Tent construction and use by Uroderma bilobatum in coconut palms (Cocos nucifera) in Costa Rica

Abstract

Tent construction and use, uniformity of tents, and frond selection were studied in a population of Uroderma bilobatum roosting in coconut palms (Cocos nucifera) in Parque Nacional Palo Verde, Guanacaste Province, northwestern Costa Rica during July 1988. Palm leaflets were cut at their midribs in a line converging distally with the frond midrib, and the leaflets collapsed downward to form a large enclosed tent. Tent height, number of leaflets cut, and angle between the line of cut leaflets and the midrib of the fronds were measured to assess uniformity of tent construction. To ascertain if bats were selecting specific trees or fronds, we measured the angle of orientation of cut fronds, number of fronds hanging above a tent, and tree height. Bat tents were found in palms with a narrower range of heights than the overall tree population, and trees with tents were taller on average than trees without tents. A single altered frond provides excellent protection from rainfall. Bats do not seem to prefer fronds based on number of overhanging fronds or angle of orientation. The age of the modified frond may be an important factor in roost site selection, as tents in younger fronds were more likely to be occupied that those in older fronds. The number of bats roosting under tents ranged from 1 to 15 adults and subadults. The colony was composed largely of adult females and two age classes of young.