New call type produced by the North Pacific right whale, Eubalaena japonica

Abstract

The North Pacific right whale, (NPRW), is one of the most endangered baleen whales in the world and has been the focus of intensive population monitoring studies. In 2010 during transit through the Bering Sea right whale critical habitat (BSCH), near-24-h acoustic monitoring was conducted using DiFAR-capable sonobuoys. A new call pattern was detected during a focal follow of a NPRW, consisting of a series of pulses with a fundamental frequency at 110 Hz and peak energy at 640 Hz, ending in a 250–150 Hz downsweep. This call pattern was repeated multiple times and detected in the presence of gunshot and upsweep calls. Directional bearings to the call were a perfect match to those of the gunshot call. Although humpback whales were present, bearings to the humpback vocalizations were in the opposite direction (200 deg difference). The only other species detected visually or acoustically in the area were fin whales. This same pattern was detected in October and November on a 2009 long-term recorder in the BSCH, also in the presence of gunshot and upsweep calls. Because directional information from the sonobuoys during the focal follow exactly matched those from the gunshot call, we attribute this call pattern to the NPRW.