Signature Whistles Help Dolphins Identify One Another

Experts have long known that dolphins boast an impressive "language" and complex social circles. However, it has really remained unclear how exactly they could tell one another apart aside from physical features. Now, a new study has revealed that dolphins may associate specialized whistles with certain individuals, essentially giving one another names.

The study, recently published in the journal PLOS One, details how wild Indo-Pacific bottlenose dolphins off the coast of south Africa, and Namibia (Tursiops aduncus) and the common bottlenose dolphin (Tursiops truncatus), use a communication system based on distinctive whistles.

These signature whistles, as they're called, have been observed in captive dolphins before, in that the whistles are exchanged just like humans would exchange names when they first meet. However, this new study is one of the first to examine this phenomenon in the wild.

Using a hydrophone - a microphone used for underwater recording - Tess Gridley, of the University of Pretoria and the Namibian Dolphin Project and Sea Search, and colleagues collected over 79 hours of recordings of signature whistles, alongside identification photos of the dolphins who made them.

"We found that the number of different signature whistles recorded increased when group sizes were larger and when calves were present - something you might expect if signature whistles are used to address each other and help maintain contact between animals, particularly between mothers and calves," Gridley explained in a statement.

The researcher added that observing these behaviors in the wild will help scientists to build a better understanding of how human activity is affecting the dolphins, as wild dolphin population communication could be threatened by increased noise from human activity.

Gridley fears that noise from recent costal construction in particular may block the dolphins' signals, making it harder for them to communicate with one other.

She and her team are also hoping to look into whether these individually distinctive calls can be used to monitor how the dolphins use their habitats, which can likewise help researchers understand if human activity is being disruptive to dolphin wellbeing.