Natural Isotope Abundances in Bowhead Whale (Balaena mysticetus) Baleen: Markers of Aging and Habitat Usage

Abstract

The annual migratory path of the western arctic population of bowhead whales (Balaena mysticetus) carries them from the winter ice edge in the western Bering Sea northward through the Bering Strait and Chukchi Sea, and through leads in the offshore pack ice to the easternmost Beaufort Sea, where they arrive in early summer. In September and October, the animals move westward along the Canadian and Alaskan coast, returning to the Bering Sea by winter (Figure 15.1). Feeding occurs along this route. The principal prey organisms are the abundant copepods, euphausiids, and other invertebrates in the water column (Wursig et al. 1985; Lowry and Frost 1984; Braham et al. 1980). To capture their prey, the whales have a feeding apparatus that consists of a row of about 300 keratinous plates which grow from each side of the upper jaw. The plates fray on the inside to produce a hairy mat and also erode from the distal tips so that only young whales would be expected to have most of their total growth of baleen present. During feeding, the animal lowers its jaw while swimming and filters large volumes of water, retaining the zooplankton prey for consumption.