Long-Distance Signaling in Crocodylia

Long-distance signals such as bellows, roars, headslaps, and infrasound pulses are important components of crocodilian behavioral repertoire, yet there is little or no published information on signaling for many species. Here, original data augmented with a compilation of published and unpublished sources are presented for 24 species of crocodilians. Their analysis shows that crocodilians adapt their signal composition to habitat structure by choosing physically different components. Flexible multi-component composition might partially explain the extraordinary evolutionary longevity of crocodilian signaling. Comparative analysis provides novel evidence for solving the long-standing debate about the phylogeny of the genus Tomistoma, supporting its affinities with crocodiles rather than true gharials. It also suggests that the absence of species with adult male length of less than 120 cm among extant crocodilians might be caused by the necessity of producing infrasound as an honest signal of status.