Exploring a Hidden Structure in New World Bats: The Pollex

Abstract

Bats have an extraordinary morphological diversity and most of the studies have focused on exploring ecomorphology of wings, ears, nostrils, tooth, and skull. However, structures like the pollex have not been assessed yet. Here, I describe pollex measurements of 97 Neotropical bat species, analyze variation among guilds, and explore correlations with wing morphology. Besides sanguinivores, frugivores that use cluttered habitats and employ gleaning strategy showed larger pollex, whereas aerial insectivores that use open spaces presented smaller pollex. I found a negative relationship between pollex size and hand-wing length, but a positive relationship between pollex size and wing width. Results suggest a potential importance of the pollex on resource exploitation, especially in guilds associated to handling objects such as large fruits. Conversely, the pollex may be useless in aerial insectivores that employ other structures like uropatagium or dactylopatagium for prey capture and manipulation. The pollex is related to wing morphology and habitat use given that species with larger pollex and wide wings obtain their resources in cluttered habitats, while species with shorter pollex and longer wings acquire their preys over open spaces. It is important to keep documenting natural history of bats by studying unexplored structures that unveil the functional importance of morphology in resource exploitation