Pandemic calm helps people eavesdrop on rare dolphins

The calm waters of the Gippsland Lakes near Melbourne, Australia are broken by a fin, and the calm afternoon is pierced by a tall pipe. A Burrunan dolphin broke the surface before diving and emitting the sound that would normally only be received by other aquatic animals. This time, however, the dolphin’s signal is being picked up by a team of scientists for whom the coronavirus pandemic had a silverback stripe.

In the past, her records of communicating with dolphins were obscured by the whirring, clinking, and splashing of boat traffic in this lake system that is just a few hours’ drive from a city of five million people. But lately there has been an unusual silence both above and below the water.

While Melbourne is still working its way out of a long, rigorous lockdown, human activity in this collection of pristine lakes, lagoons and estuaries that stretch for more than 60 kilometers along the Victorian coast and are partially separated from the Tasman Sea by sand is sharply receded dunes.

Reducing the noise has brought rare underwater silence to Marine Mammal Foundation (MMF) scientists and has provided an unusual opportunity to effectively record and interpret the language of endangered Burrunan dolphins for the first time. The founding director of this Australian non-profit organization, Kate Robb, was responsible for classifying the burrunan as a unique type of bottlenose in 2011. (A recent paper has denied that the burrunan is a distinct species in its own right, although Robb says it is “very widely accepted” as its own species among their peers.)

Previously there were only two known types of bottlenose worldwide – the common bottlenose and the smaller, lighter colored Indo-Pacific bottlenose. Robb analyzed genetic samples from some of the 185 Burrunan dolphins in the Gippsland Lakes and Port Phillip Bay that flank Melbourne and found that they did not match either of these two identified species.

MMF scientists have studied the Burrunans for more than a decade, but the pandemic silence has only just made it possible to understand what the aquatic mammals were saying through 3,000 hours of clearer recording of the animal’s noises. Robb says the footage shows that every burrunan has a “signature whistle” – a unique greeting for other dolphins, much like they say their own names. The recordings also begin to reveal complex relationships between members of the Pod, some of whom were close friends for up to 14 years.

Deciphering animal communication has long fascinated humans and dolphins. As one of the most intelligent creatures in the world, many such studies have been the focus. For a long time, a central aim of this work has been to finally identify the outline and complexity of dolphin communication and to determine whether it is a language that humans can understand.

Communication and language are of course two very different things. The former generally refers to conveying information, which can be as simple as an animal baring its teeth to convey aggression. In comparison, speech is communication using complex systems of symbols, words, or other signals.

Scientists have known for decades that dolphins emit sounds in sophisticated patterns. They emit high-pitched whistles to notify other dolphins, give burst pulse signals as they socialize, and emit clicks for echo localization.

Identifying the dolphin in a capsule at any point in time is key to deciphering their communication systems, according to Laela Sayigh of the Woods Hole Oceanographic Institution in Massachusetts, which is not involved in the Burrunan research. “Without knowing who the sender or the intended recipient is, it’s very difficult to interpret your communication signals in a fine-grained manner,” she says. “There are also challenges in classifying their sound types as there is no system that is shared by all researchers. Thanks to a long-term research program in Sarasota, Florida, we know a lot about custom-made whistles from dolphins. But we know very little about most of their other signals. ”