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

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

In a rare alliance, FIU post-doctoral researcher Nicole Danaher-Garcia says two communities of Atlantic spotted dolphins around the Bahamas have actually come together, forming their own complex society. She calls the merger partial, since only a few dolphins from one pod mingle with the other, but even a partial merger is not something Danaher-Garcia and the research team expected to see.

“We’ll see small groups, maybe a few younger males, depending on the species, moving between areas,” Danaher-Garcia said. “But for two big groups to come together, it’s very unexpected.”

The fact that dolphins from the two different groups actually swim together, exhibit bonding behaviors and possibly even mate probably means that the dolphins have adapted over time, learning to let their guard down, at least for the animals who look like them. Traditionally, dolphins form alliances to keep their pod together for protection, and also to ward off other dolphins that might try to gain access to a pod’s female population to mate. But when Danaher-Garcia was observing a familiar pod of dolphins, she noticed something different. In fact, she noticed 10 different things – dolphins that she had never seen before with this group.

Originally separated by 100 miles and a channel, one pod of these Atlantic spotted dolphins were known to frequent the waters near Bimini while the other resided near White Sand Ridge. Danaher-Garcia is a member of the Dolphin Communication Project, a collaborative team of scientists who have observed, studied and photographed dolphins in these areas for more than two decades.

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

The research team collected data for five years, completing hundreds of surveys, before halting their fieldwork due to the COVID-19 pandemic. During that time, they observed mixed groups throughout each field season and no intergroup aggression, which is common for dolphins to protect their territory. Even more surprisingly, the mixed pod of dolphins actually exhibited bonding behaviors indicating they were welcoming strangers.

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

Perhaps more importantly, these dolphins have given researchers even more thought on the conservation front.

“The climate is changing and suitable ranges for many species are 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 sizes, but will the mixing of social groups put them also in danger?

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

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