Yes, the American black bear (Ursus americanus) is a common, native resident of the foothills and canyons directly bordering Boulder, Colorado. The city’s unique geography, where the Rocky Mountain Front Range transitions immediately into the urban environment, creates a significant wild-urban interface. This proximity means black bears frequently move into residential areas, especially when driven by seasonal needs. Coexisting with these large animals is a reality for residents and visitors, requiring awareness of their behavior and proper precautions for both human safety and bear conservation.
Confirmation of Black Bear Presence and Range
The only bear species found in Colorado is the American black bear, as the grizzly bear was extirpated from the state decades ago. While called “black” bears, their coloration varies significantly, often displaying coats that are brown, cinnamon, or blond. These omnivores primarily inhabit the western foothills and the extensive Open Space and Mountain Parks (OSMP) lands surrounding Boulder. Because the city sits on the edge of this natural habitat, bears routinely travel through greenbelts and into neighborhoods searching for food and shelter. With an estimated population of 12,000 animals in Colorado, data shows their presence is expanding eastward, increasing the frequency of sightings deeper within Boulder’s urban core.
Seasonal Behavior and Urban Attraction Factors
Seasonal Behavior
A black bear’s active season runs from early spring until they den for hibernation in late fall or early winter. Late summer and fall are the peak times for urban bear sightings, driven by hyperphagia. During this period, bears must consume up to 20,000 calories a day to build the fat reserves needed to survive hibernation. This intense caloric need draws them into urban environments where high-calorie, easily accessible food sources are abundant.
Urban Attractants
Unsecured trash and compost are the number one attractant, accounting for nearly 80% of bear sightings where an attractant was identified. The smell of garbage is a powerful lure, and a bear finding a reliable food source in town is likely to return repeatedly. Other common food rewards include bird feeders, hummingbird feeders, pet food left outdoors, ripening fruit, and exposed compost materials. Easy access to these human-provided foods causes bears to become habituated, meaning they lose their natural fear of people and associate humans with a meal. This habituation increases the risk of negative human-bear interactions and results in higher mortality rates for the bears involved.
Coexisting Safely: Home and Trail Practices
Home Practices
Reducing access to human food sources is the most effective action residents can take to prevent conflicts and protect the bear population. Boulder mandates the use of bear-resistant containers for trash and compost in certain areas, and everywhere if waste is placed out the night before collection. Properly securing waste means using approved containers with latches or storing bins in a locked building until the morning of pickup. Beyond trash, several other attractants must be managed:
- Remove bird feeders entirely from April to November, as spilled seeds attract bears.
- Harvest all ripe fruit from trees immediately.
- Secure backyard livestock, such as chickens or bees, with electric fencing or reinforced enclosures.
- Lock ground-floor windows and doors, as bears are intelligent and can open car doors and sliding glass doors.
Trail Practices
When recreating on Boulder’s Open Space trails, hikers should take precautions to avoid surprising a bear, such as making noise by talking or singing. Dogs must be kept on a leash to prevent them from chasing or provoking a bear. If a bear is encountered, remain calm, avoid direct eye contact, and back away slowly while talking in a low voice. Never run, as this may trigger a chase response; instead, make yourself look large and prepare to fight back if the bear attacks. All bear sightings and incidents should be reported to Colorado Parks and Wildlife (CPW) or the city’s non-emergency line, especially if a bear is threatening safety or destroying property.