Energetics of tent roosting in bats: The case of Ectophylla alba and Uroderma bilobatum (Chiroptera: Phyllostomidae).

Abstract

Roost selection in mammals is an important selective pressure, and many animals find shelter in previously existing structures. Furthermore, the microclimate of roosts is a crucial element for bat survival, and modified leaves are used for roosting ("tents") by 22 species of bats. Our objective was to determine whether the inverted boat tents used by Ectophylla alba and pinnate tents used by Uroderma bilobatum provide energetic benefits. We measured the ambient temperature under modified and unmodified leaves (UMLs) of Heliconia imbricata and Cocos nucifera. We also measured temperature with (simulated bat presence) and without a heat source, and finally we measured bat energy expenditure at different temperatures. Our results show that when a heat source is present tents conserve heat better than a UML. The energy expenditure of E. alba and U. bilobatum increased up to 55% and 48%, respectively, with a decrease of temperature from 25°C to 20°C. We concluded that since the temperature at our study site drops below 25°C every night and remains that way until mid-morning, using a "tent" that maintains a temperature higher than ambient temperature, or close to 25°C degrees, provides an energetic advantage.