Narwhals may be the closest thing we have to unicorns on the planet and they’re almost as elusive as their nickname's mythical namesake. Now, scientists have caught the buzzing, clicking, and callings of the “unicorn of the sea” on audio – and it's beautiful. The study has been published in the journal PLOS One.
The East Greenland narwhals are a slightly different species from their marginally more outgoing western cousins, who dwell in the icy waters of Canada and northwest Greenland. The 6,000 or so whales are particularly isolated from human activity, separated from the rest of the world by colossal ice sheets and icebergs the size of Big Ben. But climate change is changing all that.
"Wide-scale changes are taking place in the Arctic, with warmer temperatures leading to shrinking summer ice coverage," lead author Susanna Blackwell from Greeneridge Sciences said in a statement.
"More ice-free water means easier access for vessels and industrial operations, such as exploration for oil and gas. The inhospitable pack-ice environment that is narwhals' home for much of the year has for millennia kept them in relative isolation – even from biologists."
Previous studies have attempted to record narwhal sounds with underwater microphones but the technology is limited and the results less than ideal, which means very little is known about the acoustic behavior of the cetaceans – or their response to humanmade noises.
Blackwell and her team used acoustic sensors and GPS trackers to monitor the sounds and movements of six narwhals. In total, they captured 533 hours of audio, which they then analyzed to work out how exactly the animals' acoustic behavior changed over time and location.
They noticed three distinct categories of noise: click, buzz, and call. The first two were used as a form of echolocation to find and catch prey, which they do with their distinctive "horn", actually a spiralized tooth. (How they do this was only captured on film for the first time ever last year, you can watch it here.) These sounds tended to be produced at depths of 350 to 650 meters (1,148 to 2,133 feet) and it was through the tracking of clicks and buzzing that the researchers were able to pinpoint the location of a particularly popular dining area.
Calls – an eclectic amalgamation of whistles, clicks, and sonic pulses – on the other hand, were recorded at levels much closer to the surface. These noises, the researchers suspect, are a form of communication between animals.
Interestingly, the researchers noticed the narwhals went suspiciously silent for 23 hours or so immediately after tagging. The "unicorns of the sea" are extremely skittish creatures with a notoriously poor response to stress and this highlights the need to monitor for periods of days or longer.
The next step is to test their reactions to human-made sounds using an air gun, but with narwhals, slow and steady wins the race.
