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 members. 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.

Kinship, association, and social complexity in bats

“…5b). Group stability is maintained by individual-specific vocalizations that are used to reunite individuals in a new roost every day (Chaverri et al 2010(Chaverri et al , 2013Gillam and Chaverri 2012;Chaverri and Gillam 2015). We did not detect any pattern between the strength of the relationship between association and relatedness and any feature of the social network.…”

The energetics of social signaling during roost location in Spix’s disc-winged bats

“…In moving groups, for example, members may produce social calls only sporadically (Deecke et al 2005), and individuals may become silent altogether when faced with increased levels of predation risk (Abbey-Lee et al 2016). The energetic costs of sound production may also explain why only some group members vocalize, as has been observed in bats where lactating females produce significantly fewer calls compared to non-reproductive and pregnant females (Chaverri and Gillam 2015). These intraspecific differences suggest that vocalizations involve higher energetic costs and that non-energetically limited individuals may be able to afford sound production for social communication.…”

Correlations between personality traits and roosting behaviours suggest a behavioural syndrome in little brown bats

“…Long-term recapture rates for free-ranging bats are typically low and, while repeatability of some social behaviours has been demonstrated over timescales ranging from a few days to several years (e.g., contact calls of free-ranging Thyroptera tricolor: Chaverri & Gillam, 2015), to date, repeatability of putative personality traits has only been quantified in bats on a short-term basis (i.e., 24 h: Menzies et al 2013). Quantifying behavioural variation for captive bats held in a semi-natural context could provide an opportunity to understand links between personality and social or roosting behaviours which may otherwise be extremely challenging to quantify for completely free-ranging animals in the wild.…”