Many people associate bears with a long winter’s sleep, often referred to as hibernation. While wild bears do undergo a profound change in their behavior and physiology during colder months, the experience for bears residing in zoos is distinctly different.
Understanding Wild Bear Winter Behavior
Wild bears enter a state often called torpor or winter lethargy, which differs from the true hibernation observed in smaller mammals like ground squirrels or bats. During this period, their body temperature only drops slightly, typically by 10-12 degrees Fahrenheit, unlike the near-freezing temperatures of true hibernators. This allows them to be roused relatively easily if disturbed.
Physiological changes are significant, including a dramatic reduction in metabolic rate, often by 50-60%. Their heart rate can slow from a typical 40-50 beats per minute to as low as 8-12 beats per minute, and breathing can decrease to just one breath every 15 to 45 seconds. Bears can remain in this state for several months without eating, drinking, urinating, or defecating, as their bodies efficiently recycle waste products to maintain muscle mass. In preparation, wild bears engage in hyperphagia during the fall, consuming vast amounts of food to build up a substantial layer of fat, which serves as their primary energy source throughout winter. They then seek or create dens in locations like hollow logs, rock crevices, or excavated burrows to shelter for the season.
Winter Behavior of Bears in Zoos
Bears living in zoological settings generally do not experience the same deep, sustained torpor as their wild counterparts. While they may exhibit periods of reduced activity or increased resting, their winter behavior is usually a lighter form of lethargy, often involving more sleep and slower movement while remaining awake and responsive to their environment.
Unlike wild bears, zoo bears typically do not go for extended periods without food, water, or eliminating waste. They can be observed moving around their habitats, interacting with enrichment items, and engaging with keepers, even during colder months. While some zoos encourage a more natural seasonal shift in behavior, the profound physiological changes seen in wild denning bears are less pronounced in captivity. This allows for continuous monitoring and care, which is a priority for animal welfare in zoos.
Factors Influencing Zoo Bear Behavior
The primary reason for the difference in winter behavior between wild and zoo bears is the consistent availability of food and a controlled environment. In the wild, bears enter torpor as a survival strategy to cope with scarce food resources and harsh weather conditions. Zoos provide a continuous and reliable food supply year-round, removing the evolutionary pressure for bears to undergo deep metabolic suppression to conserve energy.
Zoo enclosures often feature climate-controlled indoor spaces or shelters that protect bears from extreme cold, wind, and snow. The absence of predators or other environmental threats also eliminates the need for bears to maintain a state of heightened readiness. These factors collectively diminish the natural cues and survival imperatives that drive deep torpor in wild populations, allowing zoo bears to maintain a higher level of activity throughout the winter.
Zoo Care During Winter Months
Zoos implement specific care strategies to support the well-being of bears throughout the winter. While daily feeding continues, some zoos adjust the diet composition or quantity in the fall to encourage a more natural seasonal weight gain and a subsequent reduction in appetite during winter. This can involve offering more calorie-dense foods in autumn, followed by a decrease in overall food intake as temperatures drop.
Keepers ensure bears have access to comfortable and secure indoor and outdoor spaces, often providing extra bedding like hay for warmth and nesting. Enrichment activities are maintained year-round, though they might shift in focus during winter, sometimes incorporating more olfactory or puzzle-based challenges to stimulate the bears’ senses and encourage natural behaviors. Veterinary staff and animal care teams continuously monitor the bears’ health, weight, and behavior, ensuring they remain healthy and engaged, even if their activity levels naturally decrease during the colder period.