Air availability and expandable vocal tracts shape the duration of mammal calls

Abstract

The longest and shortest duration calls produced by any animal, spanning five orders of magnitude, are produced by whales. This is at odds with our understanding that the duration of an animal’s call is driven by its size. In fact, we intuitively assume that large animals, with large vocal tracts, make long duration sounds, whereas small animals make shorter sounds. We compare the duration of the shortest and longest calls in the repertoire across 174 mammal species and show the relationship between body mass and vocalization length breaks down for mammals. For mammals that call underwater, those with modified vocal tracts (e.g., air sacs, expandable trachea, etc.) that move air between expandable reservoirs produce longer calls than predicted for their size. Those mammals without modified vocal tracts that call underwater produce much shorter calls than expected. We explore here the different evolutionary pressures that shape vocal signaling.