How much do bears eat before hibernation?
The grandiose contenders of the Katmai National Park “Fat Bear Week” got us a little curious about hibernation diets.
Beadnose, the sumo-sized brown bear pictured above, is a resident of Katmai National Park in southern Alaska and a contestant in the park’s annual Fat Bear Week. Every October, as the bears prepare for a winter of hibernation, Katmai hosts a social media competition where the public get to vote on “which bulky brute deserves the title of Fattest Bear”.
Contrary to popular belief, bears not actually fully hibernate during winter. “True hibernation” is characterised by a prolonged period of deep sleep, where an animal will lower its body temperature, breathing rate, heart rate and metabolic rate. While most animals cannot be easily woken from a state of hibernation, bears will arise quickly if threatened by predators — or, remarkably — to give birth. This sleeping state is known as torpor and is generally observed in larger hibernating animals that are unable to fully drop their body temperature to match that of their wintery surroundings. The body temperature of hibernating bears will generally be around 31°C (88°F), while smaller hibernators may drop down to 4°C (40°F). At this level, a small sleeper would probably get eaten by a predator before warming up enough to react to its threat.
Before proceeding with our culinary discussion, let us first answer a few burning questions about bear hibernation (courtesy of The National Park Service):
- Do bears pee during hibernation? Nope, bears will not eat or release any bodily waste during torpor. Instead, bears engage in a magical process of fat metabolism, where nitrogen from waste urea is used to build up proteins. That’s right, bears can turn fat into muscle mass.
Of note, many true hibernators like bats, ground squirrels, mouse lemurs, snakes, and marsupials will wake every few weeks to nibble on stored snacks and pass waste. - How long do bears hibernate for? This highly depends on location and the harshness of the winter period. Hibernation “varies from a few days or weeks for black bears in Mexico to 6 months or more for bears in Alaska.”
- Why do bears hibernate? Hibernation is a nifty evolutionary tactic to protect animals from harsh winter conditions. By storing food and dropping their metabolic rate, hibernators do not need to search for tasty treats when supplies are scarce.
- Where do bears hibernate? Bears build dens during the Autumn months. Exact specs depend on the type of bear in question, but the job will generally get done in about 3–7 days, during which the bear may excavate over a ton of material. Once complete, the bear will lay out an insulating layer of bedding consisting of leaves and other scraps found in the immediate surroundings.
- How long is a bear’s post-hibernation recovery period? Very understandably, bears will emerge from their six-month nap in a state of walking hibernation that may last for several weeks.
Bears are some of most omnivorous animals on the planet with about 80% of their diet consisting of nuts, berries, fruit, leaves, and roots. For the remainder, bears will feast on a wide range of animals, from small rodents all the way up to moose. The roughly 2,200 bears in Katmai National Park are known to feast off the major salmon run in the Brooks River.
In preparation for hibernation, bears may eat north of 40kg (90 lbs) of food per day. Before laying down to rest, the top performers may bulk up by a staggering 450–550kg (1000lb-1200lbs), effectively doubling their body weight. What’s even more impressive is that the bears will loose this mass, plus up to 15–30% of their body weight after a single winter’s sleep.
We wholeheartedly share the envy and frustration of our readers with busy gym schedules and fat-conscious diets.
