Singing humpback whales respond to wind noise, but not to vessel noise

Abstract

Animal communication systems evolved in the presence of noise generated by natural sources. Many species can increase the source levels of their sounds to maintain effective communication in elevated noise conditions, i.e. they have a Lombard response. Human activities generate additional noise in the environment creating further challenges for these animals. Male humpback whales are known to adjust the source levels of their songs in response to wind noise, which although variable is always present in the ocean. Our study investigated whether this Lombard response increases when singing males are exposed to additional noise generated by motor vessels. Humpback whale singers were recorded off eastern Australia using a fixed hydrophone array. The source levels of the songs produced while the singers were exposed to varying levels of wind noise and vessel noise were measured. Our results show that, even when vessel noise is dominant, singing males still adjust the source levels of their songs to compensate for the underlying wind noise, and do not further increase their source levels to compensate for the additional noise produced by the vessel. Understanding humpback whales' response to noise is important for developing mitigation policies for anthropogenic activities at sea.

Too loud: A singing humpback whale responds to ship noise

“…In addition, the noise considered was from a fishing boat rather than commercial shipping and was therefore lower in amplitude. Thus, the findings presented here are intermediate between those reported by Tsujii et al [7] and Girola et al [8] in the sense that this whale continued to sing in the presence of elevated shipping noise but did modify the song structure substantially. Whether a change in the source level of units also occurred (i.e., a Lombard effect) is the focus of an ongoing analysis.…”

“…Their findings revealed that whales reduced or stopped singing when a ship passed within 500-1200 m, or in some cases after it had passed. In contrast, Girola et al [8] reported that, although humpback whales changed the source level of singing in response to wind noise, they did not make changes in response to vessel noise. However, that study focused on the lack of a Lombard effect in relation to vessel noise and did not examine changes in song structure.…”

“…Combined, these findings suggest that humpback whale response to vessel engine noise is probably more nuanced than previously reported. In other words, the response of singing whales to engine noise can fall somewhere in between cessation of song [7] and no apparent change [8].…”

Dynamic visual noise has limited influence on the habitat selection and behavioural activity of crustaceans and cephalopods

“…For example, in the vicinity of torrent streams where fast-flowing water creates low-frequency noise, many anuran frog species increase their calling frequencies to prevent their calls from being masked by ambient noise (Goutte et al, 2018). Likewise, humpback whales (Megaptera novaeangliae) increase the levels of their social vocalisations in response to elevated wind-dependent ambient noise (Dunlop et al, 2014;Girola et al, 2023aGirola et al, , 2023b.…”