The intelligence of dolphins is no longer to be proven, but how much do they resemble us in their way of communicating and maintaining relationships? Much more than one might think… They can call their comrades when certain tasks require some form of collaboration: for example when it comes to defending and impressing females in heat in groups. A new study finds that they achieve this by learning the characteristic whistles of their closest allies (sometimes more than a dozen) and remembering those who have always cooperated with them in the past.
The results are amazing: dolphins do use the concept of team membership (a skill previously observed only in primates). Thus, they will help to reveal how these animals maintain such complex and close-knit societies.
” This is a revolutionary study Says Luke Rendell, behavioral ecologist at the University of St. Andrews, who was not involved in the research. The results were published in the journal Nature Communications. This work also provides further evidence for the idea that dolphins evolved to possess large brains, to be able to maintain their complex social environments.
Friends for life…
Previous studies have shown that male dolphins generally cooperate in pairs or trios, in what researchers call a “first-rate alliance”. These small groups work together to find and reunite fertile females.
Males also cooperate in second-rate alliances, which can number up to 14 dolphins and defend against rival groups that attempt to steal their female (s). Some second-order alliances join together into even larger third-order alliances, offering males in these groups an even greater chance of having allies nearby in the event of an attack from rivals.
Dolphins often change partners in their first-order alliances, but they retain allies in second-order groups for decades, according to long-term behavioral studies conducted in Shark Bay, Western Australia. These groups are considered to be the central unit of male society. ” Males stay together their entire lives, at least up to 40 years Says Stephanie King, behavioral biologist at the University of Bristol.
A unique whistle
But how do males keep track of all the members of these complex groups? Scientists claimed their hissing sounds were the key. Each dolphin learns a unique whistle from its mother, which it retains throughout its life. Dolphins recognize and remember other people’s whistles, just as we recognize other people’s names.
To further study how male dolphins use their whistles, King and his colleagues turned to a population of Indo-Pacific bottlenose dolphins (Tursiops aduncus) living in the remarkably clear waters of Shark Bay. The team has been following the animals with a set of underwater microphones since 2016, allowing them to identify which dolphin was making which whistle.
From 2018 to 2019, the researchers placed a speaker underwater and played the hissing males on other males in their various alliances. These males were between 28 and 40 years old, and had been in these groups all their lives. Meanwhile, scientists flew a drone over the water to film the dolphins’ reactions.
The researchers expected that males hearing the hissing sound of their first-order mates would respond most strongly. But when they looked at the videos, they found that the strongest responses came from the males of the Dolphin Second Order Alliance – that is, animals that have always cooperated with them to fend off abusers. (see video at the bottom of the article).
” It was so striking Says King, lead author of the study. ” In 90% of the experiments, dolphins who heard the whistles of second-rate alliance members would immediately and directly turn to the interlocutor. “. The results suggest that dolphins, like humans, have a ” social concept of belonging to a team, based on the previous cooperative investment of an individual, rather than on the quality of his friends », She explains.
This study “provides the missing link” between the signature whistles of male dolphins and their cooperative alliances, says Frants Jensen, behavioral ecologist at the Woods Hole Oceanographic Institution, who was not involved in the research. Jensen and other experts predict that the researchers’ high-tech approach will help scientists unravel other mysteries of cetacean communication.
In the video below, a male dolphin is heard calling out for his mates. Shortly after, they turn around and follow him: