New research shows that dolphins recognize their friends by their taste | National Geographic

We humans recognize our friends by different things, like their smile, their voice, or the way they walk. Biologists have known for several decades that dolphins make friends, and that they recognize mates through their unique whistling. Surprising recent research shows that bottlenose dolphins use their sense of taste to distinguish the urine of their friends from the urine of dolphins they do not know.

Research leader Jason Brook, a marine biologist at Stephen F. Austin University in Texas, had not initially intended to investigate whether bottlenose dolphins could recognize each other by their urine. He actually wanted to know if dolphins use their distinctive whistles like humans use their names. But for that he needed a second way for the dolphins to get to know each other.

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To see if dolphins associate a specific whistling sound with a specific dolphin, Brooke used a separate substance: urine. One researcher previously observed that wild dolphins deliberately swim through clouds of urine. Brock suspects they were doing this because he is providing them with information.

“It was a gamble,” says Brooke, who recently published an article about the research in the trade journal. science progress† “And to be honest, I wasn’t too confident that it would work.”

Through experiments with captive dolphins, the team found that the animals are more interested in the urine and whistles of their friends than other species. This indicates that they know who they came from, says Brooke.

The findings are also the first documented evidence that some animals recognize certain species using their sense of taste. In addition, they have shown that by being able to identify individuals by at least two things, dolphins have a complex sense of who their relatives and friends are – just like humans.

“I was shocked, really stunned,” Brooke says. “I had a big smile on my face. I said, ‘Oh my God, this works.'”

Enthusiastic participants

In 2016 and 2017, Brooke and colleagues observed several bottlenose dolphins in dolphins in Bermuda and Hawaii, which also have animal husbandry programs. At these Dolphin Quest sites, dolphins live in ponds filled with natural seawater, which is similar to the environment they live in in the wild.

The researchers first investigated whether dolphins could detect urine in seawater. Dolphins have lost their sense of smell during evolution, but their sense of taste has become more developed.

In spacious ponds in which dolphins temporarily separated from each other, scientists poured water with ice into the water, and then monitored the reaction of the animals. Curious dolphins exploring ice water were good candidates for the experiment. The team then had to investigate whether the animals reacted to the ice water differently than they did to urine, and whether they reacted to the urine of animals they knew differently from the unknown animals.

When the animals lived together for at least five years, the team knew they knew each other. The researchers always poured 20 milliliters of unknown and 20 milliliters of known dolphin urine into the aquarium, and determined the order in which they did it using heads or tails.

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Dolphins spent about three times longer examining the urine of familiar animals than did the urine of unfamiliar animals. Some nose bottle dolphins even examined known urine for more than twenty seconds. However, they did not pay much attention to the urine of animals they did not know, they finished it just as quickly as the ice water.

“The dolphins were very enthusiastic about the study,” Brooke says, adding that the animals receive no food as a reward. Dolphins usually find my experiences boring. We used behavior that is part of the dolphin world.

Dolphin predictions

The final study looked at whether dolphins collect signals from other dolphins, that is, whether there is a connection in their brain between a particular individual’s whistling and his urine.

Brooke has benefited from what behavioral ecologists do a Expected violation Where animals are exposed to something wrong and their reaction is considered. This can be compared to a situation where you see your best friend’s face as a human, but hear a different voice.

In this latest experiment, Brooke examined the responses of ten dolphins to different combinations of urine sound. Five of these animals also previously participated in other parts of the study.

Dolphins have shown little interest in mismatching whistles with urine. This might be a workable solution to a situation in the wild, where mammals are exposed to the whistling sounds of animals while sniffing other dolphins, he says.

But when the dolphin was presented with the correct combination of urine and whistle, the animal scanned the environment on average for ten seconds longer than the incorrect combination. Two animals even stayed close to them for more than forty seconds. This was compelling evidence for the team that animals can recognize their friends.

Taste of success

It is very difficult to prove a concept of something in the brain of an animal. Experiments like this, in which this is being attempted, are very interesting and useful, said Bruno Diaz-López, a biologist at the Spain-based Putlinos Dolphin Research Institute who was not involved in the study.

Lopez thinks similar studies should be done in the wild, too. “This is a good approach and a good first step in investigating the role that the sense of taste may play in the recognition of dolphins by certain people,” he adds.

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“It really gives us a better understanding of how dolphins monitor each other. We know this is very important for these animals,” said marine biologist Laila Sage of Woods Hole Oceanographic Institution in Massachusetts, who was not involved in the study.

“This raises new questions about what animals can infer from the effects of urine,” she says.

Brooke wants to do more research into the biological mechanisms that dolphins use to taste urine.

Urine lipids, which can be picked up by a physical “antenna” on the taste buds, seem like a promising possibility. He adds that this research is absolutely necessary, because the effect of human pollution on animals’ sense of taste is not known.

This article was originally published in English at nationalgeographic.com

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