Anthropogenic noise impairs cooperation in bottlenose dolphins

Understanding the impact of human disturbance on wildlife populations is of societal importance,1 with anthropogenic noise known to impact a range of taxa, including mammals,2 birds,3 fish,4 and invertebrates.5 While animals are known to use acoustic and other behavioral mechanisms to compensate for increasing noise at the individual level, our understanding of how noise impacts social animals working together remains limited. Here, we investigated the effect of noise on coordination between two bottlenose dolphins perform-ing a cooperative task. We previously demonstrated that the dolphin dyad can use whistles to coordinate their behavior, working together with extreme precision.6 By equipping each dolphin with a sound-and -movement recording tag (DTAG-37) and exposing them to increasing levels of anthropogenic noise, we show that both dolphins nearly doubled their whistle durations and increased whistle amplitude in response to increasing noise. While these acoustic compensatory mechanisms are the same as those frequently used by wild cetaceans,8-13 they were insufficient to overcome the effect of noise on behavioral coordination. Indeed, cooperative task success decreased in the presence of noise, dropping from 85% dur-ing ambient noise control trials to 62.5% during the highest noise exposure. This is the first study to demon-strate in any non-human species that noise impairs communication between conspecifics performing a cooperative task. Cooperation facilitates vital functions across many taxa and our findings highlight the need to account for the impact of disturbance on functionally important group tasks in wild animal popula-tions.

Automated summary

Understanding the impact of human disturbance on wildlife populations is of societal importance. Noise pollution can affect communication and behavior in a variety of species. In this study, we investigated the effect of noise on cooperation between two dolphins performing a task. We found that increasing noise levels led to decreased coordination and success in the cooperative task. This study highlights the need to consider the impact of disturbance on group tasks in wild animal populations.