By: Kathleen M Stafford // University of Washington, USA. Kit M Kovacs and Christian Lydersen // Norwegian Polar Institute and Øystein Wiig // University of Oslo
The small size of the Barents Sea bowhead whale population, in combination with its very tight affiliation with heavy sea-ice cover, along with the challenges that arise due to the darkness of the Polar Night, leave us knowing little about the status or behaviour of the animals occupying this part of the bowhead whale’s range. But recent studies led by the Norwegian Polar Institute indicate that the population numbers in the 100s, rather than the 10s, and Passive Acoustic Monitoring (PAM) of this species, which sings as part of its mating behaviour, has led to the discovery of a “hot-spot” in the western Fram Strait during the winter breeding season.
Extreme song diversity
In-depth analyses of three years of PAM records from Fram Strait show that bowhead whales singing at this site produced 184 different song types over the study period.
Most of the songs were only present for periods of hours to days, although each year a few song types persisted throughout the winter; no song types were documented in two different winter periods. It is not currently known if individual males use a single song or multiple songs during a year, or indeed, whether they switch from day to day.
Other whale species, such as humpback whales, tend to use one highly stereotyped song, which is sung by the whole population at a given time, with all animals switching to a new one when a change occurs. The song diversity seen in our bowhead whale study is “bird-like” in its complexity. No other mammals on the planet are known to produce such elaborate and varied songs. Why the songs of bowheads in this region are so complex is a mystery. The next step to solving the mystery is to see if the extreme song complexity shown by bowhead whales in the Barents Sea is a unique feature of this population, or whether it is a normal trait for bowhead whales as a species.
Kathleen M Stafford // University of Washington, USA
Kit M Kovacs and Christian Lydersen // Norwegian Polar Institute
Øystein Wiig // University of Oslo