Dugong dugon

Abstract

-Study of 42 marked Thyroptera tricolor in Puntarenas Province, Costa Rica, revealed that the animals live in groups of six to seven individuals. The members of each group always roost together in a rolled leaf of a plant, usually of the genus Heliconia. Each roost is occupied for one day. Each group seems to occupy an exclusive roosting area that averages 3000 square meters. The disk-winged bat, Thyroptera tricolor Spix, is one of two species in the Neotropical family Thyropteridae. It occurs from southern Mexico through much of tropical South America. A second species, T. discifera, occurs in parts of Central and South America. These small, delicately built bats (average weight about 4 grams) have forwardly directed funnel-shaped ears and very small eyes like funnel-eared bats (family Natalidae) and smoky bats (family Furipteridae). Thyroptera differs from bats of these other two Neotropical families, however, in having well-developed suction disks located at the wrist and on the ventral surface of the hind foot. These disks, the anatomy and functioning of which have been studied in detail by Wimsatt and Villa (1970), allow the animal to attach itself to smooth surfaces, such as leaves or glass. So far disk-winged bats are known to roost only inside the rolled new leaves of members of the banana family (Musaceae) or related plants. Within the leaves the bats arrange themselves in a vertical row in a head-up posture, attaching themselves to the leaves by means of the suction disks. Our studies of these bats in lowland Costa Rica revealed that the number of suitable roosts in a given area on any given day is very limited. Thus it is possible to locate all the potential roosts and find the resident bats with a considerable degree of predictability. After capture the animals may be marked for future recognition, and relocated at will. Here we present the results of two weeks of study of these intriguing little bats in Puntarenas Province, Costa Rica. Our findings suggest that the bats are organized into roosting colonies, that the members of each colony remain together, rejoining even if separated, and that each colony occupies an exclusive roosting area. METHODS