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Why does a dolphin whistle and a dog bark? Drivers behind the evolution of acoustic behaviour in mammals
Background / Purpose: The factors driving the evolution of acoustic behaviour in mammals remain unresolved. Conflicting hypothesis, the size-frequency allometry hypothesis and acoustic adaptation hypothesis, predict that body size or alternatively the environment have driven the design of acoustic signals. The movement of mammals from land to sea has provided an ideal natural experiment to examine how body size and environment have influenced signal design. We incorporate acoustic data from 220 mammal species including 156 terrestrial and 64 marine species and found that marine mammals have higher frequency calls and hearing capabilities compared to terrestrial mammals of the equivalent body mass. This is likely due to the increased sound propagation efficiency in water. As anthropogenic noise increases in the marine environment we propose that models may have value to predict acoustic behaviour of elusive, difficult to study marine mammals. Main conclusion: A model using both environment and body mass best describes the driver of the evolution of acoustic signalling in mammals. Aquatic mammals have higher frequency vocalisation and hearing than terrestrial mammal species of equivalent body mass, and this is thought to be due to the propagation efficiency of the aquatic environment.