Spitsbergen’s endangered bowhead whales sing through the polar night

Abstract

Bowhead whales Balaena mysticetus are long-lived cetaceans, uniquely adapted among the baleen whales to live year-round in the Arctic. All bowhead whale populations were greatly reduced by commercial whaling from the 1600s through the 1800s, with the largest, the Spitsber- gen population in the North Atlantic, depleted to the point of extinction. Recent sightings of bow- head whales west of Svalbard precipitated an effort to listen for their vocalizations via 2 re - corders deployed in 2008 on oceanographic moor- ings spaced 95 km apart at 78.8° N latitude in the Fram Strait. Year-round acoustic records were examined for the occurrence of bowhead whale sounds. Simple calls, call sequences, and complex songs were recorded. Repeated call sequences or bowhead whale songs were detected nearly every hour from early November 2008 through late April 2009 on the western Fram Strait recorder. More than 60 unique songs were recorded from October 2008 to April 2009. In contrast, simple calls and call sequences were the most common signals recorded on the central Fram Strait instrument. Peak levels of song production coincided with the period of lowest water temperature, dense ice con- centration, and almost complete darkness. Given the diversity, loudness, and period over which songs were recorded, western Fram Strait appears to be a wintering ground — and potentially a mat- ing area — for this Critically Endangered popula- tion of bowhead whales.