Two types of dormancy:
Sleep during coldest portion of each year (winter sleep) ·
Sleep during hottest parts of each year (July and August)
Just prior to these states of suspension, each animal accumulates body fat and plugs it's nest with as much as three feet of earth before settling down to sleep. While hibernating, heartbeat and respiration rates are greatly reduced and the body temperature drops to nearly that of the burrow. Emergence occurs in late winter and early spring.
*Squirrels are not obligate hibernators. Hibernation and estivation occurs on an individual basis and is influenced by environmental factors and the nutritional state of the animal. Also note that hibernation during the winter is mostly relegated to adults who have been able to accumulate the necessary fat stores. The spring born juveniles don't usually have the fat reserves. They can still be seen foraging above-ground even during the cold season. Estivation is also most common in adult squirrels.
How Biology relates to control:
Controlling dormant squirrels is not effective because they aren't feeding and fumigants cannot get to them because of the plugged burrows. Control methods can be used to deal with animals that are not in the dormant state.