Dolphins recognize their friends by the taste of their urine

Dolphins recognize their friends by the taste of their urine

Dolphins can identify fellow dolphins they’ve encountered by the taste of their urine in addition to their whistle, according to a study published Wednesday in the journal Science Advances.

This work, conducted by examining the reactions of eight bottlenose dolphins (Tursiops truncatus) in captivity, sheds light on a question that scientists have long wondered, namely whether animals can classify members of their species as “friends” to humans.

“Locating others in the ocean is difficult, and hearing or smelling a familiar person via taste is an important indicator” to locate them, the authors of this study wrote.

Especially since urine has the advantage that it stays in the water for a long time, even after the animal has left.

Much like dogs sniff each other when they pass each other, it is common for dolphins to inspect other individuals’ genitals. This gives them a chance to taste each other’s urine.

To find out if dolphins recognize their fellow dolphins in this way, scientists first trained other dolphins to urinate voluntarily in response to food rewards. Samples were collected with syringes.

The researchers then compared the responses of the eight dolphins (two females and six males) when either water or urine was poured into their tanks. As a result, the animals spent twice as long analyzing urine as they did water.

In a second step, urine samples from known dolphins and those from unfamiliar dolphins were tested: the subjects then spent three times longer sampling known samples than unfamiliar ones.

Finally, the scientists added sound through speakers. Dolphins have the particularity that each has a unique whistle that they develop at a young age.

As the urine was poured out, whistles were played by the correct dolphin that provided the sample, or by a completely different and therefore mismatched dolphin.

When the whistle matched the person to whom the urine belonged, the dolphins stayed near the speakers longer, showing that this combination garnered more interest.

According to the authors, this study represents “the first case of identity perception based solely on taste in animals”.

They believe it’s also “likely that dolphins can deduce other information from urine, such as reproductive status.”