The emergence of unshared consensus decisions in bottlenose dolphins

TL;DR

This study documents unshared consensus decision-making in bottlenose dolphins, showing that certain individuals initiate activity shifts through specific signals, with differences observed between males and females in decision influence.

Contribution

It provides rare evidence of unshared consensus decisions in wild dolphins, highlighting sex-based differences in decision-making signals and their relation to individual knowledge.

Findings

Males perform side flops to initiate travel, indicating decision influence.

Females perform upside-down lobtails to terminate travel, but are less influential.

Knowledge about travel timing is high among females, reducing the impact of individual signals.

Abstract

Unshared consensus decision-making processes, in which one or a small number of individuals make the decision for the rest of a group, are rarely documented. However, this mechanism can be beneficial for all group members when one individual has greater knowledge about the benefits of the decision than other group members. Such decisions are reached during certain activity shifts within the population of bottlenose dolphins residing in Doubtful Sound, New Zealand. Behavioral signals are performed by one individual and seem to precipitate shifts in the behavior of the entire group: side flops are performed by males and initiate traveling bouts while upside-down lobtails are performed by females and terminate traveling bouts. However, these signals are not observed at all activity shifts. We find that while side flops were performed by males that have greater knowledge than other male group members, this was not the case for females performing upside-down lobtails. The reason for this could have been that a generally high knowledge about the optimal timing of travel terminations rendered it less important which individual female made the decision.