Male dolphins in Shark Bay establish sophisticated social groups in which they form long-term ties in order to cooperate with other males. They create smaller, less stable groups of two to three within huge, stable alliances to mate with females. Males that were stronger or more experienced were more likely to sire offspring in most species. The worldwide research team wanted to know if dolphins’ complicated reproductive social lives affected their reproductive success.
Whistle exchanges help allied male bottlenose dolphins retain weaker but crucial social bonds, according to researchers at the University of Bristol. While male dolphins are known to use physical touch, such as light petting, to connect with deeply linked allies, new research published today in Current Biology shows that they rely on less time-consuming voice exchanges to stay connected with weaker allies.
The researchers examined nine years of acoustic and behavioral data from a dolphin population in Shark Bay, Western Australia, along with colleagues from an international consortium of universities, to assess how male dolphins reinforced and maintained their valued partnerships.
Emma Chereskin, lead author from Bristol’s School of Biological Sciences, stated: “Tactile contact, or touch, is used by many species, including humans, to strengthen and reaffirm essential interactions. However, as the number of close social relationships grows, so do the demands on the time and space available for physical relationship maintenance. We wanted to investigate how male bottlenose dolphins maintained various alliance relationships in huge groupings since they build strategic, multi-level coalitions.”
We discovered that firmly bonded allies engaged in more affiliative touch behavior, such as caressing and rubbing, while less bonded allies engaged in more whistle exchanges within the core dolphin coalitions. This demonstrates how vocal interactions can sustain these weaker but nonetheless important social bonds.
Dr. Stephanie King
The research team was able to discover the many ways that these males linked with each other by tracking groups of affiliated males and documenting their physical and audio behavior.
Dr. Stephanie King, a senior author from Bristol, stated: “We discovered that firmly bonded allies engaged in more affiliative touch behavior, such as caressing and rubbing, while less bonded allies engaged in more whistle exchanges within the core dolphin coalitions. This demonstrates how vocal interactions can sustain these weaker but nonetheless important social bonds.”
According to Robin Dunbar’s social bonding hypothesis, vocalizations and language evolved as a sort of ‘vocal grooming’ to substitute physical grooming as progressively huge group sizes placed impossible demands on the time available for physical contact behaviors. However, testing of this idea in nonhuman monkeys shows that vocal exchanges occur between more strongly linked individuals who groom more frequently and hence do not provide evidence for physical bonding replacement.
“Our findings provide additional evidence that vocal exchanges can serve a bonding role, but more crucially, and in line with the social bonding hypothesis, that vocal exchanges can work as a replacement for physical bonding, allowing allied male dolphins to ‘bond-at-a-distance,” Chereskin stated. This evidence for social bonds outside of the monkey lineage raises intriguing new concerns about the origins and evolution of language across taxa.”
They examined 30 years of behavioral data from 85 male dolphins as well as genetic data to determine paternity for over 400 dolphins, discovering that well-integrated “popular” males with deep relationships to many group members produced the most offspring. Their position among the smaller groupings of two to three, as well as their age disparity with the other alliance members, had no bearing.
According to the study, male dolphins’ reproductive success is controlled by their social relationships with other males rather than their strength or age. The more integrated male dolphins are inside their social network, the more offspring they produce, according to scientists.
But how can they maintain their popularity? According to another study, these dolphins use whistling to retain vital links among their enormous social groups. The vocal interactions serve as a substitute for physical bonding and take much less time, allowing allied male dolphins to ‘bond-at-a-distance.’
The research team was able to discover the many ways in which these males bonded with one another. While physical contact, such as gentle touching, has been shown to connect dolphins with strongly bonded allies, they discovered that dolphins also maintain weaker, but still crucial, social bonds by whistling.
“Within the core dolphin alliances, we discovered that firmly bonded allies engaged in more affiliative touch behavior, such as caressing and rubbing, while less bonded allies engaged in more whistle exchanges,” says principal author Dr. Stephanie King of the University of Bristol.
