EFFECT OF WATER RESTRICTION ON TEMPERATURE REGULATION OF THE FRUIT-BAT ROUSETTUS-AEGYPTIACUS

1. The thermoregulatory responses of the fruit-bat, Rousettus aegyptia cus, the only fruit-bat out of 32 bat species in Israel, were studied over a wide range of ambient temperature during normal hydration and d uring water restriction.2. The thermoneutral zone of the normally-hydr ated fruit-bat ranged between 31-36-degrees-C. Oxygen consumption in t his range averaged 0.95 +/- 0.15 ml g-1 h-1. 3. Evaporative water loss and respiration frequency during normal hydration increased as power functions of ambient temperature and were significantly correlated (P < 0.02). The normally-hydrated, heat exposed fruit-bat effectively reg ulated its body temperature and dissipated the total metabolic heat pr oduction by evaporative cooling. 4. In bats fed on oven-dried apples ( water restriction), body mass decreased by 20.72 +/- 2.78%. Oxygen con sumption between 32-36-degrees-C increased significantly and body temp erature was relatively high. Evaporative water loss decreased signific antly, except at 36-degrees-C where evaporative water loss was not sig nificantly different from that during normal hydration, suggesting the preference for body temperature regulation at the cost of increased w ater loss. At this ambient temperature, dry thermal conductance increa sed significantly compared to normal hydration, facilitating non-evapo rative heat loss. 5. We conclude that the Israeli population of Rouset tus aegyptiacus is adapted to the relatively warm climate and can cope with a decreased water content in its exclusive fruit diet and effect ively regulate its body temperature and metabolic rate.