Hibernation of the Thirteen-Lined Ground Squirrel Citellus Tridecemlineatus (Mitchill)

Controlled experiments performed on large numbers of ground squirrels showed that individuals starved or given very limited rations went into hibernation sooner and hibernated longer than those receiving an abundance of food. Moderately bright illumination with electric light did not affect the tendency to hibernate in any way. Confined air and precooling the animals nightly both aid in the production of hibernation. Castration does not influence hibernation except during the breeding season in the spring when castrated males hibernate more readily than normal males. The few spayed females used also hibernated more than the normal females in the spring. Obesity is favorable to hibernation.