A Lonely Dolphin Has Learnt To Talk To Porpoises

In the Firth of Clyde off the west coast of Scotland, there lives a lone dolphin. Nicknamed "Kylie" by local people, the dolphin has lived there alone for 17 years. He probably became separated from his group and has hung around ever since, mostly near a particular navigational buoy.

However, it seems he has made some unexpected friends. Since 2004 Kylie has been seen in the company of local harbour porpoises. Now Mel Cosentino of the University of Strathclyde in Glasgow and her colleagues have recorded the sounds he makes, and found that he has adapted his clicks to sound more like those of the porpoises.

The results have not yet been published in a peer-reviewed journal, but Cosentino has presented them at conferences.

It's a remarkable display of learning, although we already knew that dolphins and other cetaceans were highly intelligent and adaptable, so we should perhaps not be too surprised.

It's not yet clear if Kylie is making noises that the porpoises find at all meaningful, or if he is simply imitating the noises they make without understanding their significance. In effect Kylie has the same challenge we face with things like whale song: we have the technology to mimic the noises, but we do not understand what they "mean" or how they affect whales that hear them.

What is clear is that wild animals often interact in surprising ways with members of other species. Many of these interactions have clear benefits, like the cleaner fish that remove parasites from their neighbours: the big fish get rid of their parasites, the cleaner fish get an easy meal. Such behaviours make evolutionary sense.

But others are more bizarre. For example, male fur seals on one sub-Antarctic island have been repeatedly observed having sex with penguins - very much over the penguins' objections, it should be said. We might speculate that the seals are simply mistaking the penguins for female seals, but this seems unlikely because the penguins are so much smaller. Instead it may be that these are young seals who cannot yet acquire mates and are sexually frustrated.

Similarly, in 2017 researchers reported that a young male Japanese macaque repeatedly tried to mate with sika deer by leaping on their backs. There surely can't be any mistaken identity there. Female monkeys have also been observed mounting deer. The explanation might be sexual frustration, or perhaps the monkeys are practising mounting behaviours, using the deer as reluctant props.

Quite what this means in evolutionary terms is unclear. Possibly these behaviours are harmful, in that they waste the animals' time and ultimately reduce their chances of reproducing successfully. Or possibly they are useful ways to regulate their internal state and mood, improving their chances of long-term survival.

In Kylie's case, it's not clear if he could ever join up with other dolphins, even if a group entered the Firth of Clyde. He has been alone for so long, without other dolphins from whom to learn, that he might not know enough about dolphin behaviour to fit in. Or maybe his experience fitting in with the porpoises will turn out to have been useful, teaching him the adaptability he would need to make a new life with other dolphins. Only time will tell.