The Narwhal's iconic tusk actually experiences a great deal of sensation.
These tusks can grow as long as nine feet; it is actually and "exaggerated front tooth, the BBC reported.
"It takes a tremendous amount of energy and devotion to get that thing to grow," Harvard University's Martin Nweeia told Wired. "To expend that much energy in such a harsh environment - there has to be a pretty compelling reason to do it."
Researchers have come up with a number of explanations over the years for what purpose the tusk serves.
"People have said it's everything from an ice pick to an acoustic probe, but this is the first time that someone has discovered sensory function and has the science to show it," Doctor Nweeia told the BBC.
Recently researchers have decided more conclusively that the tusks serve a sexual purpose because they are seen more often in males and often used in fights.
The research team collected narwhal tusks collected by Inuit hunters near the Baffin Island, Wired reported. They found the tusks were packed full of nerve pulp that is similar to what is found in human teeth, except these tusks do not have protective enamel. They also found "two genes expressed in sensory signaling pathways" were at a much higher concentration in the pulp than in the jaw muscle or tissue.
The tusk is believed to be sensitive to both chemical and temperature changes. The team found as the narwhal swam through different levels of water its heart rate changed.
"The narwhal is the only example documented where teeth are shown to have the ability to constantly sense environmental stimuli that would not necessarily be considered a threat," Nweeia told the BBC. "If you were looking for an ideal and fascinating tooth to study there's no question this would be it."
