Narwhals use highly targeted beams of sound to scan their environment for threats and food. In fact, the so-called unicorns of the sea (for their iconic head tusks) may produce the most refined sonar of any living animal.
An international team of researchers set up 16 underwater microphones to eavesdrop on narwhal click vocalizations at 11 pack ice sites in Greenland’s Baffin Bay in 2013. The recordings show that narwhal clicks are extremely intense and directional. Narwhals can widen and narrow the beam of sound to find prey over long and short distances. It’s the most targeted sonar signal measured in a living species, the researchers report November 9 in PLOS ONE.
The sound beams are asymmetric, narrowing on top. That minimizes noise clutter from echoes bouncing off the sea surface or pack ice, the researchers say. Narwhals also scan vertically as they dive, which could help them find patches of open water where they can surface and breathe amid sea ice cover. All this means that narwhals employ sophisticated sonar.
The audio data could help researchers tell the difference between narwhal vocalizations and those of neighboring beluga whales. It also provides a baseline for assessing the potential impact of noise pollution from increases in shipping traffic made possible by sea ice loss.