Acoustic coordination by allied male dolphins in a cooperative context

Synchronous displays are hallmarks of many animal societies, ranging from
the pulsing flashes of fireflies, to military marching in humans. Such
displays are known to facilitate mate attraction or signal relationship
quality. Across many taxa, synchronous male displays appear to be driven
by competition, while synchronous displays in humans are thought to be
unique in that they serve a cooperative function. Indeed, it is well
established that human synchrony promotes cooperative endeavours and
increases success in joint action tasks. We examine another system in
which synchrony is tightly linked to cooperative behaviour. Male
bottlenose dolphins form long-lasting, multi-level, cooperative alliances
in which they engage in coordinated efforts to coerce single oestrus
females. Previous work has revealed the importance of motor synchrony in
dolphin alliance behaviour. Here, we demonstrate that allied dolphins will
also engage in acoustic coordination, whereby males will actively match
the production and tempo of their threat vocalisations when coercing
females, and in some cases synchronise threat vocalization onset. This
finding demonstrates that male dolphins are capable of acoustic
coordination in a cooperative context and, moreover, suggests that both
motor and acoustic coordination are features of coalitionary behaviour
that are not limited to humans.