With the arrival of cooler temperatures in October and the appearance of early snow known as “termination dust” in the mountains around the Anchorage bowl, zoo staff are beginning to batten down the hatches for the approaching winter season. Hoses are picked up, habitats are prepared, animals are growing thicker coats and the zoo’s black and brown bears…well, they are getting ready for a long nap.
While these two Alaskan bear species sleep winter away in dens in the wild due to food resources dwindling in winter, zoo bears are offered food year round. So why do they den up and sleep when their food supply is constant? It boils down to personal preference, we suppose.
As fall sets in and the days get shorter, Zayk the black bear starts to leave food in the bowl. The zookeepers make note of this in his feed logs and they continue to track his food intake day by day. As he gradually leaves more and more behind, zookeepers start to bring straw in his den inside the black bear building. He makes himself a big nest and, with the onset of winter snow and cold and short days, Zayk is not seen until late spring when temperatures warm and days become longer.
The same is true for the zoo’s brown bears Izzy, Oreo and the zoo’s oldest resident 37 year old Jake. While each bear has come to live at the zoo from various regions around the state, they all three den up in the brown bear building dens. They follow the same progression as Zayk, with the main difference being an earlier waking period in the spring. While the brown bears are often seen roaming about sleepily on warm March days, Zayk is not usually spotted until April.
There is much known about how brown and black bears spend winters in their dens, while scientists are always researching to learn more. In this “Ask a Wildlife Biologist” article by Sean Farley of Alaska Department of Fish and Game, Sean discusses how bears spend their time in dens. Their body temperature goes down 8 to 12 degrees, they do not eat, they rarely urinate or defecate, they move around some to shift positions and they do sometimes emerge from dens when disturbed.
While we miss seeing Zayk, Jake, Oreo and Izzy all winter, we are glad they feel at home at the zoo and choose to live their lives in a natural way. We always look forward to seeing them in the spring and they emerge looking groggy, well-rested and healthy. And for all of the bear enthusiasts out there who plan to visit the zoo, have no fear. Polar bears do not sleep during winter months unless they are pregnant females as their food resources in the wild (seals) are more accessible to them when sea ice is formed. So our zoo polar bears do not have this biological clock ticking for winter sleep. You will see them up and around throughout the year!
To learn more about hibernation, check out this article by Alaska Department of Fish and Game.