The initiative to burrow is strong in bears. The cubs at the WSU Bear Research, Education, and Conservation Center are no different, having recently dug out a significant den in the exercise yard for the first time.
Grizzlies like the cubs naturally dig to create dens to prepare for hibernation. It’s a little early, but some bears in the wild will dig out a den months in advance of winter. It’s also possible the cubs are practicing. Nobody ever taught them to do dig, they just started and created this:
The burrow goes back nearly 12 feet, and two of the cubs can fit in the inner chamber. The entrance is just big enough for one of them to fit through, which is typical of bear dens. The smaller the opening, the quicker it gets covered by insulating snow and the less space for body heat to escape during hibernation.
Most of the work was done by our two male cubs, Adak and Dodge, over the course of a week. Grizzlies can dig out up to a ton of earth in less than a week.
This den is built into the side of a hill in the exercise yard, which is common in the wild. Using the side of a hill is more energy efficient, as the tunnel is more lateral than vertical. Since hot air rises, a lateral tunnel works better to keep in body heat during winter months.
This den is near the fence line, so it may have to be collapsed by Bear Center staff. But in the past, dens have been allowed to last until the bears enter hibernation in their runs. They are always taken down and the land returned to how it was before the digging.
In the wild, dens are rarely re-used, as they tend to collapse in the spring due to runoff from snow melting. So our bears take the removal of their dens in stride.