In 2013, a group of 52 Atlantic spotted dolphins, driven to migrate by unknown forces, left their home on Little Bahama Bank in the northern Bahamas. They traveled 100 miles south to the island chain of Bimini, a destination already inhabited by a community of 120 Atlantic spotted dolphins.
When groups of social mammals meet, things can get tense. For example, conflicts between chimpanzee communities are known for their violence. adult male mammals, especiallyInterested in protecting the region and providing access to women.
But for Atlantic spotted dolphins of the Little Bahama Banks and Bimini, the mixing and mingling seem to have gone by instead of swimming, the scientists found.
Two teams of researchers recently published papers about the growing dolphin community. Unlike dolphins, their analyzes were not mixed, and offered independent confirmation that dolphins from different groups formed stronger bonds over a shorter time frame. The rare event provides new clues about how these brainy mammals organize their complex societies, and may help predict what might happen if climate change pushes populations closer together.
Dennis Herzing, a marine mammal behavioral biologist at the nonprofit Wild Dolphin Project, and his colleagues observed dolphins on the Little Bahama Bank for nearly 30 years and began tracking 52 dolphins as they left.
“We were curious how they were integrating,” she said. “It’s a kind of natural experiment.”
Another team, the Dolphin Communication Project, observed dolphins in Bimini for 20 years. “All of a sudden we were seeing so many adults that we didn’t know,” said Nicole Danaher-Garcia, a behavioral ecologist with the group. She was certainly referring to dolphins, not other dolphin researchers.
Danaher-Garcia noted that aquatic mammals often spend their entire lives forming close bonds within their home group. But in Bimini, they were forming new friendships with strangers in only a year.
Dr. Danaher-Garcia’s team tracked which dolphins spent time together from 2013 to 2018 and analyzed how different animals touched each other. “At times you may have seen them rub their pectoral fins against each other. They look like they are playing patty-cakes,” she said. Dolphins can rub their foreheads on their friend’s belly, which is even more so. Indicates a strong bond. “You should like them,” she said, “and if they’re allowing you to do that, they should trust you.” Such friendly gestures were common among men From different groups, the team reports this week in the journal Royal Society Open Science.
The team did not observe aggression between the newcomers and the original Bimini crew, the kind of conflict often seen in nature when mammal groups merge.
“It’s very unusual,” said Dr. Danaher-Garcia. Instead, his team observed the animals socializing, playing and becoming fearful in native group lines, behaving similarly to bonobos.
She said it is possible that “like bonobos, they use sexual behavior to reduce stress.” Sometimes this baby can look like a dolphin ball. “You can’t really tell who’s touching whom and what’s going on,” she said.
Like both bonobos and chimpanzees, dolphins live in fission-fusion societies where they form strong bonds between individuals but can break those bonds and form new ones. Such bonds between individuals in different groups are not seen in many mammals, said Diana Rees, a marine mammal scientist and cognitive psychologist at Hunter College, who was not part of any of the studies. To see such social resilience within groups that previously did not live together is “quite exciting,” Dr. Rees said.
Danaher-García’s team suspects Bimini’s geography, sufficient shallowness, as well as abundant access to deep water for pasture, makes for more sociable interactions because dolphins do not need to fight over space.
But that doesn’t mean it was all frictionless. Dr. Herzing’s group observed some aggressive behaviors, such as slapping dolphins or head-shattering, that are common when males fight over mating opportunities. his group Mapped the associations of the cetaceans from 2015 to 2020 and reported the results last week in the journal Marine Mammal Science. But the fighting that Dr. Herzing’s team observed is not unusual and may have occurred within the same group of dolphins.
Dr. Herzing’s group has not yet published their analysis of the types of touch that occur in the new mixed group. The team stayed on a boat for long periods of time during the summer, watching dolphins. In contrast, Dr. Danaher-Garcia’s project had a limited sample size that focused more on men as opposed to men and women, Dr. Herzing said, and may have missed some offensive encounters.
“They probably didn’t see the aggression, maybe because there was nothing to fight for,” she said.
There may also be a difference in what the two studies classify as aggression, Dr. Herzing and Dr. Danaher-Garcia noted.
More research is needed to determine whether mixed dolphin groups are engaging more through mating. Dr. Herzing’s team, the Wild Dolphin Project, is getting the scoop on this by collecting dolphin feces and analyzing the genetic material in them to reveal the dolphins’ parents.
Guido J., a behavioral ecologist at Flinders University. Parra, who was not involved in any of the studies, said there was value in researching these interactions. An understanding of social interactions can help reveal how animal groups may respond to environmental change and aid in conservation. Dr. Para said researchers still have much to learn about the ecological factors that drive groups, the role of individuals in shaping social structure, and the costs and benefits of banding together.
This would be important because different dolphin populations could be pushed closer together. For example, in Bangladesh, rising seas encroached on a land boundary and brought river dolphins into contact with another dolphin species in the ocean, Dr. Herzing said.
“We don’t know exactly how the species is going to fare” she said.