Dolphins whistle their own tunes. It was news to us too! Here’s another fascinating nugget from our friends at SANParks Times.
While there might be much in a name for people, for dolphins, they call each other by their whistles. Commonly referred to as signature whistles, bottlenose dolphins use these to maintain contact and to address each other.
Dr Tess Gridley, a post-doctoral fellow at the University of Pretoria’s Mammal Research Institute (MRI) has authored a number of publications on the acoustic communication of bottlenose dolphins, including those found most commonly along our shores in South Africa, the Indo-Pacific bottlenose dolphin (Tursiops aduncus) and the common bottlenose dolphin (Tursiops truncatus) in Namibia. She has found that both species use a communication system based on signature whistle production.
“The population we study in Walvis Bay is a small, isolated population of common bottlenose dolphins. There are around 100 animals in this population living along the central Namibian coastline. In the same way that the desert elephants or desert lions are small, locally adapted populations, the common bottlenose dolphins in Walvis Bay should be considered quite an important population and are locally threatened by coastal construction and marine tourism.”
While there are some physical differences between the two bottlenose dolphin species, they seem to speak the same language.
The Indo-Pacific bottlenose dolphin is considerably smaller in body size,” says Gridley, and explains that common bottlenose dolphins in Walvis bay can grow up to 3.8 meters in length, whereas the Indo-Pacific bottlenoses in South Africa are smaller, less than 2.6 meters. “Those in South Africa can also be found in much larger group sizes compared to the common bottlenose dolphins we research in Walvis Bay,” she says.
Yet, both species use signature whistles. “In general the whistles of these Indo-Pacific bottlenose dolphins are lower in frequency and shorter than their common bottlenose cousins, but the communication system is very similar.” They are both producing these signature whistles which are likely used to maintain contact and address each other.
Most dolphin species rely on a rich repertoire of sounds in their day to day lives. They use sound to find food and navigate (echolocation) as well as communicate with each other. Dolphins can learn new sounds and can quickly mimic novel sounds that they hear. Although fairly common among many bird species and humans, this ability, termed vocal production learning, makes them quite special amongst mammals.
The vast majority of global research on bottlenose dolphin acoustic communication has been conducted in captivity. These studies have shown that each animal learns its own individually distinctive whistle, the so-called signature whistle, in the first year of life and that they use the same whistle throughout life. Research on wild dolphins in Florida confirmed that these whistles communicate identity information and other studies in Scotland have shown that signature whistles are exchanged by groups of dolphins when they meet at sea and that signature whistles are used to address each other – somewhat like a name in human society.
The outcomes of the most recent research project provide an important stepping stone for future studies into how sounds are used and whether human activities are affecting the communication of our whale and dolphin populations.