Decoding the functional adaptation of animal echolocation: a global macroevolutionary analysis

Echolocating animals actively emit pulses of ultrasound and perceive acoustic reflections to determine the position of objects in dark, often three-dimensional spaces. Echolocation specificity thus depends on the properties of the calls emitted, such as frequency, duration, and call "shape", and how this ultrasound is modulated, reflected, received, and interpreted. Currently, however, there is no coherent synthesis explaining the functional adaptation of ultrasonic call design across echolocating species. To address this, here we provide the first comprehensive global macroevolutionary analysis of echolocator call design in relation to functional adaptations. From a systematic literature review, we identified 1,329 echolocating mammal and bird species, with a predominantly pan-tropical distribution, plus an additional 117 unconfirmed echolocators. To link echolocation call design to functional adaptations, we characterized calls based on 5,146 acoustic records from 2,838 terrestrial and aquatic study sites across 140 countries. From a comparative phylogenetic analysis, we established that echolocation calls were linked to (i) call frequency- and variation related parameters, which were associated with orientation function, and (ii) call type and duration, which mediated prey acquisition. Although echolocators produced highly species-specific calls, we found no support for any consistent effect of social system or sexual size dimorphism on echolocation call characteristics; however, morphological and phylogenetic constraints did substantially influence echolocation call designs at the global scale. This link between echolocation call design and function underscores how calls are adapted to overarching ecological niche conditions, explaining the conceptual macroevolutionary basis for the global distribution and adaptive radiation of echolocating species.