Fun Facts about Grizzly Bear Hibernation

Bears have adapted to thrive in locations with harsh winter conditions. By eating a lot of food while it is plentiful, grizzly bears can live off body fat during the winter, when food is scarce. According to research, bears hibernate for 5-7 months every year. 

Wildlife enthusiasts do not want to miss the chance to experience Yellowstone Bear World, where they can learn more about grizzly bears’ adaptations and behaviors. 

Bears gain 3 pounds each day

As they prepare for their months-long hibernation, grizzly bears begin to eat an exorbitant amount of food in the fall, gaining about 3 pounds each day leading up to their hibernation period. This is known as hyperphagia. 

In order to ensure a successful hibernation, grizzly bears need to eat about 20,000 calories in the feeding frenzy. Bears that successfully meet the caloric minimum can survive on fat stores for their entire hibernation period.

As the winter months approach, grizzly bears begin to eat less, drinking large amounts of water in an effort to purge themselves of wastes before hibernation.

Pregnant bears in hibernation

For grizzly bears, mating season begins in May and can last through late June. While most mating occurs in June, the implantation of fertilized eggs does not occur until months later, delayed to allow for a successful denning season in preparation for hibernation. This allows female bears to preserve their energy during hibernation. 

Additionally, bears have control of their populations in the event that there is not enough food for survival. Fertilized eggs will only attach to the uterine wall if the bears reach a sufficient body fat percentage or weight during the summer and fall. If these conditions are not met, the fertilized eggs will not attach or progress past blastocysts. 

Hibernation is a slow process

Yellowstone National Park visitors may be surprised to see resident grizzly bears up and about during the late stages of hibernation. As temperatures drop into the negatives, they will slowly settle in for their annual hibernation, where their heart rates and breathing rates drop significantly.

Bears dens can withstand extreme temperatures

Each bear is responsible for digging its own den, and grizzly bears typically dig a new den every year.  Over 3-7 days, grizzly bears dig up to a ton of natural material and collect bedding material, such as tree boughs, to create a heat-efficient den that can withstand temperatures as low as -60°F in Yellowstone National Park. 

Grizzly bears prefer digging dens in high elevated slopes with an entrance small enough to squeeze through. This way, they will insulate them faster. The chamber is almost the size of their bodies to facilitate the retention of heat, creating the ideal conditions to retain heat during hibernation.

Hibernation can contribute to medical breakthroughs

Experts are taking a closer look at bear hibernation to assist in making medical advancements to treat diabetes and osteoporosis. Studies can also help people experiencing kidney failure and other conditions that impact human organ viability. 

Using hibernation to move humans to mars

During hibernation, while their breathing and heart rate slows significantly, grizzly bears carry on with normal metabolism. Scientists can study these adaptations with the purpose of sending people to Mars and other planets, putting them into a medically-induced hibernation for the journey.

Grizzly bears are adapted to live in different conditions ranging from elevated alpine environments to sea-level locations. No matter their elevation, they must hibernate for several months each year to survive cold conditions and scarce food supplies. 

Contact Yellowstone Bear World to schedule an appointment online or by phone at 208-359-9688 to see black bears and their famous grizzly bears.