Bottlenose dolphins found in South Africa use signature whistles to address each other, said a new study by the University of Pretoria and the Namibian Dolphin Project and Sea Search.

According to the research by both institutions, both the Indo-Pacific bottlenose dolphin (Tursiops aduncus) and the common bottlenose dolphin (Tursiops truncatus) use a communication system based on their own individually distinctive whistles.

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Dr. Tess Gridley, project leader of the study, said researchers observed an isolated population of common bottlenose dolphins, one of the best studied dolphin species worldwide, in Walvis Bay.

Dr. Gridley and her colleagues gathered over 79 hours of recordings of signature whistles using a hydrophone (a microphone for underwater recording) and took photos of the dolphins that made them, The Daily Mail reported.

"The team discovered 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," Dr. Gridley said.

The lead researcher, however, was concerned for the long-term welfare of the dolphins and their capacity to cope with stressors or man-made pressures. These stressors include coastal construction, shipping and marine tourism that could interfere with the animals' communication.

"The common bottlenose dolphins found along Namibia's coastline should be considered quite an important population and are locally threatened by coastal construction and marine tourism," Dr. Gridley explained.

Reports said the study is an important stepping stone into how dolphins use sounds and how human activity is affecting the dwindling dolphin population.

TagsDolphins, bottlenose dolphins, animal communication, dolphins' signature whistle