosses, lichens, twigs, and leaves. They are ruminants with four-chambered stomachs. This feature allows them to eat quickly and then regurgitate, re-chew, and slowly digest their food to break down tough plant matter.
One of my favorite things about Mountain Goats is the nicknames for males, females, and babies! Nannies (females) and billies (males) have extensive mating rituals that last weeks. Billies stare at nannies, paw “rutting pits,” and get into showy fights that sometimes result in injuries. After mating, the sexes separate for most of the year. The billies split off into smaller bachelor groups of just two or three individuals, while the nannies form large nursery groups, which include the babies, or “kids.”
#5. Mule Deer
- Odocoileus hemionus
- Adults are 4.5 to 7 feet in length and weigh between 130 and 280 pounds.
- Their coloring is tan to brown in summer and brownish-gray in winter, with a light gray face and distinctive black mask.
- They have large ears and white tails that are black at the tip, and males have branched antlers.
Mule Deer, named for their big, mule-like ears, are iconic mammals in Colorado. They’re found in rocky, arid environments and thrive in areas with a mix of early-stage plant growth and diverse shrubs.
This species feeds on trees and shrubs rather than grasses. Unlike cattle and Elk, which eat large quantities of plant materials with relatively low nutritional value, Mule Deer are selective. They prefer to feed only on high-quality young plants to thrive.
Mule Deer are social animals. Females tend to stay in multi-generational family groups. Bucks leave the family group after a year and are solitary or travel in small groups with other bucks. Family groups sometimes join to form a larger herd for greater protection in the winter.
- Antilocapra americana
- Adults are 4.5 feet in length and weigh between 90 and 150 pounds.
- Their coloring is reddish-brown to tan with white stripes and markings on their necks, faces, stomach, and rump.
- They have long legs, short tails, long snouts, large eyes, and a pair of horns 10 to 12 inches long in males.
The Pronghorn is the fastest land mammal in Colorado!
They can run at speeds up to 60 miles per hour. They’re the second fastest land mammal worldwide, behind Cheetahs. And while Cheetahs would win a sprint, Pronghorns can maintain their speed for long distances.
Look for this species in open plains, fields, and deserts. These amazing animals seldom need to drink water, instead gaining almost all the moisture they need from the grasses and plant matter they eat.
Pronghorn have large eyes and excellent vision, which allow them to see predators at a distance. They also communicate visually. If one Pronghorn spots a predator, it will raise the white hairs on its rump, making the white spot appear much larger. Other Pronghorn will see this and know to be on high alert.
#7. White-Tailed Deer
- Odocoileus virginianus
- Adults range from 63 to 87 inches long and stand between 31 and 39 inches tall at the shoulder.
- Their coloring is tan or brown during the summer and grayish in winter, with white on the throat, chest, and underside of the tail.
- The males have antlers which they shed in the winter.
The White-tailed Deer is the most numerous large mammal in Colorado!
White-tailed deer have an extensive range in North America and are able to thrive in various habitats, including coniferous, mixed, and deciduous forests, sawgrass and hammock swamps, cactus and thorn brush deserts, brushy areas, and farmlands. You’re most likely to see White-tailed Deer around dawn and dusk when they forage.
They are also completely comfortable in suburban environments, and it’s common for them to live in small wooded parks near housing developments. The herd in my neighborhood is particularly fond of our bird feeders. They stop by for a snack almost every evening!
There aren’t many things cuter than a baby deer! The fawns are born with white spots and are able to walk almost right away. The does may leave the fawns to forage for hours at a time. While their mother is away, the fawns lay flat on the ground with their necks outstretched and are well camouflaged. The female deer always come back to the baby, so make sure not to disturb the fawn if you find one!
#8. American Bison
- Bison bison
- Adults stand up to 6 feet tall, and males can weigh more than 1 ton while females reach 900 pounds.
- They have long, deep brown fur, cloven hooves, and a noticeable hump over their shoulders.
- Both males and females have short, curved, hollow horns that can grow up to 2 feet.
While you may have heard them called buffalo, the correct name for this species is American Bison. Buffalo are native to Africa and Asia, while Bison, a distantly related animal, is native to North America.
Bison are well adapted to the changing seasons across their range. They’re constantly on the move, walking even while eating. To forage during the winter, they use their large heads to sweep aside the snow. During summer, Bison often wallow, rolling on the ground and creating shallow depressions in the soil. Wallowing helps them to cool off and soothe insect bites.
American Bison were once the most widespread herbivore on the continent, with a population of at least 30 million.
Sadly, by 1900 as few as 1,000 bison remained. While some Bison were hunted for food, most were killed for sport and to drive out Native American groups that relied on Bison as settlers expanded westward. Finally, in the 1900s, they received federal wildlife protection and were brought back from the brink of extinction. Today, approximately 31,000 wild bison are found on federally protected lands and reserves.
#9. Canada Lynx
- Lynx canadensis
- Adults measure 19 to 22 inches tall at the shoulder and weigh between 11 and 37 pounds.
- Their coloring is grayish-brown mixed with buff or pale-brown fur on the back and grayish-white or buff-white fur on the belly, legs, and feet.
- They have long legs, wide, flat paws, long black tufts on triangular ears, and a short black-tipped tail.
Canada Lynx live in cold, moist, boreal forests with snowy winters. The Lynx’s long legs and large paws allow it to hunt and travel in deep snow. This species is exclusively found in areas also occupied by its favorite prey, the Snowshoe Hare.
Lynx are primarily nocturnal and can spot prey up to 250 feet away in the dark. As a result, they are incredibly elusive and rarely seen by humans. A single Canada Lynx may cover more than five miles per day searching for food. They’re excellent swimmers and are adept at climbing trees to escape predators.
Canada Lynx have an interesting, often studied predator-prey relationship with snowshoe hares. The two species are so linked that their populations fluctuate in sync with one another. Adults may survive periods of hare scarcity by hunting other prey. However, Lynx kittens often don’t fare as well during these periods, which leads to a population decrease. When Lynx populations go down, the populations of snowshoe hares rebound, and the cycle starts over again.
- Lynx rufus
- Adults weigh 15 to 35 pounds, stand 18 to 24 inches tall, and measure 28 to 47 inches in length.
- Their coloring is buff to brown, sometimes with a reddish tint, and black and brown spots and stripes.
- They have facial ruffs, ear tufts, white spots, and short, bobbed tails.
Bobcats are solitary, elusive, and shy mammals that are rarely seen in Colorado.
These cats are highly adaptable and found in various habitats. They may be seen in residential areas. However, they generally avoid extensively cleared agricultural lands.
As carnivores, Bobcats are highly skilled hunters. They can climb, run up to 30 miles per hour, and leap high enough to grab low-flying birds. They patiently stalk their prey until they are close enough to pounce.
The largest threat to Bobcat populations is habitat fragmentation due to their large home ranges and elusive nature. However, rodenticides can also cause issues in populations when they feed on contaminated prey.
- Puma concolor
- Adults stand 24 to 35 inches tall at the shoulder and weigh between 64 and 220 pounds.
- Coloration ranges from reddish-brown to tawny or gray, with a black tip on their tail.
- They have round heads, pointed ears, and powerful forequarters.
Their large hind legs and massive paws help give Cougars incredible athletic ability. They can jump 15 feet high and 40 feet in distance and sprint at 50 miles per hour. Yet, despite their impressive speed, they generally wait and ambush prey.
Except for females raising young, adult Cougars generally only kill one large animal every couple weeks. Then, they drag the kill to a preferred area and cover it with brush, returning to feed off it over a few days.
While cougars don’t have predators besides humans, they may get into territory conflicts with other large predators. Cougars dominate one-on-one confrontations with wolves but are weaker when confronting packs. Generally, brown and black bears can drive off cougars with little effort.
Cougars have the most amount of names of any mammal found in Colorado.
While Cougar seems to be the most common, these large cats are also known as catamount, mountain lion, puma, ghost cat, and panther.
#12. Red Fox
- Vulpes vulpes
- Adults range from 18 to 35 inches in length and weigh 7 to 31 pounds.
- Their coloring ranges from pale orange or red to deep reddish-brown on their upper parts with white on their underside.
- They have black feet, a fluffy white-tipped tail, and large, pointy, black-tipped ears.
Red Foxes are arguably the most beautiful mammal in Colorado!
These canines are often thought of as cunning and smart, with good reason! They’re excellent hunters and foragers. They also cache food and are adept at relocating it. Although they prefer rabbits, fish, and berries, they won’t hesitate to eat anything readily available.
This species has a distinctive way of hunting mice and other small rodents. Once the prey has been detected, they stand motionless, waiting and listening. Then they leap high into the air and bring their forelegs straight down, pinning the rodent.
Once baby foxes, known as kits, reach adulthood, their biggest threat is humans, who hunt and trap them for fur or kill them to protect livestock, such as chickens. Red Foxes can live 10 to 12 years in captivity but average only about three years in the wild.
#13. Gray Fox
- Urocyon cinereoargenteus
- Adults range from 31.5 to 44.3 inches long and stand 12 to 16 inches tall.
- Their fur is peppery gray on top and reddish brown everywhere else.
- They have a pointed muzzle and ears, long hooked claws, and a bushy tail with a black stripe on top.
Gray Foxes live in deciduous forests in Colorado with a mix of brushy and woodland areas. They occasionally visit agricultural lands, but not as frequently as Red Foxes. Gray Foxes also prefer habitats with access to water, so you’re more likely to see them near rivers or lakes.
You’ll have a tough time finding this species, since they are primarily nocturnal and incredibly skittish of people. During the winter breeding season from December through March, they socialize with their mates but spend little time with other foxes.
Females give birth to litters of one to seven pups in the den, and the fathers provide most of their food after they are weaned. Males teach their pups hunting skills by practicing pouncing and stalking, and they begin to hunt at around four months of age.
#14. Kit Fox
- Vulpes macrotis
- Adults range from 18 to 21 inches in length.
- Their coloring is yellowish to gray with a dark-colored back, light-colored undersides, and distinct dark patches on each side of the nose and at the end of the tail.
- They have exceptionally large ears placed close together on their head.
Despite their delicate appearance, Kit Foxes thrive in some of the harshest climates in Colorado. They typically occupy arid desert scrub, chaparral, and grassland habitats, but also occasionally use agricultural areas and urban environments.
Although they can dig their own dens, Kit Foxes frequently take over burrows from prairie dogs, American Badgers, and other rodents. They use dens year-round and have several in their territory, which they rotate using. They spend most of the day in their dens, only coming out to hunt at night.
Kit foxes are believed to live an average of 5.5 years in the wild, but researchers have found widely varied results from 3 to 4 years to 7 to 12. Kit foxes are often preyed on by coyotes but may also be eaten by bobcats, wolves, raptors, feral dogs, red foxes, and American badgers. They’re also often hit by cars and are sometimes illegally hunted and trapped for their fur.
#15. Swift Fox
- Vulpes velox
- Adults are about 31.5 inches long, and males are slightly larger than females.
- Their fur is light gray with orange-tan coloring on the sides and legs.
- They have black patches on either side of the snout, and the tail is bushy and black-tipped.
Look for Swift Foxes in prairie and desert habitats in Colorado, where they build dens in sandy soil in open prairies, plowed fields, or along fences. During the summer, they’re nocturnal and spend their days in their dens. In the winter, they often come out during the day to sunbathe for short periods. Spending time in their dens also helps them avoid predators, which include Red Foxes and Coyotes.
As their name suggests, these animals are quick! Swift Foxes can reach speeds of 31 miles per hour. Their speed helps them avoid predators and catch prey, which includes insects, small mammals, fish, reptiles, and occasionally birds.
Swift Foxes were once abundant across the great plains, but became severely endangered in the 1930s. They disappeared from about 60% of their former range. However, Swift Fox populations have rebounded thanks to successful reintroduction efforts, particularly by the Canadian government and several Native American tribes within Colorado.
- Canis latrans
- Adults range in length from 3 to 4.5 feet and weigh between 15 and 44 pounds.
- Their coloring is grayish to yellow-brown on top with white underparts.
- They have a bushy tail, large, triangular ears, narrow muzzle, black nose, and yellow eyes.
Coyotes have a large range in North America and are found in various habitats, from the tropics to the tundra. Coyotes expanded their range after the near extermination of wolves and cougars by European settlers.
As with habitat, coyotes are highly versatile in their food selection. Despite being primarily carnivorous, they consume various plants, including berries, grass, and food crops. They will eat almost anything, and this extensive menu allows them to thrive in nearly every environment in Colorado!
Even if you haven’t seen one, you’ve probably heard a Coyote before! They’re extremely vocal and communicate through howls, yips, whines, and barks. These vocalizations are used to warn pack mates of danger, greet each other, and play.
Sadly, Coyotes are commonly hunted and trapped for fur and sport.
#17. Black-Tailed Jackrabbit
- Lepus californicus
- Adults are 18.5 to 24.8 inches long and weigh between 2.86 and 6.83 pounds.
- Their fur is dark buff peppered with black, with black ear tips, a stripe down the center of the back, and a black rump and tail.
- They have a lanky, lean body, long legs, and long ears.
Unlike many prey animals, which prefer dense cover, Black-tailed Jackrabbits use open habitats to spot predators first. Their large eyes are placed high on the sides of their slightly flattened heads, allowing them a nearly 360-degree range of vision.
Black-tailed Jackrabbits are nocturnal and inactive during the hot hours of the day and rest under bushes. Their large ears help them to expel heat in their arid, hot climate. This species relies on camouflage and speed for defense from predators. They can clear 20 feet in a single bound and reach speeds of 30 to 35 miles per hour.
Jackrabbits are sometimes considered a pest species because they can do incredible damage to croplands, orchards, and pastures. Their populations tend to fluctuate drastically, peaking every 6 to 10 years. These fluctuations are partly caused by a disease called tularemia which has at times killed more than 90% of the western population.
#18. White-Tailed Jackrabbit
- Lepus townsendii
- Adults weigh between 6.6 and 8.8 pounds.
- Their color ranges from yellowish-gray to brown on the upper parts, with white or gray on the underside.
- Year-round, they have a white tail and exceptionally long, black-tipped ears.
White-tailed Jackrabbits are predominantly found in plains, prairies, and grasslands. However, they can be hard to spot because they’re well camouflaged and incredibly agile. They can leap 10 feet and run up to 40 miles per hour!
These hares are no stranger to agricultural areas and take advantage of farms for food and shelter. They’re known to feed on alfalfa, winter wheat, and western wheatgrass. White-tailed Jackrabbits will even winter in barns, feeding on the hay inside.
Unfortunately, local populations have dramatically declined in areas with modernized agricultural operations. As a result, jackrabbits have lost habitat and food sources in these areas and face grazing competition from livestock.
#19. Snow Shoe Hare
- Lepus americanus
- Adults range from 16.4 to 20.4 inches in length.
- In summer, the fur is a rusty grayish brown with a dark line down the middle of the back.
- In winter, the fur is almost entirely white except for black eyelids and blackened tips of the ears.
Snowshoe Hares are perfectly adapted to cold, snowy areas of boreal and coniferous forests. They get their name from the thick fur and large toes on their back feet, which allow them to run across the snow without sinking in. In warmer climates, Snowshoe Hares are found only in the mountains where the weather is cooler and snowy.
You’re most likely to spot this mammal in Colorado at dawn or after dusk. Snowshoe Hares are primarily herbivorous and consume various plants depending on the season. In summer, they feed on grasses and wildflowers. Then, they switch to buds, twigs, and bark from conifer trees in winter.
About 85% of leverets (baby hares) won’t make it through their first year of life. Those that do survive live up to five years in the wild. They have many predators, including squirrels who eat the young, Lynx, bobcats, mink, wolves, coyotes, and foxes. Unlike rabbits that freeze when threatened, Snowshoe Hares often rely on their speed to escape to cover.
Snowshoe Hare populations are believed to be currently stable. However, researchers believe they face a unique threat from climate change. Regardless if there is snow or not, they continue to turn white in the winter, putting them at an increased risk for predation if they are not blending into their surroundings.
#20. Desert Cottontail
- Sylvilagus audubonii
- Adults are 14 to 15 inches long and weigh between 1 and 2 pounds.
- Their coloring is gray-brown above and lighter on the undersides with an orange throat patch and a fluffy white tail.
- They have large feet, round eyes, puffy round tails, and long, wide, mostly furless ears.
The Desert Cottontail prefers drier habitats than most other cottontail species. They can be found in woodlands, grasslands, creosote bush, and deserts, especially rivers and streambeds.
These rabbits use thickets, brush, and grass to shelter from the day’s heat, creating shallow depressions to lay in. Occasionally, they will also use the burrows of other animals.
This species is most active in the evening and early morning. They forage on grass, twigs, and other plants. Desert Cottontails’ teeth grow continuously and are worn down by their rough diet. Though they aren’t social animals, females occasionally feed near each other without aggression.
Many animals, including coyotes, bobcats, and foxes, are predators of Desert Cottontails, but that doesn’t mean they’re easy prey. They can swim and run in zig-zag patterns at speeds up to 20 miles per hour to escape predators. They also climb trees and brush piles to avoid danger.
#21. Eastern Cottontail
- Sylvilagus floridanus
- Adults are about 16.5 inches long and weigh up to 3 pounds.
- Their coloring is reddish-brown on the upper body with white on the underparts and tail.
- They have distinctive, large eyes and a round, fluffy tail.
These small mammals are vulnerable to many predators in Colorado, so they require a habitat with good cover. Areas with a mix of grasses, dense shrub thickets, blackberry bushes, and brush piles are ideal. Well-drained fields with dense grass cover are often used for nesting.
One of their favorite places to nest is suburban yards! So, if you notice Eastern Cottontails hanging around your property, be careful when you mow your lawn. Although rabbit nests are usually slightly below ground level, lawn equipment is still dangerous for baby rabbits and mothers.
Eastern Cottontails consume a wide range of plant materials. They can be a nuisance for gardeners by eating garden plants and flowers. However, in winter, they eat woody materials from birch, oak, dogwood, sumac, and maple trees.
If threatened, Eastern Cottontails either freeze or flush. When they flush, they will run to cover in a zig-zag pattern reaching speeds up to 18 miles per hour. If grabbed, they may give a loud distress cry to startle a predator into releasing them.
#22. Mountain Cottontail
- Sylvilagus nuttallii
- Adults range from 13.8 to 15.4 inches long and weigh between 1.5 and 2.6 pounds.
- Their coloring is grayish-brown on top and white on the underparts, with long, dense, reddish-brown hairs on the hind legs.
- They have white whiskers and short, rounded ears with black tips.
Mountain Cottontails are predominately found in wooded or brushy areas. They’re crepuscular, so your best chance to see them is at dawn and dusk.
They feed near water and prefer grasses over other food sources. When these are scarce, they feed on sagebrush, western juniper, and juniper berries. Their habitats are generally sparse, so they move a lot, looking for areas with good food sources.
This species has many predators, including coyotes, bobcats, martens, hawks, eagles, owls, and rattlesnakes. When frightened, Mountain Cottontails may run several meters and then freeze or run in a semi-circular path to confuse predators or find cover. In addition, they often hide in burrows made by other animals.
#23. Striped Skunk
- Mephitis mephitis
- Adults range from 18 to 32 inches long.
- Their coloring is black with two thick white stripes running down the back and tail and a thin white stripe from snout to forehead.
- They have a bushy black tail, small triangular heads, short ears, and black eyes.
Striped Skunks have perhaps the worst reputation of any mammal in Colorado.
They’re best known for their unusual defense system. When threatened, a Striped Skunk will first stomp its feet or handstand as a warning. If these aren’t heeded, the skunk bends its hindquarters to face the animal and releases its defensive smelly spray. The unpleasant, oily liquid can reach up to 20 feet and may cause nausea, intense pain, and temporary blindness.
Despite their foul odor, Striped Skunks provide benefits to humans in the form of pest control. In the summer, they’re largely insectivorous and feed heavily on grasshoppers, crickets, beetles, and bees. The best thing to do if you see a skunk is to give it space. They usually move on quickly when they notice humans!
Striped Skunks have stable and abundant populations. However, some local populations have been affected by rabies outbreaks. In addition, Striped Skunks face threats from severe weather, chemical exposure, and vehicle collisions.
These small mammals are typically very common in suburban areas but are rarely seen because they are nocturnal. As seen below, they often visit bird feeders to eat leftover seeds on the ground!
#24. Western Spotted Skunk
- Spilogale gracilis
- Adults measure 14.2 to 16.7 inches in total length.
- Their fur is glossy black with white spots.
- They are small and slender and have a fluffy black tail with a white tip and underside.
Western Spotted Skunks are much less common than their close relatives, the Striped Skunk. They prefer areas that provide extensive cover, and they’re rarely seen in open fields or yards.
This nocturnal omnivore primarily feeds on small mammals and insects such as carrion, reptiles, amphibians, bird eggs, small rodents, grasshoppers, scorpions, and arthropods. Occasionally, they will consume berries, fruit, and roots. They are both agile climbers and diggers.
Like Striped Skunks, this species sprays a noxious oily secretion if threatened. The smelly, toxic substance can temporarily blind an attacker.
Despite their excellent defense and hiding skills, their populations are decreasing, and some individual states have listed them as a species of greatest conservation need. They are most threatened by vehicle collisions, trapping, and pest control efforts.
#24. Eastern Spotted Skunk
- Spilogale putorius
- Adults are 14 to 24 inches long.
- They have long, soft, glossy, black fur with white spots and stripes on the ears and back.
- They have a small head, short legs, and a prominent, black, long-haired tail.
Eastern Spotted Skunks are found in various open habitats, including mature forests that provide adequate cover. They may also occupy agricultural areas and use buildings, corn cribs, rock piles, haystacks, and other debris for cover and den sites.
Although their preferred food during summer is insects, Eastern Spotted Skunks are omnivores. During the fall and winter, they feed on equal amounts of plant and animal matter. They consume bees and wasps, larvae, and honey. They will also eat other insects, eggs, and small animals.
When threatened, Eastern Spotted Skunks will often assume a defensive posture in which they do a handstand on their front legs with their tail straight up and back legs spread apart in the air. They can balance and move forward in this stance while aiming specialized glands at the predator. If this display doesn’t work, then they spray a smelly deterrent.
The population of these small mammals is believed to have declined by more than 90% in Colorado since the 1940s. As a result, they are listed as vulnerable on the IUCN Red List of Endangered Species. Contributing factors include unregulated over-hunting and trapping, habitat loss and fragmentation, widespread pesticide use, increased pressure from predators, and disease.
#26. American Hog-nosed Skunk
- Conepatus leuconotus
- Adults may grow up to 2.7 feet in length.
- They are black with a broad white stripe running from their head to their all-white tail.
- They have large, naked snouts, small eyes and noses, stocky legs, and 5-toed feet.
American Hog-nosed Skunks are most common in rocky terrain and mountainous areas. These habitats provide crevices and caves for denning, but they will also use hollow trees, old burrows, and underneath buildings.
This species is omnivorous, but most of its diet is made up of insects. They forage at night using their acute sense of smell to locate a meal. Their snouts and sharp front claws easily turn over topsoil, rocks, and other debris to search for food. This habit of rooting for food has earned them the nickname “rooter skunks” in some areas.
If threatened, American Hog-nosed Skunks typically flee with their tail curled over their back, looking for safety in their den, dense brush, or a hollow tree. However, they may turn and face a threat when cornered, stamping their feet while growling. If approached, they stand up on their hind legs, stomp down hard, and hiss. Finally, if they continue to be disturbed, they turn, raise their tail, and spray their pursuer with a noxious liquid.
- Procyon lotor
- Adults are about 3 feet long and weigh between 15 and 40 pounds, though some males grow to over 60 pounds.
- Their fur is grayish-brown with 4 to 6 black rings on the tail and a black “mask” marking around the eyes.
- They have bushy tails and paws with five long, finger-like toes.
These mammals are one of the most common in Colorado!
Due to their ability to adapt to humans, Raccoons have an extensive range and are found in forests, wetlands, suburbs, parks, and cities. They generally avoid large open areas and thrive in areas with water sources, abundant food, and den sites. They make dens in rock crevices, hollow trees or logs, burrows, caves, mines, old buildings, rain sewers, or other cavities for winter shelter and birth.
As opportunistic omnivores, Raccoons will eat both plant material and animals. They feed on practically anything they can fit in their mouths. Interestingly, in areas where food is abundant individual raccoons have been known to develop specific food preferences. Raccoons in urban locations are often larger than those in unpopulated areas because they have adapted to live on human hand-outs, pet food, and trash. They also generally have the benefit of fewer predators.
The second part of the Raccoon’s Latin name, “lotor,” translates to “washer,” referring to a unique behavior they exhibit. They often pick up food items and rub them with their paws, sometimes removing unwanted parts. This gives the appearance that they’re washing their food.
Lastly, they have REALLY cute babies. 🙂
- Bassariscus astutus
- Adults measure 12 to 16.5 inches long with 12 to 17-inch long tails.
- Their coloring is pale tan with a dark brown wash on the upper parts and pale buff on the underside.
- They have a bushy tail with black and white rings, large oval ears, a cat-like body, and a fox-like face.
Ringtails are one of the most unique-looking mammals in Colorado!
They’re sometimes called ring-tailed or miner’s cats, but despite these nicknames, they’re members of the raccoon family. Look for Ringtails in semi-arid climates of deserts, woodlands, and conifer forests. They’re also often found foraging in areas with trees near streams and rivers.
These nocturnal mammals spend their nights hunting and foraging. They are omnivorous, but the bulk of their diet is rodents, birds, reptiles, amphibians, insects, and carrion. They sometimes eat berries, acorns, and other fruits.
When threatened, Ringtails bristle and arch their tails over their heads to appear larger. If grabbed, they release a pungent, foul-smelling secretion and make a high-pitched screaming sound.
One of the biggest threats faced by ringtails is vehicle collisions. In addition, they often occupy habitats fragmented by roads and are nocturnal, making them especially susceptible.
#29. Yellow-bellied Marmot
- Marmota flaviventris
- Adults range from 18.5 to 27.6 inches long.
- Their coloring is yellow-brown to tawny above with a yellow or orange-russet belly.
- They have robust bodies with short, broad heads and small, furry ears.
Yellow-bellied Marmots occupy open, dry habitats, including woodlands, forest openings, and the alpine zone. They build burrows into rocky outcrops in meadows or grassy slopes. This species spends up to 80% of its life in burrows! In many areas, they hibernate from September to May.
Some Yellow-bellied Marmots are solitary, but others live in small groups or colonies. They have been observed grooming, playing, greeting, fighting, and engaging in dominance displays within their social groups.
Although Yellow-bellied marmots are affected by hunting, habitat degradation, and climate change, their population is stable. They’re found in many national and state parks, where they are protected from human disturbance.
#30. River Otter
- Lontra canadensis
- Adults grow 3 to 4 feet in length, including their tails.
- Their thick, protective fur is dark brown on the body and lighter brown on the belly and face.
- They have short legs with webbed feet, a long narrow body, and a long, muscular tail.
North American River Otters are semi-aquatic mammals that have an extensive range. They’re found in lakes, rivers, marshes, and estuaries in cold and warm climates. River Otters create dens along the shore that have entrances underwater. They forage at night but can be seen at all times of the day.
River Otters are lively, playful animals and are sometimes even spotted sliding around in the mud or snow. These activities help them to form social bonds and practice hunting techniques.
They use their long whiskers to detect prey in dark water, often grabbing a meal before the victim knows what’s happening. River otters are excellent swimmers, divers, and quick runners. They can stay underwater for up to eight minutes and run 18 miles per hour.
During the 19th and 20th centuries, river otters were heavily trapped and hunted for their fur to near extinction. Conservation and reintroduction efforts are helping many populations to recover; however, some northern populations are still considered vulnerable or imperiled. River Otters continue to face threats from water pollution and habitat destruction.
#31. Common Muskrat
- Ondatra zibethicus
- Adults range from 16 to 25 inches in total length and weigh 1.5 to 4 pounds.
- Their coloring is blackish-brown on the back, lighter brown with a reddish tinge on the sides, and pale on the underside.
- They have short front legs with small feet, strong hind legs with large, partially-webbed feet, and a vertically flattened, scaly tail.
Muskrats are one of just a few semi-aquatic mammals in Colorado.
They occupy marshes, streams, ponds, rivers, and lakes with fresh and brackish water. This species lives in dens built into riverbanks or lodges they construct from sticks. Muskrats construct homes with underwater tunnels and dry, above-water chambers. Interestingly, they will sometimes move into occupied beaver lodges and cohabitate with them.
Being mostly omnivores, Muskrats typically feed on aquatic plants such as cattails, water lilies, and duckweeds. But when food is scarce, they sometimes eat other animals, including crayfish, snails, frogs, insects, and fish.
Muskrats are an important part of the ecosystem in Colorado, helping keep areas of marshes open and creating essential habitats for waterfowl. Unfortunately, this species was introduced to Europe as fur stock and has become invasive in many countries. They cause issues by burrowing into dikes and levees and causing flooding.
#32. American Red Squirrel
- Tamiasciurus hudsonicus
- Adults are 11- 14 inches (28 – 35.5 cm) long.
- Their coloring is reddish-brown with a white belly.
- These tiny squirrels have inquisitive-looking faces with bright white rings around their eyes.
The American Red Squirrel is easy to identify compared to other squirrel species. As the name suggests, they have a reddish color and white belly that makes them easy to distinguish. Size-wise, they are both MUCH smaller than both gray and fox squirrels but larger than chipmunks.
American Red Squirrel Range Map
These small mammals are primarily found in Colorado in coniferous forests due to their diet, which consists of seeds from evergreen trees. But they are equally at home in deciduous forests, backyards, parks, and urban areas, where they adjust their diet to eat foods such as berries, bird eggs, acorns, hazelnuts, mushrooms, mice, and sunflower seeds from backyard bird feeding stations. American Red Squirrels even have a sweet tooth and are known to tap maple trees so they can eat the sugar from the sap!
These squirrels are BEST known for their aggressive personality!
Press PLAY to hear the sounds of an American Red Squirrel!
When I go hiking, I almost always see at least one American Red Squirrel, as they are not shy creatures. As soon as I’m spotted, the squirrel typically runs up a tree to sit and starts making loud chattering noises to alert the whole forest to my presence!
#33. Fox Squirrel
- Sciurus niger
- Adults are 17.7 – 27.6 inches (45 – 70 cm) long.
- They have gray-brown fur on the back and orange bellies.
- This species has bushy tails, rounded ears, and large black eyes.
Fox Squirrels are the largest tree squirrel in Colorado.
These small mammals can adapt to many different habitats in eastern Colorado. However, they are most often found in small patches of deciduous forests that include trees that produce their favorite foods, which are acorns, walnuts, pecans, and hickory nuts. To prepare for winter, they hide caches of these nuts all over the place to be eaten later when the weather turns cold.
In addition, Fox Squirrels thrive living around people. Consequently, they are commonly found in urban parks and neighborhoods.
Fox Squirrel Range Map
You will likely see Fox Squirrels foraging on the ground, as they spend much of their time there. But don’t let this fact fool you since they are still skilled climbers. In addition to scaling trees, they will easily climb a bird feeder pole to access birdseed. 🙂
#34. Least Chipmunk
- Tamias minimus
- Adults range from 7.3 to 8.7 inches long, including their tails, and weigh between 1.5 and 1.9 ounces.
- Their upper parts are orangish-brown with dark and light stripes down their back and sides, and their underparts are grayish-white.
- They have dark and light stripes on their face, a long bushy tail, and pouched cheeks.
As their name suggests, Least Chipmunks are the smallest of all chipmunk species! These little mammals can be found in boreal and temperate forests in Colorado.
Least Chipmunks are omnivores that are only active during the day. Interestingly, this species forages in a specific area until the food is depleted, then they mark that area with urine and avoid it until more food is available.
Least Chipmunks construct burrows for sleeping, nesting, caching food, and protection from predators. They also spend winters in these burrows. Least Chipmunks don’t truly hibernate, but they enter a torpor state in their burrow during the winter, waking only occasionally to eat.
#35. 13-Lined Ground Squirrel
- Ictidomys tridecemlineatus
- Adults range from 6.7 to 12.2 inches long.
- Their coloring is buff, golden, or yellow. The 13 lines of its name are alternating dark stripes and light yellow or white dotted lines.
- They’re small and slender, with small ears and a thin, sparingly bushy tail.
13-Lined Ground Squirrels prefer prairie habitats, however, they have adapted well to human presence. For example, they can be found in cemeteries, golf courses, parks, roadsides, and well-grazed pastures.
Look for 13-Lined Ground Squirrels around midday on warm summer days, which is when they are most active. This species doesn’t tolerate cold well and enter hibernation earlier than many other species. Interestingly, their heart rate drops from around 200 beats per minute to as low as 20, and their temperature falls to near freezing. During hibernation, they may lose up to 1/3 of their body weight.
Although they were historically only found in states with naturally occurring prairies, these squirrels have expanded their range eastward and northward into human-created clearings and development areas.
#36. Black-Tailed Prairie Dog
- Cynomys ludovicianus
- Adults are about 16 inches tall.
- Their coloring is tan with a light-colored belly and black-tipped tail.
- They have short ears and large black eyes.
Black-tailed Prairie Dogs prefer fine or medium-textured soils, which are ideal for building their complex underground burrows. Nesting chambers are near the bottom of burrows and have dry grass bedding. Listening chambers near the entrance of each burrow allow the prairie dogs to detect predators before leaving the safety of the burrow.
Prairie Dogs build their burrows close together to form colonies called towns. Towns are divided further into family neighborhoods called coteries. Within coteries, individuals perform specific tasks, including foraging, socializing with others, maintaining the burrow, and scouting for predators. A prairie dog standing look-out will alert others to danger with a series of bark-like whistles before retreating into a burrow.
The conservation of Black-tailed Prairie Dogs is essential because they’re keystone species, meaning other plant and animal species depend on them for survival. For example, Prairie Dogs help aerate and fertilize the soil and are an important food source for Burrowing Owls, Ferruginous Hawks, Swift Foxes, and endangered Black-footed Ferrets, whose decline can be linked to that of Prairie Dogs.
#37. Brown Rat
- Rattus norvegicus
Look for Brown Rats anywhere people are living, particularly in urban environments. They’re best known for living in sewer tunnels and subway systems, scavenging food from the trash.
Believe it or not, this small mammal isn’t native to Colorado. It’s thought to have originated in China and Mongolia.
Although many people find rats off-putting, others keep a sub-species of Brown Rats as pets. This subspecies, called the Fancy Rat, was bred specifically for the pet trade. Besides companion animals, rats can be trained for many jobs to assist humans, like detecting gunpowder for forensic teams and providing therapy support.
It’s a misconception that Brown Rats spread bubonic plague. In actuality, it’s more commonly spread through ground squirrels! Regardless, they can transmit infections of many kinds, as their blood can carry several diseases.
#38. Black Rat
- Rattus rattus
Interestingly, this small mammal is not native to Colorado.
Instead, it’s thought that the Black Rat came from India and was transported to North America on cargo ships. It’s now so widespread that it’s no longer considered a foreign species.
It’s considered a pest in the agricultural market because it feeds on various crops. Like other rodents, Black Rats can carry pathogens in their bodies. While they may not appear sick, they can spread infections like toxoplasmosis, typhus, and bubonic plague.
In many areas where the Black Rat was once the dominant species, the Brown Rat has taken over. Black Rats are slightly smaller and reproduce less often, two of the reasons this species isn’t as widespread as Brown Rats.
#39. House Mouse
- Mus musculus
Few mammals in Colorado thrive around people as well as the House Mouse!
House Mice have the characteristic large ears, thin tails, and tiny bodies of a typical “mouse.” They do incredibly well in highly populated areas, and there are now more semi-tame populations than wild.
House Mice are the most common species to find inside your home because they’re adaptable to human presence. They readily eat food scraps, build their nests in walls or dark attics and basements, and spend most of their time hidden from view. You’ve likely shared your home with a House Mouse at least once over the years. Although most people would prefer not to have them, they aren’t the worst roommates!
Like their eating habits, they are adaptable in their social behavior. House Mice with an excess of food, like those living in buildings, form a hierarchy with leaders and followers. However, in the wild, where food is less plentiful, females aggressively protect their territory from one another.
#40. White-footed Deer Mouse
- Peromyscus leucopus
Like most other mice, this species is a vector, which means it carries and spreads disease.
Many rodents can carry disease-causing pathogens without getting sick, making them ideal carriers for these germs. For example, White-footed Mice transmit hantavirus and the bacteria that cause Lyme disease.
White-footed Deer Mice are one of the most likely species you will find in your attic, garage, or basement. Even though they can spread disease, contamination isn’t very common in homes.
This is the species I’ve found in my house, and I use a live trap and release them in a field a few miles away. Here’s the trap that I use!
#41. 9-Banded Armadillo
- Dasypus novemcinctus
- Adults are about 2.5 feet long from nose to tail and weigh approximately 12 pounds.
- Their back, sides, head, tail, and outer legs are covered in bony, armor-like plates connected by flexible bands of skin.
- Tough skin and coarse hair cover the underside.
This species is one of the most unique-looking mammals in Colorado!
A common misconception is that 9-Banded Armadillos roll up into a ball when threatened. One certain armadillo species can accomplish this feat. In reality, this species is much more likely to burrow for protection.
9-Banded Armadillos have an incredible system of reproduction. Every time this species gets pregnant, the zygote splits into four identical quadruplets! They’re the only animal that produces offspring this way, and scientists aren’t sure why it happens.
Unfortunately, because of their habit of digging into lawns, many people either harm or kill them. In addition, they’re also killed often by vehicles when crossing roads. So if you find a 9-Banded Armadillo, remember to observe it from a distance and appreciate what an amazing creature you’ve witnessed!
#42. American Badger
- Taxidea taxus
- Adults range from 23.5 to 29.5 inches in length and weigh between 14 and 19 pounds.
- Their long fur is brown or black with white stripes on their cheeks and one white stripe running from their nose to the back of their head.
- They have a large flat body, short, powerful legs, triangular face, small ears, and long sharp claws.
The American Badger primarily feeds on small burrowing mammals in Colorado like ground squirrels, rats, gophers, and mice. They dig their prey out of burrows with their strong claws or enter the burrow and wait for the creature to return. Interestingly, Coyotes regularly stand nearby and wait to catch animals fleeing from badgers.
American Badgers create their own burrows as well. They regularly dig upwards of 32 feet of tunnels that reach 10 feet below the surface, with enlarged chambers for sleeping, storing food, and giving birth. Their burrows have one entrance with a pile of dirt next to it. If threatened, they back into their burrow, bare their teeth and claws or plug the burrow’s entrance with dirt.
When attacked outside the burrow, badgers will hiss, growl, squeal, and snarl. They may also release a foul-smelling musk to help deter predators. Their thick, muscular neck, loose skin, and thick fur allow them time to turn and bite or claw their attacker.
#43. American Beaver
- Castor canadensis
- Adults are 29 to 35 inches long, with a tail length between 7.9 and 13.8 inches, and weigh between 24 and 71 pounds.
- They have a dark brown coat of waterproof fur, webbed feet, and a large, flat, black tail.
- Their large, continuously growing incisors (teeth) are orange due to thick layers of enamel.
The American Beaver is North America’s largest rodent!
These incredible mammals are known as ecosystem engineers, meaning they’re one of just a few species that actively work to alter their habitat. They do so by building dams with trees, branches, and mud. Beavers use the dams for shelter, food storage areas, and dens for raising young.
Ponds created by beaver dams serve as important habitats for many types of wildlife. They also help reduce erosion and slow water movement, promoting moisture in drought-prone areas. Especially in northern climates, the water in the pond needs to be deep enough that it doesn’t freeze solid, allowing the beavers to swim under the ice all winter.
Beavers are excellent swimmers and can stay submerged for up to 15 minutes. They spend as much time as possible in the water, where they are less vulnerable to predators. This species uses its large tail to slap the water to signal danger to other beavers, as well as fat storage.
#44. Virginia Opossum
- Didelphis virginiana
- Adults measure 13 to 37 inches in length.
- Their fur is whitish underneath and dull grayish-brown on top though it varies throughout their range.
- They have white faces, long, hairless tails, and feet with opposable thumbs.
The Virginia Opossum is the only marsupial mammal in Colorado!
They occupy various habitats but generally prefer forests and thickets near a source of water. This species adapts well to human presence, so you’re likely to find them in rural, suburban, and urban environments, including your yard.
Although many people consider the Virginia Opossum a pest, they provide an important service to humans! Insects, including ticks, are a staple food for opossums. They’re incredibly good at grooming and eat 95% of ticks that try to feed on them, up to 5,000 ticks in a single season. So, the next time you’re worried that an opossum is roaming your yard, remember they reduce your chances of tickborne illness.
This species is known to play dead or “play possum,” a unique tactic they’ve become known for. They go into a catatonic state, drool, and exude a noxious substance from their anal glands, feigning death.
As marsupials, Opossums give birth to relatively undeveloped young, which they carry in a pouch on their belly until they’re more developed. The young opossums are only about the size of a kidney bean, but they crawl into the pouch without assistance. Even though litters can be made up of 25 babies, only a small percentage survive.
#45. North American Porcupine
- Erethizon dorsatum
- Adults range from 2 to 3 feet in length and weigh about 20 pounds.
- Their fur ranges in color from brownish-yellow to black, with white highlights on their quills.
- Porcupines are covered in approximately 30,000 hollow quills.
While North American Porcupines generally spend much of their time on the ground, they can also climb trees, using their tail for support. But they aren’t the best climbers; one study found that 30% of the porcupines had healed fractures from falling from trees.
They’re well known for their sharp quills used for defense. When threatened, porcupines draw up the skin of their back, bristling so that the quills face all directions. The porcupine keeps its back to the predator and moves its tail back and forth. But, despite their effective defense, porcupines are still preyed on by fisher cats, coyotes, wolverines, and other predators that have adapted to hunting them.
Contrary to popular belief, porcupines can’t throw quills at their attacker! 🙂
#46. American Ermine
- Mustela richardsonii
- Adults typically range from 6.7 to 13 inches in length. Males are twice as big as females.
- In the summer, their coat is brown on the upper parts and white underneath but turns brilliant white in winter.
- They have slender bodies, small faces, short legs, and oval ears.
American Ermines were originally believed to be a subspecies of the Beringian Ermine or Stoat (Mustela erminea). However, in 2021, a study determined that it was a unique species with distinct genetic features.
These mammals occupy various habitats in Colorado, including forested, herbaceous wetlands, grasslands, and mixed woodlands. Though they prefer to prey on small mammals, they’re quite opportunistic and will also feed on worms, insects, and berries.
Male American Ermines maintain large territories that typically overlap with multiple females. Once fully grown, males disperse to find their own territories, while females remain in their birthplace throughout their lives.
#47. American Mink
- Neogale vison
- Adults measure between 12 and 18 inches long, have 6 to 10-inch tails, and weigh between 1 to 3 pounds.
- They have a long sleek body, short stubby legs, long neck, small ears and eyes, slightly webbed feet, and a long thick tail.
- Their fur is brown to black, soft, thick, and covered with oily guard hairs that make it waterproof.
The small mammals can be found in Colorado in forested areas near large water sources. Their dens are located on river banks, under logs and tree stumps, or at the base of trees. Their dens are always close to water.
Minks are voracious predators and feed on surprisingly large prey. Believe it or not, they can eat fish up to 12 inches long and kill coastal birds like seagulls and cormorants by drowning them. Their slightly webbed feet and streamlined bodies are powerful in the water, and they can swim for up to three hours without stopping! While they’re rarely far from water, they hunt on land and can climb trees.
Despite this species being regularly hunted for its fur, its population is stable. However, scientists have expressed concern about the effect of escaped domesticated Minks on wild populations. Released Minks can cause territorial issues with wild populations and may introduce weaker genetics by breeding with wild individuals.
Check out the video of a mink above!
#48. American Marten
- Martes americana
- Adults typically range from 12.6 to 17.7 inches in length.
- They have a gray head, a dark brown or black tail, a light brown back, and a cream-colored patch on their chest.
- They are long and slender with long, shiny fur, cat-like ears, large eyes, and sharp, curved claws.
American Martens primarily occupy northern forests with a mixture of mature trees. You might spot them in areas with plenty of downed deadwood and thick vegetation for cover. They are highly adapted to deep snow and are often found in high-elevation forests that experience heavy snowfall.
These mammals are some of the hardest to find in Colorado. They’re solitary, nocturnal, and somewhat arboreal, meaning they spend a great deal of their time in trees and easily move through them.
Despite being excellent climbers and adept swimmers, American Martens primarily hunt on the ground. They typically kill their prey with a bite to the back of their neck. American Martens are sometimes observed chasing their favorite prey species, which are red squirrels.
#49. Pacific Marten
- Martes caurina
- Adults typically range from 19 to 25 inches in length.
- Their fur is a pale yellow to dark brown and black on the feet and legs.
- They have dark lines extending upward from the corner of each eye, rounded ears, large furry paws, and sharp claws.
Pacific Martens live in mature and coniferous forests with abundant felled logs for denning and foraging. They’re primarily nocturnal but may also be active in the early mornings and evenings. They feed heavily on small mammals, insects, birds, carrion, fruit, and berries and occasionally exhibit cannibalism when food is scarce. This species is also known to take food from humans and is fond of sweets such as jam.
The Pacific Marten is a species of greatest conservation need. Over-trapping and logging-related habitat loss reduced their range and distribution during the 1800s and early 1900s. Today, much of their populations are isolated and fragmented, putting them at further risk of trapping, habitat loss, climate change, and hybridization with the American Marten.
#50. Black-Footed Ferret
- Mustela nigripes
- Adults are 18 to 24 inches long, including a 5- to 6-inch tail.
- Their fur is yellow-buff, lighter on the belly, and white on the forehead, muzzle, and throat, with black feet, tail tip, and face mask.
- They are slender and wiry with short legs, large ears, eyes, front paws, and claws.
Black-footed Ferrets rely on another mammal in Colorado, the prairie dog, for almost all their food and shelter.
The average Black-footed Ferret consumes one prairie dog every three to four days, eating 100 prairie dogs yearly! Additionally, this species uses abandoned prairie dog burrows as dens for protection, raising young, and food storage.
The Black-footed Ferret is now critically endangered, even though they were once plentiful across the Great Plains. The fur trade and agricultural development contributed to their population loss. However, the most devastating cause of their decline was the reduction of prairie dog populations. Farmers and ranchers targeted them, and the introduced Sylvatic plague killed high numbers.
Thankfully, in 1987, researchers found a small population of 18 black-footed ferrets and placed them in a breeding program. Today, about 150 to 220 Black-footed Ferrets are released into the wild from captive breeding programs each year, and their populations appear to be slowly growing.
#51. Long-Tailed Weasel
- Neogale frenata
- Adults range from 8 to 10.5 inches long.
- They have brown upper parts and white to yellow fur on their undersides with a black tail tip, and in the northern parts of their range may become fully white in winter except for the tail tip.
- They have long bodies, small heads, short legs, and long whiskers.
Long-tailed Weasels have an extensive range across temperate and tropical habitats. They live in woodlands, open fields, farmland, and suburban areas. Usually, this species burrows in the ground, hollow logs, rock piles, or under barns, but they may also take over abandoned burrows created by other animals. Look for them near a source of water like a river or pond.
These weasels have a high metabolism and need to eat up to 40% of their body weight daily. They mainly feed on small rodents like voles, mice, chipmunks, and gophers, tracking their scent and crushing their skulls with their canines.
Long-tailed weasels are normally solitary, and they aggressively defend their territories. Unfortunately, due to interspecies aggression and predation, many Long-tailed Weasels die before they reach one year old. If they reach adulthood, they may live for several years, but their lifespan in the wild is not well studied.
#52. Big Brown Bat
- Eptesicus fuscus
- Larger-sized bat with around a 12-inch wingspan.
- Brown fur with black ears, wings, and feet. Wings are hairless.
These flying mammals are widespread in Colorado.
If you know where to look, you’ll find Big Brown Bats inside caves, tunnels, or other human structures.
Big Brown Bat Range Map
This nocturnal bat primarily eats insects, especially ones that fly at night. However, their preference is to eat beetles. The Cucumber Beetle is their favorite, which benefits farmers because these insects are terrible pests for agriculture. Many farmers in Colorado even use bat boxes to attract Big Brown Bats to their property!
Though rabies is common in all bats, research has shown the disease is rarer in this species. The reason for this fact is that many Big Brown Bats have immunity to rabies. Interestingly, researchers discovered that these rabies antibodies get passed down from generation to generation!
If you want even more information about mammals, or need help with additional identification, check out this field guide!
Which types of mammals have YOU seen in Colorado?
Let us know in the comments!