Their "horn" is actually a tooth! It is suggested that they use it for detecting levels of salt in the water, or hunting by poking the prey to stunt it and swallow it whole.Females typically don't have the tusk, and sometimes narwhals can develop two of them! Their tusk is very sensitive, having u to 10 million nerve endings. Some studies suggest that it has to do something with males competing and attracting mates. They are also in the same family with belugas and are able to produce offspring!