A fascinating story from CBC Radio — based on a new study in the academic journal Science Advances, dolphins can recognize the sound of a whistle or the taste of urine — yes, taste — to spot their friends.

What started as a study of how dolphins use their signature whistles has uncovered another way the cetaceans communicate: their urine. 

“It’s like your dog sniffing a fire hydrant,” study co-author Jason Bruck told As It Happens guest host Robyn Bresnahan. 

Bruck, an assistant professor of biology at Stephen F. Austin State University in Texas, said the study first set out to examine whether dolphins used sound — their signature whistles and chirps — in a similar way humans use names. In order to do that, they needed to test the animals’ response to a different sensory system, “to show that the dolphins had what’s called a representational understanding of their calls,” he explained. 

Researchers studied how dolphins at the Dolphin Quest resorts in Hawaii and Bermuda reacted to urine samples from both their peers and unfamiliar animals.

“We would then measure how long the dolphin kept its mouth open, sampling that urine,” Bruck said. “And so they would sample for much longer [the urine of] individuals they knew versus individuals they didn’t know.”

The dolphins reacted to the signature whistles of the animals they knew in similar fashion: focusing on the more familiar sounds for a longer period of time.

What’s more, dolphins seemed to be able to connect the whistles with the urine samples. The animals would respond longer when the whistles from a familiar dolphin matched their urine sample.  

“That means that dolphins have a representational understanding of signature whistles, which is a big deal,” Bruck said. 

The researcher said that while the dolphins involved in this particular study are captive, the phenomenon of urine sampling came from observations of the animals in the wild. “As the dolphin would urinate or defecate, the other dolphins would swim with their mouths through the plume, shall we call it,” Bruck said. ”

Since the dolphins don’t have a sense of smell, Bruck says that this method of recognizing each other may have evolved to replace that sensory system.

Thanks to Dick Kooyman for contributing to this post.