The black bears at Northwest Trek have gone down for their winter naps, also known as torpor. During torpor, a bear’s body temperature and respiratory and metabolic rates decrease to conserve energy. The bears can maintain this low energy sleeping state for days, weeks, or even months without having much activity outside their den, including eating and going to the bathroom.
Northwest Trek’s black bears, Benton and Fern, typically go into torpor from November until February or March.
“Benton and Fern do have periods of activity during the winter months, where they will eat, go to the bathroom, and collect more bedding to remake their winter ‘beds’,” said keeper Haley.
Can you keep them awake?
Scientists describe torpor as an involuntary state, meaning that bears naturally experience some level of sleepiness. At zoos in warmer climates, where seasons don’t drastically change, bears spend less time in torpor.
“We have four very different seasons at Northwest Trek,” said Haley. “We want to support the bears in what comes naturally to them. We ensure the bears have exceptionally quiet surroundings this time of year so they can sleep as long as they like.”
Haley says she and other keepers also feed the bears a seasonally appropriate diet leading up to torpor so they can acclimate to the change in seasons as they would in the wild.
Can you spot them?
Benton and Fern have two sleeping options at Northwest Trek. Behind the scenes, they each have human-made dens, where they are offered food daily (although they don’t always wake up for it). The dens have heated floors and giant straw beds to get cozy in.
The bears also have a hibernation den near the center of the public exhibit. Guests can try to see if they can spot either bear napping there. Benton and Fern put a lot of work into preparing that den for winter each year, using ferns, fir boughs, and grasses as bedding.
“The den is a hole, five-feet in diameter, with an opening just large enough to accommodate the bears’ body size,” said Haley. “The den is meant to be pretty snug, in order for them to keep heat inside.”
Once comfortably inside, the bears will pull down even more vegetation toward the opening to keep it warm and dry. The den only fits one bear, and Benton and Fern will only trade places a few times throughout the four or five months of torpor.
What about the grizzlies?
Grizzly bears Huckleberry and Hawthorne, now almost seven years old, are accustomed to sleeping in their human-made dens. The grizzlies have practiced making dens over the past few winter seasons, but heavy winter rain usually fills them with water. More recently, the grizzlies have worked hard to dig out a large den that has withstood rainstorms, and keepers are excited to see if they add bedding to it this year. Hawthorne and Huckleberry will always have the choice of using the den they made or their human-made dens with heated floors and dry, fluffy bedding.
They are already transitioning into the colder winter months.
“We’ve seen them digging a lot at the top of their habitat and sleeping in the afternoon,” said Haley.
You might even see them lounging on logs and basking in the sun on a clear winter day.