Homology between and antiquity of stereotyped communicatory behaviors of crocodilians

Crocodilians communicate with each other using stereotyped acoustic and visual signals that convey reproductive, territorial, and other information. I mapped 14 such behavioral characters onto a phylogeny of seven crocodilian species to determine behavioral homologies, under the assumption that such behaviors are heritable. The results indicate that the following are ancestral behaviors for Alligatoridae + Crocodylidae and, therefore, were present by the Late Cretaceous: intraegg vocalization; juvenile distress calls; circling during courtship; head-emergent tail-arched posture; snout lifting; head slapping; inflated posture; narial geysering; bubbling; mutual snout-rubbing; and rubbing the snout on the dorsal surface of an intended mate. Ancestral (Late Cretaceous) courtship behaviors of the clade included circling, narial geysering, bubbling, mutual snout rubbing, and rubbing the snout on the dorsal surface of the intended mate. The headslap-roar is an ancestral advertisement display for the clade represented by Crocodylus acutus, Crocodylus moreletii, and Crocodylus intermedius and was present by the Pliocene. The behavior of many crocodilian species has been little studied, and it is possible that the picture presented here will change with the addition of data from more crocodilian species.