There are certain people who can be easily identified by their voices. For instance, if you close your eyes and listen, you can undoubtedly tell when someone like James Earl Jones or Morgan Freeman are speaking–simply by the tone and timbre of the sounds they produce.
Now, a team of researchers from Syracuse University have found that the same is true of North Atlantic right whales, as they have managed to correctly distinguish between 13 different whales in an initial study by using a combination of different characteristics, including the fundamental and harmonic frequencies they produced and the length of their calls.
In a statement, the scientists explained their research could allow them to identify and to track individual right whales, which could make it easier to study this elusive endangered species. The team will present their findings at this week’s spring meeting of the Acoustical Society of America.
Upcall duration key to distinguishing between different creatures
North Atlantic right whales, which eat tiny zooplankton in the waters along the east coast of the US and Canada, produce approximately a half-dozen different types of calls, the researchers said. They focused their research on a vocalization known as the upcall, which has a duration of about one or two seconds and increases in frequency from about 100 Hz to 400 Hz.
This places is at the low-end of the frequencies audible to humans, they added. The upcall is one of the most commonly produced types among right whales of all ages and sexes, and is probably used to signal their presence to other members of their critically endangered species.
Jessica McCordic, a masters student in the biology department of the New York university, and Syracuse biology professor Susan Parks, studied more than 10 years worth of acoustic data that had been collected from sensors attached to whales in Cape Cod Bay in Massachusetts, the Bay of Fundy in Canada, and in the waters of the southeastern coast of the US.
Their analysis of the achieved calls revealed that the duration of the upcalls were one of the main ways in which the sounds of different individual whales proved unique, and that by studying that trait and other variables, including the rate of the fundamental frequency change, they were able to distinguish between the upcalls of 13 individual right whales identified in the data.
“The analysis classified the whales well above chance levels,” McCordic said, “so that was really exciting.” She added that the next step is to see if this approach can distinguish between different right whales in the wild, using stationary hydrophones installed in their habitats. This technique could provide researchers with data that may help them protect the endangered creatures.