P2.155 Thursday, Jan. 5 No energetic benefit to group flight in the free-tailed bat Tadarida brasiliensis SAVAGE, E.H.*; ALLEN, L.C.; CHADWELL, B.A.; HRISTOV, N.I.; Winston-Salem State University, NC; Salem College, Winston-Salem, NC; Guilford College, Greensboro, NC; Winston-Salem State University; Center for Design Innovation, NC firstname.lastname@example.org
Striking examples of group behavior abound in nature – insects, fish, birds and mammals come together guided by individual rules to form impressive patterns of movement at the level of the group. Several explanations exist for why organisms group and behave collectively – energetic benefit, information transfer and predator defense among others. Members of the group balance the benefits against the costs of the group – limiting resources, competition for optimal position and increased visibility to predators. Bats are particularly good models for the study of group behavior but little is known about how and why they structure and maintain their aggregations. In this study we examined the group behavior of Brazilian free-tailed bats (Tadarida brasiliensis) and tested the hypothesis if free-tailed bats group to gain an energetic benefit. We recorded the emergence of free-tailed bats using an array of thermal cameras and reconstructed the three-dimensional position of individual bats in the group. In addition we measured the wing beat frequency of bats as a function of group size, ambient light conditions and relative position in the group. Our results indicate that there is no energetic benefit to being in the group, in fact it is costly for the bats to aggregate in such dense clusters. Furthermore, there are no relative positions in the flight formation that give an energetic advantage to its members. This suggests that other reasons, such as predator defense or information transfer, drive the group behavior of these fascinating bats.