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Do Black Bears Hibernate?

Burrow style bear den

Yes! You may also see it called denning, torpor, and carnivore lethargy.

Hibernation is the state in which an animal’s metabolic and physical activity is reduced. During this time, bears do not need to eat, drink, urinate, or defecate.

This period of reduced activity occurs in all black bear populations. Hibernation is brought on by many factors, including reproductive status, amount of daylight, and temperature change and, most importantly, food availability.

However, it is notable that bears in southern states den for shorter periods and sleep less deeply than bears in colder climates. While denned bears in northern states are very lethargic and less responsive to people, bears in the South may readily run away if they are disturbed. In addition, male bears in southern states like Florida may have a reduced denning period or none at all but will exhibit lethargic behavior.

Did you know?

Due to a bear’s remarkable ability to prevent osteoporosis, renal failure and other health complications during hibernation, there is ongoing research of how bear hibernation could help the treatment of those diseases in humans.

What Makes a Den?

In Florida, while males and females that are not pregnant may den in dense vegetation for only a few weeks or a month, pregnant females must den for the winter to have cubs.

Because their cubs will be born in the den and nursed there for over 2 months, pregnant females often select more protected sites than other bears. Dens are commonly made on the ground in dense thickets but have also been found in tree cavities and under fallen trees or logs.

Breeding and Reproduction

Male bear on the left, female bear on the right

Bears are considered sexually mature between 3 and 4 years of age. In Florida, the breeding season for black bears runs from June to early August. Bears have a breeding adaptation that is called "delayed implantation", where the eggs are fertilized in the summer but only develop to the blastocyst stage and do not implant in the uterine wall until late November or early December. If the mother is in poor condition, the fetus will not continue to develop or the female will miscarry. A female in better body condition will have a larger litter of cubs. This adaptation to periodic food shortages prevents the female from producing more offspring than she can handle.

Did you know?

Black bear milk can contain up to 30% fat while they are nursing their cubs, compared to whole cow milk that is 3-4% fat.

The Bear Cub

Bear Scat

Bear cubs are very small at birth, only 8 - 15 ounces (225 - 450 grams), about the size of a can of soda.

Newborn cubs have a very fine coat of hair and their eyes are closed. The average litter size in Florida is 2 to 3 cubs, but litters with 4 cubs have been documented. Litters of 5 or even 6 cubs have been seen in other parts of the species range, but not in Florida. can range from 1 to 5.

The cubs nurse in the den until April and continue to nurse for several months after they emerge from the den. They are weaned in the fall and spend their first summer and fall learning from their mother how to forage and be a wild bear. They will usually den with her the following winter.

Bear cub in den

Adult females will typically breed every other year. Bear cubs stay with their mother until the summer of their second year, so although young bears may be called “cubs” when they are still with their mother, you may also see them called "cubs of the year" when they are small and less than a year old, and "yearlings" after their second winter.  Yearlings may be called ‘dependent yearlings’ when they are still with their mother.

During their second summer, the family group separates. Female yearlings will likely establish a home range that is near or overlapping their mother’s, while male yearlings are likely to disperse a longer distance to find new areas well away from their mother's home range.