Delta wearing the sound and movement recording tag (DTAG). Dolphin Research Center, Florida, USA
Dolphins working collaboratively are less successful in the presence of sound generated by humans, a University of Bristol-led team of researchers have shown.
The findings, published today in Current Biology, imply that dolphins cannot minimise the impact of human-made noise, even by adjusting their own vocal behaviour.
Along with with international colleagues, the scientists equipped two trained and highly motivated bottlenose dolphins at the Dolphin Research Center in Florida, USA, with suction-cup attached tags, allowing them to record the dolphins' vocalisations while the dolphins participated in a cooperative task. During the task, the dolphins had to work together to both press their own under-water button within one second of each other, while exposed to increasingly louder levels of noise.
The dolphins produced louder and longer whistles to compensate for the increasing noise levels but were still less successful as the noise got louder.
Lead author Pernille Sørensen from Bristol's School of Biological Sciences said: "For years we have known that animals can attempt to compensate for increased noise in their environment by adjusting their vocal behaviour. Our work shows that these adjustments are not necessarily sufficient to overcome the negative impacts of noise on communication between animals working together."
Bristol's Dr Stephanie King, senior author, added: "It also shows us that dolphins can flexibly modify their vocalisations in an attempt to continue cooperating with their partner, revealing that this species is capable of actively coordinated collaboration."
Cooperation is common in animal societies and many species use sound that may help coordinate cooperative actions, but using sound also makes them susceptible to disturbance from human-made noise pollution.
"Working with our colleagues at the Dolphin Research Center in Florida, we had a unique opportunity to study the negative effects of noise on cooperative behaviour in a controlled setting, something that is almost impossible to do in the wild. Our findings clearly highlight the need to account for how noise affects group tasks in wild animals," Sørensen noted.
Dr King explained: "We show that human-made noise directly affects the success of animals working together. If noise makes groups of wild animals less efficient at performing cooperative actions, such as cooperative foraging, then this could have important negative consequences for individual health, and ultimately population health."
This study was funded by The Branco Weiss Fellowship – Society in Science and a postgraduate grant from Bristol's School of Biological Sciences.
Paper
'Anthropogenic noise impairs cooperation in bottlenose dolphins' Pernille M. Sørensen, Abigail Haddock, Emily Guarino, Kelly Jaakkola, Christina McMullen, Frants H. Jensen, Peter L. Tyack and Stephanie L. King in Current Biology.
