Researchers have discovered a wild short-beaked dolphin capable of communicating with other species of harbor porpoises, providing an example of interspecies communication.
Firth of Clyde, a large saltwater bay on the west coast of Scotland, is home to thousands of harbor porpoises and a wild dolphin named Kylie. Researchers had not observed Kylie with other short-beaked dolphins (Delphinus delphis) for at least 14 years, but it is not alone. On clear days in Clyde, visitors at the pier can sometimes see Kylie swimming alongside harbor porpoises (Phocoena phocoena), which are two-thirds its size.
Harbor porpoises near Shetland, Scotland. (Photo: Nature Picture Library).
A new study published in the journal Bioacoustics shows that Kylie is much more attached to harbor porpoises than scientists had imagined. While the sounds of short-beaked dolphins include a variety of clicks, whistles, and buzzes, Kylie does not whistle. Instead, it “talks” more like harbor porpoises, which communicate through sequences of high-frequency clicks. The study suggests that Kylie may be attempting to communicate with harbor porpoises, providing an example of the rich interactions between marine mammals, according to behavioral expert Denise Herzing.
Many years ago, the only short-beaked dolphin in Clyde appeared at the mouth of Kyles of Bute, leading locals to name it Kylie. No one knows where the dolphin came from or why it is alone, according to David Nairn, founder and director of Clyde Porpoise, an organization dedicated to studying and protecting marine mammals.
Some dolphins live alone after being separated from their pods due to storms, human activities, or orphanhood. To learn more about Kylie’s relationship with harbor porpoises, Nairn borrowed an underwater recording device and towed it behind his sailboat, Saorsa. Nairn recorded sounds from multiple encounters between Kylie and harbor porpoises from 2016 to 2018.
Mel Cosentino, then a PhD student at the University of Strathclyde in Glasgow, analyzed thousands of click sounds in the form of ultrasound from the recordings. While short-beaked dolphins whistle almost constantly, harbor porpoises never do. Instead, they only use high-frequency clicks with narrowband high-frequency (NBHF), with 8-15 amplitude peaks at 130 kilohertz. To hear an NBHF click, researchers had to slow the recordings down by over 100 times.
From the recordings, Cosentino identified the standard low-frequency clicks of short-beaked dolphins. However, even when Kylie was alone, Cosentino still detected clicks with at least 8 amplitude peaks at 130 kilohertz, the frequency that harbor porpoises typically use to communicate with each other. In other words, Kylie communicates like a harbor porpoise. The research team also noted that it never whistles like short-beaked dolphins usually do.
Cosentino observed that the exchanges between Kylie and harbor porpoises had a rhythm similar to that of members of the same species. They took turns communicating and rarely spoke over each other. However, the research team is still unclear about how much meaningful information is contained in the sounds produced by Kylie.
