Separating overlapping echolocation: An updated method for estimating the number of echolocating animals in high background noise levels

Bottlenose dolphin communication during a role-specialized group foraging task

A division of labor with role specialization is defined as individuals specializing in a subtask during repetitions of a group task. While this behavior is ubiquitous among humans, there are only four candidates found among non-eusocial mammals: lions, mice, chimpanzees, and bottlenose dolphins. Bottlenose dolphins in the Cedar Keys, Florida, engage in role specialized "driver-barrier feeding", where a "driver" dolphin herds mullet towards "barrier" dolphins. Thus trapped, the mullet leap out of the water where the dolphins catch them in air. To investigate whether dolphins use acoustic cues or signals to coordinate this behavior, vocalizations were recorded before and during driver-barrier feeding. Results of fine-scale audio and video analysis during 81 events by 7 different driver individuals suggest that barrier animals coordinate movements during these events by cueing on the driver's echolocation. Analyses of dolphin whistle occurrence before driving events versus another foraging technique, which does not involve role specialization, revealed significantly higher whistle production immediately prior to driver-barrier events. Possible whistle functions include signaling motivation, recruiting individuals to participate, and/or behavioral coordination. While the use of cues and signals is common in humans completing role-specialized tasks, this is the first study to investigate the use of vocalizations in the coordination of a role-specialized behavior in a non-human mammal.