(CN) — Like humans, bottlenose dolphins know who their friends are, using identifying characteristics by using taste and sound. The similarities to humans end there, though, since dolphins use the taste of pee to find their friends.
Published in the journal of the American Association for the Advancement of Science, Jason Bruck, Vincent Janik and Sam Walmsley of the University of St. Andrews School of Biology in Scotland found dolphins can recognize familiar individuals through both the taste of their urine and their signature whistle. Bruck defined signature whistle as a sound that individual dolphins develops and keeps for life.
For the dolphins, necessity caused them to use their sense of taste.
“They have lost their sense of smell because their nose is their blowhole and they have to exchange a large volume of air in under 0.3 seconds when they come up to breathe, and therefore only have taste as a chemical sense," Bruck said. "They obviously echolocate and they communicate with whistles that they innovate and learn from each other.”
Technically, many other mammals use urine to identify other animals. According to Bruck, dogs sniff rear ends and mice can determine the relatedness of humans by scent alone. But dolphins so far are the only mammals found to use taste to identify social partners.
Bruck went on to explain that after the authors realized that dolphins used this method to find familiar individuals, they collected urine and whistle samples from one dolphin. Then, they played the signature whistle through a speaker and placed urine samples near the speaker. In some trials, the signature whistle and the urine sample would come from the same dolphin. For other trials, they would use different urine or signature whistle samples from different dolphins.
In their experiment, Bruck said the team found dolphins tended to stay by the speakers longer if the urine sample and the signature whistle came from the same dolphin friend. Bruck said the duration of their stay near the speaker was true “whether dolphins had a history of getting along or whether they didn’t."
Friends or not, the dolphins used both the scent of urine and the sound of the whistle to spot familiar beings.
However, environmental pollution may harm the dolphins’ method of finding familiar dolphins. Theoretically, dolphins in the wild can navigate the open ocean to find fellow dolphins by following urine trails. That method is contingent on the absence of overpowering substances.
“We may find that oil spills, the chemicals we use to disperse oil, chemical runoff and other human effects may impede dolphins’ natural ability to chemically signal to one another,” Bruck said. “This might prevent males from identifying reproductively capable females or diminish dolphins’ abilities to recognize individuals through honest signals.”
Bruck did note the experiment is not necessarily indicative of how all dolphins operated. After all, the dolphins used in the study were under human care, not in the wild.
“While we hypothesize that dolphins in the wild most likely do this behavior as well, we still have to systematically study that,” said Bruck.
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