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Several Zoo Animals Will Hibernate Soon

Brown bear Boris
Brown bear Boris fattens up for the long winter.

Posted October 2020

When the leaves have changed and fallen from the trees, and the weather turns colder, it means winter is around the corner, and several of the Zoo’s animals will begin hibernation.

The Zoo is home to a badger, Oscar, four grizzly bears, mom, Ronnie, and her three male offspring, Bozeman, Chinook and Brian. Brown bear Boris lives in a separate habitat, not too far from the grizzlies, rotating time in the habitat with Bozeman, who outgrew his family group. All five bears begin hibernation around mid-November and wake up in mid-April. Of all the North American bear species, only polar bear Snow Lilly does not hibernate.

In addition, the Zoo’s prairie dogs go into a semi-hibernation called torpor. Torpor is a state of decreased physiological activity in an animal, usually marked by a reduced body temperature and metabolic rate.

Torpor enables animals to survive periods of reduced food availability. Animals that undergo torpor include birds and some mammals, including many marsupial species, and rodent species like mice and chipmunks.

Fast Facts


  • Zookeepers start changing diets for the grizzlies and brown bear about Sept. 1, adding fish to their regular diet and all the extra calories the bears will need for added weight throughout the winter.
  • In preparation for hibernation, bears put on an additional 20% in body weight. There is a drop in the bears’ activity level and their metabolism changes.
  • In the summer, bears take part in their normal activity, in the next stage of hyperphagia, they start to fatten up, afterwards, in the fall, they transition to slowing down and then mostly sleeping while in winter hibernation.
  • Hibernation usually begins mid-November, and the animals usually wake up in early April.
  • During the spring, the bears may experience “walking hibernation,” as they come out of hibernation. Throughout the winter, bears may wake up at sporadic times during the hibernation period.

Prairie Dogs

  • Prairie dogThe Zoo currently has two male prairie dogs, Groucho and Harpo, and these small mammals go through the semi-hibernation process.
  • Zookeepers make sure the exhibit is bedded down for the animals, adding extra straw for them to have throughout the winter.
  • During torpor, the prairie dogs stay in their underground chambers they’ve constructed, each of which allow for various activities like sleeping, eating and excreting waste.


  • Badger OscarThe Zoo’s badger, Oscar, is 4 years old, and goes through hibernation.
  • Because the outdoor habitat isn’t designed to handle snow and ice, which could cause cave-ins, the keepers prepare a winter box for him in the back area of the habitat.
  • Keepers give Oscar straw for bedding, and once he comes off exhibit, he’ll stay in the back area for the entire winter. Keepers try not to disturb hibernating animals and check their areas about once per week.

Harbor Seals

  • The Zoo currently houses four seals: males Ringo, Milo and Bosco, and female Cossette.
  • Harbor seals remain active through the winter. Keepers adjust their diets year-round, allowing each seal to maintain a good and healthy weight.
  • Seals are active up until mid-November, fattening up for the winter.
  • Adult male Ringo’s summer weight is about 220 pounds. During preparation for winter, he’ll reach ~ 300 pounds. During this time, keepers will feed him 3 pounds of herring and 2 pounds of capelin three times daily to maintain his weight through winter.
  • As spring approaches, the herring will be switched out with capelin, which is less caloric, and then herring will be omitted entirely and changed to squid which is extremely low in calories.