By Kris Inman EBS CONTRIBUTOR
It’s spring, and bears are beginning to emerge from their dens. About this time every year, like clockwork, you can expect to hear about the first spring bear sighting, as was recently the case in Yellowstone.
In fact, clockwork has a lot to do with it. It’s believed that photoperiod, or the lengthening of days, is a trigger for bears to begin to shake off their long winter’s sleep and emerge from their dens. But like everything in life, there are many other factors that influence a bear’s timing of emergence.
Males tend to be the first seen in the spring and, not surprisingly, females with cubs will stay in their dens longer, giving the cubs time to develop and get ready to move. In rare cases, some male bears won’t even enter a den for the winter, or will only occupy one for a very brief time. This tends to happen in more southern climates, in low snow years when there is an abundance of food, such as in years with a good juniper-berry crop or, in worst-case scenarios when unsecured food like trash and pet foods are highly available.
While denning, a bear’s heart rate and respiration slow, their body temperature drops only by a few degrees, and metabolism decreases almost by half while the bear lives off of fat reserves. The fat is converted into protein so the bear can make it through the long winter months.
New technology has helped us gain more insights into a bear’s physiological changes and cycles. Subcutaneous heart-rate monitors in radio-collared black bears found heart rates follow a cycle. Heart rates are at the highest in summer with 70-90 beats per minute. As summer moves into fall, the rate begins a slow decline to approximately 40 bpm. During hibernation, heart rates are at their lowest—an average of 20 bpm—which incrementally rises to 30 to 45 bpm as bears emerge in the spring. A recent study in Alaska found it took two-to-three weeks for their metabolism to return to normal after den emergence.
So as our days grow longer and bears are awakening, it’s an excellent time to think about the chance of seeing bears again. Dust off your bear spray, check the expiration date and carry it while recreating. Be sure you have a bear-resistant trash can that is working correctly, and if it isn’t, call your trash company to have it fixed—this is often built into trash-service fees. Do your part and be bear smart.
Don’t forget to post photos of bear sightings on social media and tag #bernadettebear and follow Bernadette Bear on Instagram @bearsmartbigsky. Help support Bernadette in her campaign to create a more bear-safe and bear-aware community in Big Sky.
Kris Inman is the community partnerships coordinator for the Wildlife Conservation Society and oversees the Bear Smart Big Sky campaign.
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