Maintenance of the pectoralis muscle during hibernation in the big brown bat, Eptesicus fuscus

Abstract

The relationship between pectoralis muscle mass and body mass is examined throughout the annual body mass cycle in Eptesicus fuscus in order to evaluate muscle maintenance during hibernation. E. fuscus undergoes large fluctuations in body mass during the year due to pregnancy, parturition, prehibernation fattening, and hibernation (Table 1). Parallel changes occur in pectoralis muscle mass and total pectoralis protein mass (Table 2). The strong correlation between log pectoralis mass and log body mass (Fig. 3) and the lack of correlation between pectoralis mass and forearm length (Fig. 1, 2) suggest that the seasonal variation in pectoralis muscle mass represents a compensatory response to changing body mass. In active bats this relationship closely resembles the compensatory response predicted by flight theory.