First measurements of humpback whale song received sound levels recorded from a tagged calf

Abstract

There is increasing concern over the potential ecological effects from high levels of oceanographic anthropogenic noise on marine mammals. Current US NOAA regulations on received noise levels as well as the Draft Guidance for Assessing the Effect of Anthropogenic Sound on Marine Mammals are based on limited studies conducted on few species. For the regulations to be effective, it is important to first understand what whales hear and their received levels of natural sounds. This novel study presents the measurement of sound pressure levels of humpback whale song received at a humpback whale calf in the wintering area of Maui, Hawaii. This individual was tagged with an Acousonde acoustic and data recording tag and captured vocalizations from a singing male escort associated with the calf and its mother. Although differences in behavioral reaction to anthropogenic versus natural sounds have yet to be quantified, this represents the first known measurement of sound levels that a calf may be exposed to naturally from conspecifics. These levels can also be compared to calculated humpback song source levels. Despite its recovering population, the humpback whale is an endangered species and understanding their acoustic environment is important for continued regulation and protection.