Bottlenose dolphins display their creativity within the first few months of life by creating a unique sound (or whistle) that they use to identify each other -- you could consider this a name. But how do these names differ from one another? Turns out, they vary in terms of frequency, pitch, volume, and length, and are largely influenced by the ocean environment and demographics of dolphin populations.
Scientists have studied the signature whistle of bottlenose dolphins (Tursiops truncatus) for over 50 years and over the decades, have made important progress in understanding how these whistles are used and why. But there was a gap in understanding the exact factors that influence the dolphin’s singular whistles. Now, this new study seems to shed some light on the issue.
Gabriela La Manna and her team at the University of Sassari in Italy studied dolphins in the Mediterranean Sea. They found that dolphins who live in areas with more seagrass, for example, have whistles with a higher pitch and shorter length – compared to dolphins who live in areas of the ocean where the seafloor is muddier.
“Even if the dolphin is among the most studied species of Cetacean, many aspects of their ecology and behavior are still unknown,” La Manna told MailOnline. “Given how quickly human activities are changing the oceans, it’s important to understand the environmental and socio-behavioral factors that allow animals to adapt to their environment.”
What's in a name
Back in 2013, researchers found that dolphins imitate each other’s signature whistle to re-establish contact. Meanwhile, in 2018, a study on dolphins found they retain “their names” (or whistles) into adulthood. More recently, another study last week found dolphins can identify themselves not only by whistles but also by tasting their urine, which may sound weird, but shows that dolphins have sophisticated social mechanisms and place a lot of emphasis on differentiating between individuals.
In this new study, La Manna and her team went through 188 hours of recorded acoustic data collected by research groups from 2006 to 2020. The sounds were recorded at six locations in the Mediterranean Sea. The researchers studied the sounds of dolphins from the west and east basins, as there’s genetic variation between them.
They extracted 168 individual whistles from the recordings and analyzed their acoustic features based on a set of factors: population demographics, genetics, the local ocean environment, and the location where the whistle was recorded. Ultimately, location partially affected whistle variability, while genetic differences had no strong influence.
Meanwhile, demographic features and environmental conditions appeared to strongly shape signature whistles. This aligns with the “acoustic adaptation hypothesis”, the researchers argued, which is a long-standing idea that animals adapt their vocalizations to their local conditions to enhance the purpose of their sounds.
However, Jason Bruck, assistant professor at Stephen F. Austin State University, and author of the recent study on dolphin urine, told NBC that there could still be aspects of dolphins we aren’t aware of. Anatomical differences between dolphins could explain the variation of signature whistle styles, and genetics could explain those differences, he added.
The study was published in the journal Scientific Reports.
