External Ears in Chiroptera: Form-Function Relationships in an Ecological Context

Abstract

External ears in mammals direct and enhance perception of sound. In bats, where navigation and foraging are strongly contingent on reception of sound, we would expect correlations between bat external ear morphology and echolocation signal structure, acoustic and aerodynamic properties, and foraging strategies. Using Web search engines, we collected peer-reviewed literature on these relationships, with the aim of summarising the knowledge on these correlations and establishing general form-function patterns. The literature on the relationship echolocation-ear, and foraging strategy was scant (six and ten publications, respectively). Fifteen more examined the aerodynamic properties and 46 the acoustic properties. Because of the complexity of the subject, few attempts exist that examine ear properties (acoustic, aerodynamic, shape) at the same time for more than a few species. The number of species so far examined represents less than 15% of the total number of species of bats. Although the available information did not allow to propose general patterns of morphological response of external ears to the factors examined, our findings suggested that further analyses of the relationship form-function in bat ears should consider the study of ears as integrated, multivariate morphological entities in which shape, aerodynamic characteristics, and acoustic properties, are an integrated, multivariate whole that ultimately contributes to the bat foraging behaviour.