Dolphins Form Rare Alliance Near Bimini, Scientists Say

Royal Society Open Science (2022). DOI: 10.1098/rsos.211963″ width=”800″ height=”530″/>

Map of the Bahamas in relation to southern Florida, USA, focusing on the Little Bahama Bank and the northern Great Bahama Bank. The yellow marker indicates the Bimini Islands which are approximately 80 km east of Miami (blue marker). The red marker indicates the approximate location known as the WSR on the Little Bahama Bank, approximately 100 miles (160 km) north of the northernmost edge of the Great Bahama Bank. Card credit: Google Earth. Credit: Royal Society Open Science (2022). DOI: 10.1098/rsos.211963

Dolphins are known to be good at maintaining relationships, but a new study suggests their social dispositions may extend beyond their own social circles.

In a rare alliance, FIU postdoctoral researcher Nicole Danaher-Garcia says two communities of Atlantic spotted dolphins around the Bahamas have actually merged and formed their own complex society. She calls the merger a partial one, as only a few dolphins from one group mix with the other, but even a partial merger isn’t something Danaher-Garcia and the team of researchers expected to see.

“We’ll see small groups, maybe a few younger males, depending on the species, that will move between areas,” Danaher-Garcia said. “But the coming together of two large groups is very unexpected.”

The fact that the dolphins from the two different groups actually swim together, exhibit bonding behavior and possibly even mate, probably means that the dolphins have adapted over time and are learning to be wary – at least for animals that look like them. Traditionally, dolphins form alliances to keep their group together for protection, as well as to repel other dolphins that might try to access a group’s female population for mating. But when Danaher-Garcia observed a well-known group of dolphins, she noticed something else. In fact, she noticed 10 other things: dolphins she hadn’t seen before in this group.

Originally separated by 100 miles and a channel, one group of these Atlantic spotted dolphins was known to frequent the waters off Bimini, while the other lived near White Sand Ridge. Danaher-Garcia is a member of the Dolphin Communication Project, a collaborative team of scientists who have been observing, studying and photographing the dolphins in these areas for more than two decades.

Danaher-Garcia was on the boat taking photos that day when she spotted the newcomers who appeared to be friends with the Bimini dolphins. The researchers later compared those photos with photos from other research trips in Bimini and other areas, including White Sand Ridge. Based on unique markings, they were able to match those dolphins and others with photos previously taken of the White Sand Ridge community. This sent Danaher-Garcia’s research in a new direction.

The research team spent five years collecting data, completing hundreds of surveys, before halting their fieldwork due to the COVID-19 pandemic. During that time, they observed mixed groups during each field season and no inter-group aggression, which is common among dolphins to protect their territory. Even more surprising, the mixed group of dolphins actually showed bonding behavior, indicating that they welcomed the outsiders.

What exactly drives this peaceful integration remains unknown to scientists. It is possible for the groups to spend more time together, out of sight, working together to repel predators at night that feed in deeper waters. Or it may be a natural adaptation related to changing environmental conditions. Danaher-Garcia says this evolution of social tolerance among these spotted dolphins deserves further investigation.

Perhaps more importantly, these dolphins have given researchers even more to think about in terms of conservation.

“The climate is changing and the suitable range for many species is shrinking. Groups will likely have to share the same space as habitat availability decreases,” Danaher-Garcia said. “An important conservation question is how these group mergers will affect the species. We can imagine that habitat loss will have adverse effects on population size, but will the mixing of social groups also endanger them?”

The research results were published this week in Royal Society Open Science.

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More information:
Nicole Danaher-Garcia et al, The partial merger of two dolphin societies, Royal Society Open Science (2022). DOI: 10.1098/rsos.211963

Provided by Florida International University

Quote: Dolphins form rare alliance near Bimini, scientists say (2022, Aug. 11) retrieved Sept. 23, 2022 from

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