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

Abstract

Long-term social aggregations are maintained by multiple mechanisms, including the use of acoustic signals, which may nonetheless entail significant energetic costs. To date, however, no studies have gauged whether there are significant energetic costs to social call production in bats, which heavily rely on acoustic communication for a diversity of social tasks. We measure energetic expenditure during acoustic signaling in Spix’s disc-winged bats (Thyroptera tricolor), a species that commonly uses contact calls to locate the ephemeral furled leaves that they use for roosting. To determine the cost of sound production, we measured oxygen consumption using intermittent-flow respirometry methods, with and without social signaling. Our results show that the emission of contact calls significantly increases oxygen consumption; vocal individuals spent, on average, 12.42 kJ more during social signaling trials than they spent during silent trials. Furthermore, production of contact calls during longer periods increased oxygen consumption for males but not for females. We also found that as resting metabolic rates increased in males, there was a decreasing probability that they would emit response calls. These results provide support to the “allocation model”, which predicts that only individuals with lower self-maintenance costs can afford to spend energy in additional activities. Our results provide a step forward in our understanding of how physiology modulates behavior, specifically how the costs of call production and resting metabolic rates may explain the differences in vocal behavior among individuals.Summary StatementSpix’s disc-winged bats constantly produce contact calls while searching for roosts, which we show significantly increases an individual’s metabolic rate.

Food-associated calls in disc-winged bats

“…Therefore, the production of "screech" calls in this species, while strongly associated with foraging activities, is not considered to be exclusively associated with a feeding context (Clay et al, 2012). In contrast, the evidence collected in our study, together with results of previous studies (Chaverri et al, 2018(Chaverri et al, , 2021Chaverri & Gillam, 2016;Chaves-Ramírez et al, 2023;Montero & Gillam, 2015), shows that food-associated calls in T. tricolor are emitted exclusively in a feeding context, and that calls prompt social recruitment. Future studies are needed to confirm that T.…”

“…This type of call has not been previously described in disc-winged bats (Chaverri et al, 2018(Chaverri et al, , 2021Chaverri & Gillam, 2016;Montero & Gillam, 2015), and is markedly different from calls emitted by this species in situations of distress (Chaves-Ramírez et al, 2023). We also observed that vocalizations prompted two responses in receivers which are typically associated with food-calling (Clay et al, 2012), namely increasing feeding-related behaviors and social recruitment.…”

Consistent individual positions within roosts in Spix’s disc-winged bats

“…Age is also associated with RHP, since adults typically dominate over juveniles or subadults (Holand et al, 2004; Lu et al, 2013; Roden et al, 2005). Therefore, in our study we predict that dominance over positions within the roost will be primarily assigned to females, which are larger than males (Chaverri et al, 2021), and adults. Since we have not assessed the costs and benefits of different positions within the roost, we cannot accurately predict which position will be dominated by individuals with potentially greater RHP.…”