Radioglucose Metabolism by Richardson's Ground Squirrels in the Natural Environment

Abstract

Radioglucose metabolism in Richardson's ground squirrels was measured to study the relationship among the metabolic demands (maturation, pregnancy, and lactation) on different age and sex groups, subsequent prehibernatory fattening, and order of entrance into hibernation. The specific activity of 14C in muscle proteins and muscle lipids of juveniles decreased from June to August by factors of two and 13-18, respectively, and in August specific activity in these tissue fractions in juveniles and adults was similar. In the same period, specific activity of the label in adipose lipids of juveniles rose fourfold to a level similar to, but not surpassing, that in adults. The specific activity of 14C in different metabolites varied infrequently between sexes of the same age group, even though many of the yearling and adult females had been pregnant a few weeks earlier. It is concluded that prehibernatory fattening is not accelerated in any subgroup of the population to compensate for the earlier metabolic demands of maturation and rearing of young, and the order of immergence is a reflection of those demands.