The function of the single, spiraling tusk of the narwhal, a marine mammal that lives in the Arctic, has captured the imagination of mariners and marine biologists alike. Is it an ice pick? A mate attractor?
A paper published in The Anatomical Record indicates that it acts like a long, pointy antenna, picking up signals from the animal’s environment.
The tusk is actually an overgrown, twisted front tooth. When the researchers dipped the tusks of captured narwhals into waters of varying salinity, the whales’ heart rates changed: higher salinities resulted in a faster beat. “This is the first time that someone has discovered sensory function [for the tusk] and has the science to show it”.