When winter arrives, many animals adapt to colder temperatures and reduced food availability by entering a state of dormancy. For bears, this period is often referred to as hibernation, though it is more accurately described as a deep sleep or torpor. This extended period of inactivity serves as a survival strategy, allowing these large animals to conserve energy when resources are scarce.
Hibernation Timing in Arkansas
American Black Bears (Ursus americanus), the species found throughout Arkansas, typically enter their dens in late fall or early winter. Den entry for bears in the state generally occurs between November and December, though some may wait until early January. The precise timing can vary year to year based on environmental cues and individual bear characteristics.
Bears in Arkansas usually emerge from their dens in early spring, typically during March and April. The duration of this denning period can range from approximately 100 days to over 150 days. Female bears, particularly those that are pregnant, are observed to enter dens earlier than males and non-pregnant females, and they tend to remain denned for a longer duration. Cubs are born in the den during January or February, with mothers and their young being among the last to emerge, often in mid-April.
Factors Affecting Hibernation
The timing and length of a bear’s denning period in Arkansas are influenced by several factors. Food availability plays a significant role; a robust autumn crop of acorns, nuts, and berries can allow bears to delay denning as they continue to forage. Conversely, a scarcity of food sources can prompt an earlier entry into the den.
Weather conditions, such as decreasing day length, cooler temperatures, and snow accumulation, also signal the onset of the denning season. A bear’s physiological state, including its age, sex, and reproductive status, also dictates its denning schedule.
The Hibernation State
During their denning period, American Black Bears undergo significant physiological changes. Their heart rate can drop substantially, from a typical 40-50 beats per minute (bpm) during active periods to as low as 8-21 bpm. Metabolic rates decrease to about 25-50% of their summer levels, allowing them to conserve energy efficiently.
Unlike true hibernators, a bear’s body temperature only drops slightly, typically by 10-12 degrees Fahrenheit, maintaining a range of 88-98°F from their normal 100-101°F. This relatively higher body temperature allows them to be more easily aroused, a protective mechanism, particularly for females with cubs. Bears sustain themselves entirely on stored fat reserves, and they do not need to eat, drink, urinate, or defecate during this time, often forming a “fecal plug.”
Before and After Hibernation
Before entering their dens, bears engage in a period known as hyperphagia. In the fall, bears consume vast amounts of high-calorie foods like nuts and berries to build up substantial fat reserves. This intense feeding allows them to gain significant weight. Simultaneously, bears actively search for and prepare suitable den sites, which can include rock crevices, hollow logs, or brush piles.
Upon emerging from their dens in the spring, bears are often sluggish as their bodies gradually adjust to normal metabolic rates. This initial period is sometimes called “walking hibernation.” Their immediate priority is to find food, and they will seek out easily accessible sustenance such as newly growing plants or carrion. They also drink water to rehydrate. Over the subsequent weeks, their activity levels increase, and they progressively return to their regular foraging behaviors.