Photo credit: foilistpeter licensed under CC BY-NC 2.0
by Daniel Fink, MD, Chair, The Quiet Coalition
Bearded seals are a key species in the Alaskan Arctic. The males use loud mating calls to attract females. Even their quiet calls have been likened to a chainsaw, but they have to call loudly enough over their equally noisy brethren to be heard by the female bearded seals they are trying to attract.
As a recent report notes, “Bearded seals – or ugruk in the Inupiaq language – are highly valued by Alaska Native communities in the high Arctic. Since bearded seals are at the center of subsistence and cultural activities in Inupiaq communities, threats to them threaten the communities that rely on them.”
Unfortunately, industrial development in the Arctic is increasing ambient underwater noise levels.
Bearded seals, as with many animals including humans, increase their vocalization volume to overcome increased ambient noise levels. This was described more than a century ago by the French physiologist Etienne Lombard, and it is called the Lombard or “Cocktail Party” Effect. Studies have shown that this adaptation to environmental noise probably evolved 300 million years ago.
Researchers at Cornell University’s Center for Conservation Bioacoustics measured bearded seal mating calls over two years. The calls increased in volume, but not enough to compensate from increased ambient noise levels caused by commercial activity.
This portends poor mating outcomes if the female seals can’t hear their suitors when it’s mating season.
Fortunately, the Cornell researchers have identified an upper limit beyond which male bearded seals cannot increase the sound pressure level of their calls.
We hope this information will be used to guide acceptable noise levels in the Alaskan Arctic.
