Stereotyped, repetitive gunshot call patterns produced by the North Pacific right whale, Eubalaena japonica

Abstract

The Marine Mammal Laboratory has deployed long-term passive acoustic recorders along the 50 m and 70 m isobaths throughout the Bering Sea since 2007. Instruments recorded at either 4 kHz on a ~7-11% duty cycle, or 8 kHz on a 30-45% duty cycle. In addition, directional sonobuoys were deployed during field surveys to allow real-time monitoring for large whale presence. During the 2010 survey, a stereotyped, repetitive gunshot call pattern was acoustically detected on sonobuoys. This same call pattern was then detected on two different long-term moored recorders in two separate years. Since then, six different stereotyped, repetitive patterns have been documented, three of which have been analyzed. Preliminary results show that each pattern has a minimum of 30 iterations repeated over several hours. Furthermore, in several cases, these patterns are repeated throughout the season, in consecutive years, and in one instance, in non-consecutive years. While male North Atlantic right whales produce long gunshot bouts similar to the reproductive advertisement known in other species, right whales are not known to produce any type of repeated stereotyped pattern. This represents the first study to document stereotyped repetitive gunshot patterning in right whales. [Work funded by the Bureau of Ocean Energy Management.]