Behavioral repeatability and choice performance in wild free-flying nectarivorous bats (Glossophaga commissarisi)

Abstract

Animal individuals show patterns of behavior that are stable within individuals but different among individuals. Such individual differences are potentially associated with differences in foraging efficiency and in fitness. Furthermore, behavioral responses may be correlated in specific suites of so-called behavioral syndromes that are consistent across different contexts and with time. Here, we present a field investigation on individual differences between wild, free-flying nectarivorous bats (Glossophaga commissarisi) in the foraging context. We further investigated how individual differences affect choice performance, and we examined their interdependence within hypothesized behavioral syndrome structures. Free-ranging bats were individually identified as they visited an array of 24 artificial flowers with nectar of high or low sugar concentration. We found that three behavioral measures of foraging behavior were individually stable over the two-month observation period. We investigated the link between individual behavioral measures and measures of choice performance using generalized linear mixed models. Individual measures of choice performance showed significant repeatability, and we found evidence that bats making more visits per bout tend to be slower in learning to avoid unprofitable flowers. We used a multi-response generalized linear mixed model to estimate between-individual correlations and compare hypothesized syndrome structures. There were no clear patterns of between-individual correlations among the behavioral measures in our study, despite the measures exhibiting significant repeatability. This may indicate that foraging behavior depends on multiple individual behavior dimensions that are not adequately described by simple models of behavioral syndromes.

Significance statement

Nectar-feeding bats, like other animals including humans, have their own peculiar ways of consuming food that differ among individuals of the same species. We characterized the feeding habits of individuals in a population of wild, free-flying bats that were trained to gather nectar from computer-automated artificial flowers in a Costa Rican rainforest. Individual bats responded to the experimental conditions in different ways, but consistently over the two-month observation period. For example, some bats frequently returned to the same flowers, while others tended to meticulously probe most flowers they encountered before returning to a previously visited location. Interestingly, bats also consistently differed in how fast they learned to avoid flowers with dilute nectar and the faster learners were the bats that made only a few visits on each feeding trip. This suggests that individual foraging strategies might be associated with differences in foraging efficiency.