Humpback whales increase the length of their songs during nearby airgun operations

Abstract

There is concern that noise from “airguns” used during oil and gas exploration may cause behavioral changes in marine mammals. One important behavior of some mysticete whales is the production of songs which are likely used as reproductive displays. Humpback whales have conspicuous songs but there are few studies on the impact of noise on their singing behavior. Here, we test the hypothesis that airgun noise causes individual humpback whales to reduce the duration of their songs. In a series of experiments off the east coast of Australia, we exposed migrating humpback whales to airguns. We tracked and recorded singing males when we towed airguns through the study area as well as when there were no vessels or airguns present. We also noted interactions between singers and nearby conspecifics. Humpbacks usually stop singing when they join with others, and so joining is both a predictor of song duration and a biologically relevant outcome. Contrary to expectations, whales that were already singing prior to airgun exposure produced significantly longer songs than unexposed singers. However, the small number of whales that started singing during airgun exposure produced significantly shorter songs.