Phonation behavior of cooperatively foraging spinner dolphins

Area of Science:

• Marine Biology
• Animal Behavior
• Bioacoustics

Background:

• Spinner dolphins exhibit complex cooperative foraging behaviors.
• Acoustic communication, particularly whistles, is hypothesized to maintain group coordination.
• Existing paradigms suggest echolocation and communication are separate functions in dolphins.

Purpose of the Study:

• To investigate the acoustic communication strategies used by foraging spinner dolphins.
• To determine the role of different sound types (whistles and clicks) in group coordination during prey herding.
• To challenge the established view of compartmentalized echolocation and communication in dolphins.

Main Methods:

• Field observations of spinner dolphin groups foraging at night.
• Use of a multibeam echosounder to monitor prey and dolphin locations.
• Acoustic recordings using an array of four hydrophones at varying depths to measure sound rates.

Main Results:

• Whistles were detected only when dolphins were not actively foraging or were surfacing.
• Click rates varied with depth and foraging stage, with highest rates during transitions between states.
• Low click rates were observed during active feeding, but these clicks were consistent with echolocation signals.

Conclusions:

• Spinner dolphins may use clicks for direct or indirect group movement coordination during foraging.
• This suggests clicks could serve a communicative role, contradicting the compartmentalization of echolocation and communication.
• The findings propose an alternative mechanism for acoustic coordination in foraging spinner dolphins.