Many mammals and birds are prone to antagonistic and hostile responses to contact with other groups outside of their community. But it’s not always like that. Bonobos, one of man’s closest living relatives, are an exception. But it’s not just terrestrial species that are outside the norm. Research recently published in the Royal Society Open Science shows a partial merger of two populations of Atlantic spotted dolphins (Stenella frontalis). Part of one northern community migrated 100 miles (160 km) to another in the south. Among the immigrants were dolphins of all ages and both sexes. The friendly contacts between the dolphins indicate that they were building social relationships.
Nicole Danaher-García, biologist, member of the Dolphin Communication Project (DCP) and one of the authors of this study, emphasizes that the peculiarity of these results is that they stayed there after they migrated: “It is usually unknown that this is the case in terrestrial mammals occurs. Even bonobos sometimes get together and spend weeks or months together, but often they separate again. These dolphins are still mixing. Therefore, they appear to be tolerant of strangers.” Another interesting problem with this new association is that although DNA testing is required to confirm paternity of the new offspring, matings do occur between Northern males and Southern females has come.
This investigation began unexpectedly and without human intervention. The study project, of which Danaher-García is a part, has been analyzing the dolphin population in the southern Bahamas since 2001, this community being specifically located in Bimini. From its inception through 2012, no new adults were observed except for young individuals who began to form part of the adult list. The population was about 120 people. But in 2013 they suddenly observed a more or less large new group of adults of different ages and both sexes in this area. Then they started to follow them: in the first year they saw dolphins from the south mixed with dolphins from another community.
“The following year we saw them much more frequently and were able to confirm that they came from an area called White Sand Ridge in northern Bahamas,” he explains. The original social structure was already clear and although a change in relationships was to be expected, both communities merged and even formed new, sometimes strong, connections. The dolphin population at White Sand Ridge has been studied for about 30 years. In 2012 and after a variation in the number of spotted dolphins, the total rose to 85.
In all, nearly fifty individuals were sighted from White Sand Ridge in Bimini in the five years following this migration. Up until 2019 they continued to see northern dolphins but this activity stopped with the arrival of Covid. However, Danaher-García comments that there are people who have seen individuals from both groups. “Maybe some of them went back north, but there is a large group that stayed,” he concludes.
A Bimini-born sociable adult male dolphin (right) swims peacefully with an adult White Sand Ridge male dolphin (center). Dolphin Communication Project/Approved by The Bahamas Department of Marine Resources 2014
It’s not the only recent study showing the associative ability of dolphins and their possible resemblance to humans. Research published in PNAS shows that dolphins are the second species capable of weaving a larger network of alliances behind humans. The results of the study, which analyzed 121 male Indo-Pacific bottlenose dolphins (Tursiops aduncus) in Shark Bay, Australia between 2001 and 2006, show that both dolphins and humans form strategic alliances between unrelated individuals. Within this network, the average number of adult males each male was directly associated with was 22. Some were associated with as many as fifty males. In addition, the length of time men associate with women depends on their being well connected with third-order allies, ie, with other groups. Therefore, alliances between groups increase access to a contested resource, thereby increasing reproductive capacity.
About 40 different species of dolphins are counted, with great diversity among them and in many cases very little information about them. Even between individuals of the same species there are differences in behavior. María Victoria Hernández Lloreda, who belongs to the Department of Psychobiology and Methodology of Behavioral Sciences at the Complutense University of Madrid, explains that the diversity of social behavior can be due to the specific circumstances of each community: “The same groups can behave tolerantly towards some and aggressive towards others. It depends on the pressure, the social or economic situation.” [entendiéndose económica como los recursos disponibles]. A 2017 study published in Nature Ecology and Evolution concludes that social cognition in cetaceans (both cetaceans and dolphins) may have evolved to mediate the ability to learn a range of behavioral strategies in response to life’s challenges and apply.
“The fact that they are more tolerant could explain that they also have greater flexibility and social awareness,” explains Hernández Lloreda. These social awareness skills allow dolphins to adopt the behaviors of others, “learning from the group,” he explains. “It’s not about having a behavior that’s predetermined. Depending on what you learn, depending on what social environment you’re in, you’re going to behave differently,” he elaborates.
Jose Fco. Zamorano Abramson from the Center for Research in Social Complexity at the Universidad del Desarrollo, Santiago (Chile), points out: “How do you learn? How is it that the same species behaves differently? Maybe it’s because you can say they have a tradition, a behavior in this group. There we speak of these groups presenting cultural traditions. Some differences can be explained because they have learned it socially from their family or group members and the others do it in different ways because they have learned it that way in their community.”
you can follow MATTER on Facebook, Twitter and Instagram, or sign up here to receive our weekly newsletter.
Subscribe to continue reading