Repeatability in the contact calling system of Spix's disc-winged bat (Thyroptera tricolor)

Abstract

Spix's disc-winged bat (Thyroptera tricolor) forms cohesive groups despite using an extremely ephemeral roost, partly due to the use of two acoustic signals that help individuals locate roost sites and group embers. While the calls that aid in group cohesion are commonly used, some bats rarely or never produce them. Here, we examine whether the differences observed in the contact calling behaviour of T. tricolor are repeatable; that is, whether individual differences are consistent. We recorded contact calls of individuals in the field and rates and patterns of vocalization. To determine whether measured variables were consistent within individuals, we estimated repeatability (R), which compares within-individual to among-individual variance in behavioural traits. Our results show that repeatability for call variables was moderate but significant, and that repeatability was highest for the average number of calls produced (R=0.46–0.49). Our results demonstrate important individual differences in the contact calling behaviour of T. tricolor; we discuss how these could be the result of mechanisms such as frequency-dependent selection that favour groups composed of individuals with diverse vocal strategies. Future work should address whether changes in social environment, specifically group membership and social status, affect vocal behaviour.