When winter descends, bears retreat to their dens. This natural process, often called hibernation, raises questions about what happens if this deep slumber is interrupted. Disturbing a bear during this time is ill-advised, as it can have serious consequences for the animal and pose risks to humans.
The Science of Bear Torpor
Bears do not truly hibernate like smaller mammals; instead, they enter a state of torpor or winter lethargy. This adaptation conserves energy when food is scarce. Their body undergoes significant changes. Heart rate can drop dramatically from 40-50 beats per minute (bpm) to as low as 8-12 bpm.
Metabolic rate decreases to about 25% of its normal summer rate. While body temperature reduces slightly, from around 100°F to 88-90°F, they remain somewhat responsive. This state enables bears to survive for over 100 days without eating, drinking, urinating, or defecating, as they efficiently break down stored fat and recycle urea into protein.
Impact on the Bear’s Well-being
Prematurely waking a bear from its torpor can have serious negative effects on its health and ability to survive the winter. Arousing from this reduced metabolic state demands substantial expenditure of stored energy, depleting the bear’s fat reserves faster than if undisturbed.
Bears lose between 20% to 30% of their body weight during their winter rest, relying solely on fat accumulated in the fall. An unexpected awakening can lead to increased stress and exhaustion, potentially leaving the animal with insufficient energy to last until spring when food becomes available. If a bear wakes up too early and cannot find food, it faces a heightened risk of starvation.
Encountering a Disturbed Bear
A bear disturbed from its den may react in ways that pose a danger to humans. While a bear might initially appear groggy or disoriented when roused, it can quickly become stressed and defensive. Bears are instinctively protective of their dens, especially if cubs are present, and may perceive any intrusion as a threat.
Despite their slowed metabolism, bears are not in a coma; they remain highly alert and can awaken relatively quickly. If a bear feels threatened or cornered, its natural instinct is to defend itself, which can result in aggressive behavior. Even after months of inactivity, a bear’s muscle mass and bone density are largely preserved, making them physically capable of defending themselves.
Safe Practices Around Bear Dens
To ensure safety for both humans and bears, exercise caution and respect wildlife habitats. If you suspect you have found a bear den, leave the area immediately and quietly. Should a female bear be inadvertently flushed from a den, do not approach the den site; instead, note its location and leave promptly.
Bear dens can be found in various locations, including:
- Hollow trees
- Under root masses
- In brush piles
- Rock crevices
- Excavated burrows
- Under buildings
Signs indicating a den may include:
- A depression of 2-4 feet in diameter
- Bedding material like leaves or branches
- Tracks
- Disturbed vegetation
- Claw marks
- A musky odor
When hiking in bear country, stay on marked trails and make noise to prevent surprising a bear. If an encounter occurs, slowly backing away without running, making yourself appear large, and never approaching the animal are recommended actions. For concerns about a bear den, contact local wildlife authorities.