The first Yellowstone grizzlies to come out of hibernation this year were spotted on February 22. Last year it was February 9. Alberta bears are waking up, and so are Connecticut’s. All across North America, our hirsute friends are yawning, scratching nether regions, and poke their heads out the doors. Why? And why now?
Because bears wake up pretty much for the same reason we do: the smell of coffee and bacon.
For the most part, the availability of food determines when a bear drags his butt out of the den. This is instinctually hard-wired, though a wicked sense of smell helps things along. It makes sense that the spring wake-up call comes at different times depending on the region. In the arid and/or snow-packed West, Yogi may bed down for over six months, hitting the hay as early as September and waking up when the tulips are pushing in April-or at least that was the seasonal pattern before climate change. Where food is plentiful, say the Southeast, bears might party it up until December and only stay in for about three months or so.
Hibernating is easy. Prepping for it? Not so much.
How do they chill for so long? It’s not because of Netflix. Hibernation for bears is less like the endless, deep sleep that we humans romanticize, and more like falling asleep in a hammock when you know you don’t have any responsibilities. A bear’s entire metabolic system slows down, as they survive off the fat they worked so hard to put on the previous season. Blood flow, heart rate, and oxygen use drop by nearly half of their summertime needs.
An adult bear still processes several thousand calories a day (approximately 4,000 kcal for black bears) during hibernation, even though most non-essential bodily functions slow or stop. What’s non-essential? Pooping, peeing, eating, drinking.
You can’t keep a good bear down. Despite everything you’ve ever learned, there is a debate about whether or not bears are true hibernators. All hibernating animals go into a slowed down state called torpor, but only true hibernators experience massive drops in body temperatures. Those guys are down for the count. A bear’s body temp in the den averages only 12 degrees F below normal. Chilling around 88 degrees F means they’re still capable of moving around, occasionally even taking a mid-winter stroll outside.
With the movement and body temp in mind, biologists in one corner won’t concede that bears are true hibernators. In the other corner, some biologists vote for bears as “The World’s Best Hibernators” because their bodies are so damned efficient in torpor that they don’t need a lower temperature. Confused yet? You do not want to get in a bar fight with a biologist. Just know that you’re safe saying black bears and brown bears hibernate, or that they go into hibernation. Anything else might get people riled up.
Bears: They’re just like us. Waking up from hibernation is brutal. You know that time between the final concession to the snooze button and when the first jolt of caffeine courses through your veins? Imagine if that took two or three weeks. Since bears don’t have the option of getting hooked on coffee, they spend those weeks in what is known as “walking hibernation.” Slowly, their metabolic processes and body functions ramp back up to handle their summer-levels of activity. Very much walkers from The Walking Dead.
The critical post-hibernation eat-a-thon. Regardless of the region, most North American bears will be out their dens as the green of spring hits full swing. After the grogginess of walking hibernation passes, they’re ready to eat and drink. Being merry is the least of their worries during this spring smorgasbord. At this point, they’re at serious risk of dehydration if they can’t find water. Plus, they need food to refuel their bodies with more daily calories than they were using throughout the winter.
During hibernation, bears metabolize fat to fuel the mandatory physiological processes like breathing. Skinny and weak after a few months of this, their bodies start eyeing muscle as a fuel source. The bears need to ingest enough calories to continue metabolizing fat and prevent their bodies from breaking down muscle. If they’re unable to find enough food relatively quickly, the risk is a deadly nitrogen build-up in the bloodstream.
Vegas does not have a buffet big enough. Seeing as it’s only spring, we’re getting ahead of ourselves. But to every yin, there is a yang. And to every restrained hibernation, there is a no-holds barred eating frenzy later in the summer. Hyperphagia is the technical term for when bears gorge. It’s a beautiful time of near-unlimited food and water intake to prep for the next hibernation. The bears are running on all cylinders, with metabolic processes at optimum throttle. If food is available, bears will eat it – black bears take in 15,000 – 20,000 kcal each day. Eating and drinking becomes a full-time job.
Shuttin’ her down. With a little extra around the middle, bears slow down their eating in the fall – about the same time their food supply starts to dry up for winter. Less food makes them a little lazier, as anyone who has seen a bear in fall can attest. Unless a human is being a jackass, bears simply cannot be bothered to get riled about us in the fall. Then again, black bears rarely care about us other than to get the hell away. Grizzlies may feel differently. While eating slows, hydrating does not. Bears in this transition time drink water and pee like nobody’s business. It’s the most effective way to flush their bodies of toxins and wastes before bedding down for a few months.
No Ambien. No thousand dollar mattress or fancy sleeping bag. No messing with daylight saving time. Bears’ sleep patterns are established by a good old healthy mix of food, exercise, and the seasons. We have so much to learn.