In early summer animals gather food to feed their young. In fall the focus shifts to winter survival. Some animals store food to eat through winter, and others simply eat more to build up fat reserves for the leaner months. Beavers sink branches into the soft mud near the lodge where they will spend the winter. Chipmunks build burrows with complex tunnels leading to nest areas and food storage, which they fill in the summer and autumn.
Squirrels bury food.
Occasionally a squirrel will forget where it stashed nuts or cones and a tree will sprout from that spot in the spring. Bears, deer, and raccoons all build up their fat reserves to keep from starving when food is scarce. The big brown bat, a common sight over lakes in the summer, is known for hibernating in buildings, but will also use caves and mines. Amphibians brumate in existing holes created by roots or small mammals. Due to our mild winter weather many animals in the Pacific Northwest, such as squirrels and bears, do not technically hibernate, but become inactive in their dens or burrows, and sleep for extended lengths of time.