Bear-ly to Bed, Bear-ly to Rise
Every time my dad and I chat on the phone to catch up, he asks after Wally, the black bear here at Osborne. About this time of year he starts asking if the bear has gone to sleep yet; in a few months he’ll start asking me if it’s awake yet.
I think we’re innately fascinated by animals’ ability to soldier through the winter using nothing but their birthday suit. The bear piques most peoples’ interest, since he’s the only true hibernator in our menagerie (or, maybe he’s not, more on that in a minute), but in reality, all of them display some pretty fascinating behaviors.
The raptors, for instance, often decline their food during especially cold spells. Their talons and beaks have plenty of strength to deal with frozen prey, but for whatever reason when we get a polar vortex they seem less excited for meal time.
It’s counterintuitive since the raptors are warm-blooded. Homeothermy depends on calories to burn. Livestock owners know that their cows will need additional food to stay happy and healthy through the colder months. This little observation in our wildlife exhibit is not a phenomenon I can find any primary source literature about; anecdotally, I see plenty of raptors out hunting or scavenging all winter.
Do wild birds actually eat less in the winter, and nobody notices? If so, why? If not, then what’s with the hunger strike here at Osborne?
I can’t even come to a totally satisfying guess. For just about every other warm-blooded creature, including myself, the winning strategy to survive the winter is A) eat a whole lot of calorie-rich food and B) sleep a lot.
But each animal balances those demands a little differently, so perhaps the birds have some unusual calculus that makes eating their food less adaptive than waiting out the cold snap.
The other animals have a much more sensible approach. The fox wraps his big, fluffy tail around his body and finds somewhere to shelter from the wind. If the sun is shining, all the better.
The bobcat and mountain lion don’t change much. They’re cats, so it’s hard to carve out any additional hours in the day to be spent sleeping. They do eat a little more vigorously, and spend a little more time in their straw-lined little houses, but by and large they remain the same kinda-testy little hypercarnivores they are all summer.
The wolf definitely exhibits a noticeable change in behavior, but quite different from his cohorts. There might not be a happier creature on earth than Fluffy when the weather gets truly awful. It must hearken back to his Pleistocene roots, when his ancestors would form a pack and chase elk and bison across the plains floating on the snow like Elvish folk from Lord of the Rings.
He cavorts along the perimeter of his cage, and hops up and down (but rarely in) his own straw-lined house. On the rare occasion a squirrel takes a wrong turn and ends up in his enclosure, he really makes a day of it. Most of the time the squirrel gets away, but he still looks like he had fun.
Truthfully, it’s a lot of fun to watch these animals do their thing in midwinter, with two exceptions: the raccoon, and the bear.
The raccoon disappears into her box for weeks at a time, going into a state called torpor. She’s in a deep sleep, her metabolism drops, and her daily poop-scooping turns into a much more occasional affair.
Wally, the bear, disappears for much longer. He gets a little ornery in autumn when he experiences hyperphagia, a preparatory stage for winter where he eats truly heroic amounts of food to pack on mass ahead of the long winter’s nap.
He also eats a lot of roughage and grit that time of year. Once he lays down for the winter, he doesn’t plan on getting up to use the restroom at any point. Come spring he will do what many of us do when we first wake up, but in his case it's much more interesting, and by interesting I mean gross.
Eventually, he ambles into his shelterhouse, curls up on some nice fluffy straw, and we won’t see him again until March.
But, is he actually hibernating? Well, that depends on who you ask. It turns out the concept of bear hibernation is pretty divisive among biologists. Some say bears just go into torpor – like the raccoon – but for longer.
Biologically, hibernation involves a few key elements: a drastic decrease in metabolism, heart rate, and body temperature combined with a cessation of eating, drinking, and waste elimination. Hibernation can last for months, or just a few days. Wait a minute, that sounds a lot like the raccoon…
Except, it’s pretty easy to wake Kizzy up. She won’t be happy about it, but she will respond to external stimuli. Crucially, true hibernation means these animals cannot easily rouse themselves in the event of danger.
For example, bats hibernating in a cave will not mind a caver’s headlamp shining directly in their face. You can even touch them – though you shouldn’t – without having them fly away. It takes a quite a while for them to get their body systems back online following a disturbance.
Using this operational definition, Wally falls short of a few criteria for “true” hibernation, at least compared to the remarkable drawdown of bats.
He will respond to stimuli, albeit pretty slowly. He does shift positions during “hibernation,” as all bears do to avoid developing sores on spots holding his considerable weight, while many “true” hibernators remain virtually motionless.
His body temperature drops, but not quite as drastically as a bat or a chipmunk who can have a 50°f change from summer to winter. His body temp hovers around 100-101°f during his active periods, while during dormancy it only drops to a little below 90°f.
However, many biologists have asserted that bears do hibernate – they’re just so good at it it's hard to recognize.
Wally’s resting heart rate will plummet to about 8-15 beats per minute. He might go the entire winter without rousing to eat, drink, or poop. Moreover, while he doesn’t have to hibernate (not all bears do, provided they have adequate food), research has shown that captive bears are much healthier when they can go through a period of hibernation.
The less-drastic body temperature drop might come down to simple physics. A chipmunk or a bat has a very high surface area-to-mass ratio; smaller bodies have a harder time holding onto heat since they weigh so little compared to how much skin they have exposed to cold air.
Bears, on the other hand, are huge – by far the largest animal to hibernate. Wally weighs about 330 pounds, and he’s not a particularly large bear even amongst black bears, to say nothing of grizzlies or polar bears. While animals’ volume increases exponentially with size, their surface area only grows linearly, meaning he loses less of his heat budget to radiative cooling – especially with that thick pelt.
But what about his alertness compared to a bat? Well, that might come back to the same thing. Physical activity requires a certain body temperature for muscles to contract. If a bat wants to get its flight muscles back, its going to have to spend some time under a heat lamp. Wally’s body temperature, while lower, isn’t quite low enough to stop him entirely.
So while it may look more like a light sleep, more rigorous investigations into their bodily processes reveals that whatever bears do probably qualifies as true hibernation. Their brain activity, oxygen consumption, and muscle activity all match the patterns found in other true hibernators.
Confused yet? Don’t google it, then. It only gets worse. The whole thing devolves into a level of semantics that would make Wittgenstein blush.
And does Wally even care? No, he’s asleep. That’s about all he knows. He never reads my blog posts and I’ve given him a pen and paper to write down his thoughts, but he ate them both. Hyperphagia, ya know.
That’s one of the beautiful things about nature: we try to put little boxes around the definitions of things, but it’s all a spectrum. There’s an exception to every rule. Species intergrade, like oak trees crossing pollen between a northern red oak (Quercus rubra) and a black oak (Quercus velutina). I can send a sample to a lab to find the ratio of each in the offspring, but it doesn’t change much for the tree itself.
Even within species, nature is quick to throw cold water on our dogmas. We always celebrate the first robin in springtime, except, not all of them migrate. Even the same robin might stick around one year and not the next.
It’s a reminder not to get too attached to our definitions, lest they lead us astray. There’s real, valuable insight for our species found in the wonder of hibernation-like adaptations: how could modern medicine better manage coma patients for a more complete recovery? How might the bears’ unique ability to turn their urea into protein inform the medical strategy for patients with failing kidneys? We never have to think outside the box if we don’t hop in there and close the lid. Maybe you think bears hibernate, maybe you don’t, but what matters is that they do something remarkable. The dictionary definition doesn’t matter; the observation does.
The Pony Hollow Trail 15K took place at the beginning of the month. For a race day in November the conditions were great; runners had cool but not bone-chilling conditions and we got a new course record from overall champion Kyle Wagner!
On November 6th, the Central Schools' Green Team came out for one last seed harvesting hurrah on the prairies here at Osborne. Unsurprisingly, their youthful energy quickly made a contest out of it and copious amounts of seed was the result.
The bridge at Motor Mill got it's annual holiday spruce-up, with lights laid carefully by the mill's many studious little holiday elves.
Looking Forward If you're reading this while you should be working, you still have time to sign up for tonight's (December 1st) Holiday Walk at Motor Mill! On this walk you'll encounter a few ghosts of Motor's past, including one from it's waaaay past, and even one real-life mill volunteer to tell the modern story! Call Osborne at 563-245-1516 to reserve a spot for the walk, with groups departing every 15 minutes starting at 6:00. Dress warm! On December 10th, come on down to Deb's Brewtopia and sing your heart out for a good cause! The CCCB karaoke night, hosted in partnership with the Turkey River Recreational Corridor, will raise funds to go towards the Inn renovation at Motor. The following Saturday, December 17th, Central Innovative Ag students Jordan Everitt and Nate Shirbroun will host another fundraiser for the Osborne campground, an auction right here at Osborne! Tickets are $10 and will include a dinner provided by the Edgewood Events Center. Check out the facebook event for more details.