Bats, narwhals, beluga whales, dolphins, and a small smattering of people use echolocation to see. They emit sonic clicks that return to the ears and are transcribed into mental pictures of the environment.
Narwhals are medium-sized whales, closely related to the beluga. Their most distinctive feature is a lengthy unicorn-like tusk extending from a protruding canine tooth. This tusk is an exquisite sensor: detecting temperature, pressure, salinity, and other environmental features.
Unlike other whales, narwhals spend all their secretive lives in extreme Arctic conditions, primarily in waters off Greenland and the eastern coast of Canada. Narwhals can live up to 50 years. The Arctic waters are a fertile hunting ground. But living in the bracing waters has its hazards.
Like all marine mammals, narwhals have to come up for air every 25 minutes or so. Some die from suffocation when the sea ice suddenly freezes over.
There is more darkness than light in the Arctic seas, especially when diving into the depths to hunt. Hence narwhals employ echolocation to see.
Narwhal echolocating clicks are produced by organs known as phonic lips, at a rate of up to 1,000 per second. These exit through a narwhal’s head, which works like a lens in bundling the clicks into a narrow beam. How that is physiologically possible is not known.
The echoes that bounce back are picked up by fatty pads in the narwhal’s lower jaw. As with bats, narwhals can narrow or widen their echolocating beams at will. Broad beams are used to focus in on prey at close range.