Here at AWCC, we often get asked if our bears dig their own dens, so today we’re providing some interesting brown bear facts regarding winter and hibernation. While our black bears have dens we’ve made for them, our brown bears love to make their own. In the featured photo you can check out Patron’s recent handy work in preparation for her winter’s rest. Patron did the majority of the work on this den, digging tirelessly day after day to ensure she had a nice, warm place to hunker down for the winter. However, this did not stop JB and Hugo from making themselves at home and taking advantage of her hard work!
In the wild, brown bears typically dig new dens every year. The den entrance is just large enough for the bear to squeeze through so it will cover quickly with insulating snow. The chamber is dug only slightly larger than the bear’s body to allow for maximum heat retention. A female bear will also give birth in their den. Cubs will stay with mom for up to 3 years, meaning cubs will hibernate with mom up to 2 more times after the season of their birth. After mating season in June/July, female bears exhibit delayed implantation. This means a fertilized embryo does not implant in the female’s uterine wall until she enters her den. If the female has not gained adequate weight to support reproduction, implantation will not occur. After 60 days gestation, two to three cubs are born in the den. Birth can occur as early as December, and others as late as February or March.
While asleep in their dens, a brown bear’s heart rate, respiration, and body temperature drops. Brain activity continues in bears throughout the winter and they can be easily woken up. Instead of true hibernation, a bear’s winter rest is actually called ‘torpor’. Now you know!