North Atlantic right whales ( <i>Eubalaena glacialis</i> ) ignore ships but respond to alerting stimuli

TLDR

North Atlantic right whales, heavily hunted in the whaling era, have not recovered, largely due to anthropogenic mortality from ship strikes. The study aimed to assess risk factors for ship strikes by measuring right whale responses to passing ships and controlled sound exposures. Using a multi‑sensor acoustic tag, the authors recorded whale responses to passing ships and to controlled sound exposures of ship noise, conspecific social sounds, and an alert signal. Whales showed a strong surface‑swimming response to the alert signal, a mild reaction to conspecific social sounds, and no response to ship noise or approaching vessels, a behavior that may increase collision risk.

Abstract

North Atlantic right whales were extensively hunted during the whaling era and have not recovered. One of the primary factors inhibiting their recovery is anthropogenic mortality caused by ship strikes. To assess risk factors involved in ship strikes, we used a multi–sensor acoustic recording tag to measure the responses of whales to passing ships and experimentally tested their responses to controlled sound exposures, which included recordings of ship noise, the social sounds of conspecifics and a signal designed to alert the whales. The whales reacted strongly to the alert signal, they reacted mildly to the social sounds of conspecifics, but they showed no such responses to the sounds of approaching vessels as well as actual vessels. Whales responded to the alert by swimming strongly to the surface, a response likely to increase rather than decrease the risk of collision.