Black Bear: MN’s largest hibernator
December 21, the Winter Solstice, marked the first official day of the winter season. Even though temperatures are well above average for this time of year, vermin persist. Oh, and boy do they persist!
Cooling and cold temperatures drive little furballs indoors: into our homes, cars, garages, barns, and walls. Rodent season is in full swing. At night (and during the daylight hours!) a gentle skittering radiates from inside our walls. I cringe every time I hear it. Out come the traps, deterrents, steel wool, and spray foam. Homeowners like do whatever they can to keep damage-causing vermin out of our homes.
We all well know the littler mammals – mice, rats, opossum, and even cottontail rabbits and raccoons –will attempt to hole up in or under our homes in order to stay out of the cold, but what about the big guys? You know: the bears?
First, the details: To us everyday folk, the term “hibernation” is often used in a general sense to imply an animal which passes the winter away in hiding. True hibernation, in scientific circles, means a complete biological shift: breathing slows so it’s nearly imperceptible, heart rate lowers to just a fraction of the normal rate, and the body makes an impressive drop in temperature. The arctic ground squirrel’s body temperature drops below freezing – as low as 26.8°F[i] — during its hibernation, the lowest recorded for any mammal! In the case of our state’s beloved black bear, hibernation simply means eating lots to fatten up in order to lazily chill in your den until the cold weather passes. (Minus the hiding in our beds until April, for many of us humans the “eating lots to fatten up and stay warm” part sure sounds familiar around the November and December holidays.)
As the only bear species inhabiting our state, the American Black Bear is Minnesota’s largest hibernator (or pseudo-hibernator, if you prefer being exact) and the country’s smallest and most widely distributed bear species.[ii] According to MN DNR, black bears “are found mainly in the northern third of Minnesota, but range as far south as…agricultural zones, where they utilize corn and other crops for subsistence.”
Black bears are generally elusive and stay clear of humans, however during a late harvest November 26, 2019, a hibernating black bear that bedded down in a shallow den at the edge of a corn field was impaled by a combine near Boyceville, WI.[iii] As sad as it is, such a thing does happen where the local wild and agriculture meet. Our farms are excellent sources of food for man and animal, alike, after all, which is why maintaining awareness when working, hiking, scavenging, or harvesting in or near wilderness is so important: for our safety and the wild’s.
But what happens to all that good corn and other food the bears eat to fatten up for the winter sleep? Don’t they have to wake up during hibernation to… release it? Well, not really.
Bears’ bodies “accumulate feces in the lower 7-15 inches of the intestine to form a “plug” 1½ to 2½ inches in diameter. The fecal plug is simply feces that have remained in the intestine so long that the intestinal walls have absorbed the fluids out of it, leaving it dry and hard.”[iv] These fecal plugs – masses of dehydrated hair, fibrous plant material, cellular waste, and other unknown material – are basically big dehydrated chunks of poop which, in effect, causes the bear to plug up (i.e. constipate) until it’s time to wake up and get active again. It’s an unappetizing yet effective solution to a problem our sleepy bear buddies face when holing up for the season.
All I can say is: Thank goodness humans don’t take their winter habits after bears!
Author’s Note & Word Fun: Other local wild animals that hibernate through Minnesota’s winters are bats, chipmunks, woodchucks, and ground squirrels. Most reptiles and amphibians (snakes, frog, turtles) go into “brumation” or a hibernation of cold-blooded animals where they have to rest in an environment that will keep them warm.[v]
[i] Gough, Zoe. “Arctic ground squirrels’ super cool slumber”, BBC, 18Feb2015. http://www.bbc.com/earth/story/20150218-arctic-ground-squirrels-supercool-slumber. Accessed: 07Jan2020.
[iii] Sullivan, Sue. “Enormous black bear skewered by combine”, Cannon Falls Beacon (e-edition). Date: Unknown.
[v] “Ask a Naturalist: Hibernation vs brumation vs estivation”, Discovery Place Nature, 13Jan2016. https://nature.discoveryplace.org/blog/ask-a-naturalist-hibernation-vs.-brumation-vs.-estivation.