A study shows that dolphins are able to recognise each other by the taste of their urine.
Researchers at the University of St Andrews have discovered that the mammals can recognise friends and family members without seeing or hearing them.
This unique sense of taste allows dolphins to tell their peers through their urine and other excretions.
In order to find out, Prof Vincent Janik, director of the Scottish Oceans Institute, and his colleagues Jason Bruck and Sam Walmsley, tested how dolphins responded to urine samples from different individuals.
According to the study published in the journal Science Advances, the sea creatures were more interested in urine from animals they recognised than ones they didn't know.
Janik, the lead author, said that dolphins explored urine samples for longer if they came from known animals or when they were presented together with the dolphin's unique signature whistle, an acoustic identifier that works like a name. The dolphins in the study were from the Dolphin Quest resorts in Hawaii and Bermuda, where their day job is swimming with tourists.
They live in natural seawater in their social groups and were ideal to study. By training animals to give urine samples when needed, the scientists were able to create a collection that was used across facilities to present known and novel tastes to dolphins.
The researchers believe that dolphins have a different experience of taste than other mammals due to this finding.
Janik said that we still don't know much about how the sense of taste works in dolphins. Other studies have shown that they have lost a lot of the common tastes that we find in other mammals such as sour, sweet, umami or bitter. They have unusual sensory cells on their tongue that are probably involved in this detection of individual tastes of other animals.