Influence of Body Weight and Size on the Mode of Wintering in Hibernators of the Family Sciuridae in Northeastern Russia

Energy expenditures in the Siberian chipmunk (Tamias sibiricus jacutensis Ognev, 1935) and long-tailed ground squirrel Citellus undulates jacutensis Brandt, 1843 during hibernation were compared. Energy expenditures were assessed by analyzing changes in body weight and gas exchange rate. The animals were weighed either monthly throughout the winter (26 ground squirrels and 9 chipmunks) or continuously (four to six times a day) in five ground squirrels (395 h) and three chipmunks (696 h). At a constant ambient temperature, the body weight of animals in both species decreased almost linearly during the day. The decrease in the body weight of hibernating grounds squirrels and chipmunks over a single short hibernation cycle was also approximated by a linear function, irrespective of species, age, and sex.