Dolphins have a unique way of recognizing each other – by tasting each other’s urine. A recent study conducted by researchers at Stephen F. Austin State University and the University of St. Andrews has revealed that dolphins can identify each other’s individual chemical signatures through the taste of their urine.
While dolphins do not have olfactory bulbs, they are able to recognize each other through the molecular lipids present in the urine. The dolphins also use signature whistles to identify each other, a type of acoustic call that they invent like names during the first year of life.
By using taste and signature whistles, dolphins compensate for their lack of sense of smell.
The researchers conducted experiments in Bermuda and Hawaii by presenting eight bottle-nosed dolphins with urine samples from other dolphins they were either familiar or unfamiliar with. Overall, the dolphins spent three times as long sampling urine from those they knew, which was a stronger indicator of recognition.
The study also showed that dolphins investigate the presentation area longer when the audio and urine samples matched, suggesting that urine and audio calls are used together for recognition. The gene CD36, which allows dolphins to identify lipids in urine, is also present in most humans and helps us know when we’ve had enough to eat.
Studying the gene in dolphins could improve our understanding of how it works in people.
Besides using taste and signature whistles to identify each other, dolphins use genital inspection as a way to socialize and learn each other’s chemical signatures. The new study might help future studies that investigate how commercial and industrial chemicals affect ‘urine cueing’ in dolphins.
“We might find that oil spills, chemical runoff and other human effects can impede the dolphins’ natural ability to chemically signal to one another,” said Dr. Jason Bruck, the author of the study. “This might prevent males from identifying reproductively capable females or diminish dolphins’ abilities to recognize individuals through honest signals.” The study has been published in the journal Science Advances.