Tagging young humpback whale calves: Methodology and diving behavior

Abstract

Despite the importance of young animals to the proliferation of a species, logistic hurdles often prevent the study of individuals' behavior and habitat requirements. This is particularly an issue in the case of cetaceans, which spend a large proportion of their time at depth. We conducted a study to describe the dive behavior of young humpback whale Megaptera novaeangliae calves on their breeding grounds in Hawaii, USA. We first implemented and evaluated strategies for approaching whale groups and deploying suction-cup tags (DTAGs), resulting in 3 successful attachments of DTAGs in the winter of 2011. The approach technique that was most successful while minimizing reactions from the whale groups was a passive drift approach. Tagged calves exhibited consistent dives to shallow depths when their groups were stationary, and some deeper dives that approached the ocean bottom, up to 78 m in one case. Mean dive durations ranged from 2.2 to 3.5 min, with calves spending 40% of their time within 3 m of the surface. This is the first study to collect tag data from baleen whale calves less than 6 mo in age and provides habitat use data important for management of this endangered species.