Black bears in Colorado undergo a period of reduced activity during the colder months to conserve energy when food is scarce. Often referred to as hibernation, understanding this biological rhythm is important for residents and visitors in bear country.
When Bears Emerge in Colorado
Black bears, the only species in Colorado, typically emerge from their winter dens as early as mid-March and continue through April. While some bears may become active in late April or early May, this reawakening signals the start of their active season, which usually lasts until early November.
Male bears generally exit their dens first, often in mid-March. Female bears, particularly those that have given birth to cubs during the winter, emerge later. These sows with their new cubs may not leave the den until late April, allowing their young to develop further before facing the outside environment. Bears in Colorado enter a state of torpor, a lighter form of hibernation, which allows them to occasionally wake up during the winter months.
Factors Influencing Emergence Timing
A black bear’s emergence timing is influenced by several environmental and biological factors. Warmer temperatures and an early spring can prompt bears to cut their dormant period short, leading to earlier activity. Snowmelt and potential den flooding can also contribute to an earlier exit.
Food availability plays a significant role in determining when bears become active. Bears do not hibernate primarily because of cold, but rather due to the reduced food supply during winter. They emerge from their dens hungry, having lost between 15% and 40% of their body weight. The scarcity of natural food sources in early spring can drive them to seek sustenance elsewhere, sometimes leading them closer to human-populated areas. Bears in areas with human food sources tend to emerge earlier, as these offer consistent calories.
Post-Hibernation Behavior and Safety
Upon emerging from their dens, black bears are driven to find food and replenish weight lost during their winter dormancy. Their keen sense of smell aids them in this search. Initially, their diet consists of tender, new vegetation such as grasses, aspen buds, and young leaves, to reactivate their digestive systems. They also consume insects like ants and beetles, along with any carrion they discover. This early period is sometimes referred to as “walking hibernation,” as bears move slowly and primarily consume vegetative material to prepare their bodies for a more diverse omnivorous diet as the season progresses.
Living in bear country requires adherence to safety guidelines, especially during the spring when bears are most active and seeking food. Many human-bear conflicts arise from bears accessing human food sources, including garbage, pet food, and bird feeders. To minimize these encounters, secure all trash in bear-resistant containers and only place garbage out on the morning of pickup. Bird feeders should be removed from April through November, and grills should be cleaned after each use.
When recreating outdoors, be aware of your surroundings and remain calm if you encounter a bear. Slowly back away, ensuring the bear has a clear escape route, and speak in a normal voice. Never run, as this can trigger a chase response, and avoid direct eye contact. If a bear approaches, stand your ground, make yourself appear larger by waving your arms, and make loud noises such as yelling or clapping to try and scare it away. Keep pets leashed to prevent encounters.