The role of social calls for species discrimination in three sympatrically living Carollia species

Nocturnal, fast moving animals such as bats may rely on vocalizations to communicate at a distance. Differences in social calls providing species information may ensure the long-term coexistence of closely related species living in sympatry. Showing a high similarity in morphology, and overlap in niche use, sympatric species of the genus Carollia represent an ideal model to investigate the role of social calls for species separation. We hypothesize that social calls across species differ more in reproduction-related contexts than in other situations. Here, we focus on vocalizations from dyadic interactions in which a bat lands on a conspecific. Social interactions and concomitant vocalizations of three independently kept groups consisting of five C. perspicillata, six C. sowelli and 14 C. castanea were recorded in a flight cage at Hitoy Cerere Biological Reserve, Costa Rica, for several weeks. Video recordings of individually banded bats were made with three cameras in infrared light, and synchronized with the output of an ultrasound recorder. A visual discrimination of the situation-specific sonagrams revealed that, based on time-frequency contours, the three species used shared, as well as unique, call elements. The number of different contours varied from one (C. sowelli) to three (C. perspicillata), and nine (C. castanea), respectively. In a first statistical analysis, the shared call element “down-sweep” differed in peak frequency between C. perspicillata and C. sowelli suggesting species specific differences. A multi-parametric analysis will show to what extent social call differences separate sympatric Carollia species.