BEHAVIOR AND MUSCLE PERFORMANCE IN HETEROTHERMIC BATS

Body temperatures of winter-resident Korean bats typically range from 10 degrees to 40 degrees C between August and September and from 3 deg rees to 15 degrees C between January and April. To learn how behavior and the motor systems of heterothermic bats respond to this body-tempe rature variation, we examined whole-organ ism performance and the temp erature-dependence of contractile properties of flight muscle in Murin a leucogaster ognevi. In winter and midspring, the lowest limits of bo dy temperature were 8 degrees C for biting and crawling, 16 degrees C for visually observable shivering, 22 degrees C for wing flapping (wit hout powered flight), and 28 degrees C for aerial flight. In summer, t he lowest temperature limits changed little for biting and wing flappi ng, but the temperature limits increased about 3 degrees C for crawlin g, shivering, and flight. Maximum isometric tetanic tension of the iso lated biceps brachii muscle was almost insensitive to tissue temperatu res between 10 degrees and 40 degrees C, with an average temperature c oefficient of 1.02 in summer and of 0.96 in winter. Rate of tetanic te nsion production between 10 degrees and 40 degrees C and shortening ve locity and power between 15 degrees and 25 degrees C were temperature sensitive, with average temperature coefficients of 1.3-2.3. Seasonal differences in contractile properties within each temperature were not significant, except for maximum tetanic tension at 30 degrees-40 degr ees C. Thus, the motor system of the bats had functional capacity over the range of body temperature experienced in winter to summer. The te mperature-dependence of behavior was consistent with muscle physiology . The defensive behaviors, like biting and crawling, observed at 8 deg rees-12 degrees C body temperature could be exerted by using temperatu re-independent tetanic tension, whereas activities, such as flight, th at require power generation would be restricted to higher body tempera tures by temperature-sensitive rate properties. Some rate processes ap peared to be more temperature sensitive in summer than in winter.