Temperature regime in burrows of ground squirrels (Marmotinae) during winter hibernation

The temperature regime of hibernation has been studied in six ground squirrel species from 13 geographic populations living beyond the permafrost zone. It is shown that hibernation usually takes place at low above-zero temperatures and that the least deep burrows are found in the zone of subzero monthly temperatures. Populations have been found that inhabit areas where monthly temperatures during the hibernation period fall below zero in almost the whole range of depths at which nest chambers are located.