Social Call Diversity in the Common Vampire Bat: Effects of Food Presence on Vocal Communication

Abstract

In many group-living species, vocal communication plays a critical role in coordination and cooperation. Common vampire bats are an emerging model system for studying how cooperative relationships form, yet the role of vocal communication in coordinating social interactions such as cooperation and social foraging remain unclear. In this species, only one social call type, the “contact call”, has been studied in detail. The goals of my thesis were (1) to more fully explore the vocal repertoire of the common vampire bat, and (2) to test the hypothesis that “up-down calls” are associated with food. I recorded a captive colony of vampire bats using ultrasonic microphones for seven 24-hour recording periods. To detect and classify social calls into types, I trained an image-based deep learning model to manually label spectrograms, distinguishing them from echolocation calls and background noise. To quantify the diversity of social calls, I also inspected spectrograms and used clustering via Uniform Manifold Approximation and Projection (UMAP). This analysis revealed that vampire bats have greater vocal diversity than previously recognized. Next, I used binomial generalized linear mixed-effect models to test whether the probability of recording either up-down calls or contact calls was higher when food was present in the cage. Clustering revealed multiple distinct call types, including a previously undescribed but common “wavy” call type. I found that, relative to other call types, up-down calls are proportionally more common in the presence of food. In contrast, the proportion of contact calls decreases when food is present. The presence of food therefore shifts the bats’ production of call types, providing new directions for investigating the role of vocal communication in vampire bat sociality.