Narwhals live in some of the coldest waters of the world around the Arctic Circle. They travel in groups hunting fish, shrimp, and squid deep in the ocean. They using a kind of radar, called echolocation, to find their prey in the dark waters. The male's single, long horn has always made them a whale of interest. Historically, the horn was sold as that of a unicorn, keeping up the legend of the mythical beast. But whale experts have wondered what the function of the horn, which is really a modified tooth, could be. Recently, a researcher at Harvard School of Dental Medicine studying the horn made an interesting discovery. It contains millions of tiny nerve endings that act as sensors and are capable of sensing the temperature, density, and saltiness (salinity), among other things of the arctic waters in which they live. This ability may well have helped them survive their harsh environment. (http://www.wisegeek.com/what-is-the-function-of-narwhals-tooth.htm)
