Colorado is home to a diversity of squirrel species. There are four main types of squirrels that can be found living throughout different regions of the state: fox squirrels, Abert’s squirrels, red squirrels, and ground squirrels.
Fox Squirrels
The fox squirrel (Sciurus niger) is the most common and widely distributed tree squirrel in Colorado. Fox squirrels have predominantly gray fur with orange undersides and white patches on their noses, feet, and tails. They have large bushy tails. Adults range in size from 18-27 inches long and can weigh up to 2 pounds.
Fox squirrels are found throughout the eastern plains and mountain foothills of Colorado up to 8,500 feet in elevation. They prefer open woodlands with large trees like cottonwoods, oaks, and maples where they can find cavities to build their nests. Fox squirrels eat tree buds, seeds, nuts, flowers, some insects, and fungi. They mate in early spring and females typically have 1-5 young after a 44 day gestation period.
Abert’s Squirrels
The Abert’s squirrel (Sciurus aberti) is found throughout the higher elevation Ponderosa pine forests of Colorado. They have grayish fur with white undersides and large bushy ears. Adults are around 20 inches in length. Their most distinguishing feature is their long, fluffy tails which can be up to a foot long.
Abert’s squirrels are closely linked with Ponderosa pine trees and rarely venture far from this habitat. They rely on the seeds within Ponderosa pine cones as a main food source and also eat mushrooms, some tree bark, and other foods they can forage in the forest. Abert’s squirrels mate in early spring and females give birth to 2-4 young after a gestation period around 38 days.
Red Squirrels
The North American red squirrel (Tamiasciurus hudsonicus) inhabits coniferous forests across the mountains of Colorado. They have reddish fur on the their backs and white fur on their undersides. Their small rounded ears sit high on their head. Adults range from 11-15 inches long including their tail of 4-6 inches.
Red squirrels thrive at higher elevations between 8,000-12,000 feet where there are stands of spruce, fir, and pine trees. They nest in tree cavities or in nests known as dreys that they build out of twigs in the branches. Their diet mainly consists of conifer cones and seeds, mushrooms, some tree bark and buds, and occasionally insects or bird eggs. Red squirrels mate in early spring and females can have up to 8 young after a 36 day gestation.
Ground Squirrels
There are several species of small ground squirrels that inhabit Colorado including the thirteen-lined ground squirrel (Ictidomys tridecemlineatus), Uinta ground squirrel (Urocitellus armatus), and the Wyoming ground squirrel (Urocitellus elegans). As their names imply, these squirrels all make their homes in underground burrow systems instead of up in trees.
The thirteen-lined ground squirrel has brown fur with 13 alternating brown and white stripes down its back and a white underside. Adults reach about 11 inches in length including their very short tail of 2 inches. Uinta ground squirrels are a bit larger and lack the distinctive striping pattern. Wyoming ground squirrels have more grayish coloring with flecks of black. All three species thrive in open grasslands, meadows, and prairies across Colorado below 9,000 feet in elevation where they can dig extensive tunnels and burrows.
Ground squirrels are omnivorous and eat a combination of seeds, roots, berries, grasses, sometimes insects or even small mammals. They hibernate during the winter and mate shortly after emerging in early spring. Females give birth to about 5-10 young after a 28-31 day gestation. The young ground squirrels emerge from the burrows at around 6 weeks old.
Habits of Colorado’s Squirrels
While different squirrel species in Colorado rely on diverse habitats to support their needs, they share some common behavioral traits. All squirrels are diurnal, meaning they are active during the day and sleep at night. They forage for food in the mornings and evenings. Squirrels do not hibernate, but some species like ground squirrels will estivate or become less active during the hottest and driest parts of the summer.
Squirrels are fast and agile, able to quickly leap between trees and bound across the ground. Their sharp claws allow them to scramble up tree trunks with ease and a flexible spine enhances their mobility. Squirrels communicate through different vocalizations like chirps, squeaks, and alarm calls. They also participate in physically energetic mating rituals known as “rutting chases”.
Cheek pouches allow squirrels to temporarily store and transport food items to cache sites where they bury nuts and seeds for the winter. Squirrels have excellent spatial memory to recover thousands of caches across their home range. Their bushy tail provides balance and signaling functions and also helps regulate body temperature.
Threats to Colorado’s Squirrels
The main threats facing Colorado’s native squirrel populations include:
- Habitat loss – Deforestation, development, and wildfires can destroy trees and burrows squirrels rely on for shelter and breeding.
- Climate change – Drought and changing seasonal cycles may disrupt food availability.
- Predators – Hawks, coyotes, foxes, bobcats, and others prey on squirrels.
- Hunting – Fox and Abert’s squirrels are legally hunted in Colorado during certain seasons.
- Diseases – Squirrels are prone to mange, botflies, viral infections, and other diseases.
- Vehicles – Squirrels are often hit by cars when crossing roads.
Several Colorado squirrel species have declined locally due to these factors. However, none are currently considered threatened or endangered in the state thanks to regulated hunting and sufficient population numbers.
Interactions with Humans
Squirrels readily adapt to living in close proximity to humans. They will take advantage of urban parks, yards, and landscaping as habitat. Squirrels in neighborhoods become accustomed to people and can even be hand fed. Some key points about squirrels and humans include:
- People intentionally and unintentionally provide food sources squirrels take advantage of such as bird feeders, gardens, trash bins, and pet food.
- Squirrels will chew on structures, furniture, outdoor lighting, and other objects, causing damage.
- Squirrels serve as prey for many highly valued game species like hawks, coyotes, bobcats, and lynx.
- Watching and feeding squirrels provides enjoyment, stress relief, and connects people with nature.
- Squirrels spread their cached nuts and seeds, assisting with reforestation and new plant growth.
- In Colorado, regulated squirrel hunting is carefully managed to balance recreation and conservation.
Overall, squirrels enrich Colorado’s ecosystems and human communities when balanced relationships are cultivated. Managing conflicts through exclusion methods and understanding squirrel behavior helps foster positive coexistence.
Conclusion
Colorado is inhabited by a diversity of squirrel species adapted to forests, mountains, prairies, and other habitats statewide. Fox squirrels, Abert’s squirrels, red squirrels, and ground squirrels fill important niches as prey species and seed dispersers. Their energetic behavior and adaptability allow squirrels to thrive around humans when their needs for shelter, food, and space are met.
Appreciating Colorado’s squirrels requires acknowledging the challenges they face from threats like habitat loss and celebrating the vitality they add to natural environments. Providing squirrels room to roam within balanced ecosystems ensures future generations can enjoy observing these agile rodents scurrying through the treetops and across the forest floor.