Narwhals (Monodon monoceros), the so-called "unicorns of the sea" because of the males' single long tusks, are among the rarest whales on Earth. They're seldom seen, so their mating habits are largely unknown. When they are sighted, they are sometimes in large gregarious groups, or pods, of up to 20 individuals, though usually far fewer.
Though much of the reproductive and mating habits of narwhals remain a mystery -- chiefly because narwhals mate in pack ice offshore, where it is difficult to observe them -- some things are known. Males mature around 8 to 10 years old and females as early as 4 to 8 years. Mating takes place belly to belly, in the spring, usually between March and May. Females give birth to one calf around 14 to 15 months later, in early summer of the following year, and may not mate again for three years.
The long tusk of the narwhal is actually one of two teeth this species of toothed whales, (suborder Odontoceti, family Monodontidae) possesses. The left tooth of males, and in rare instances females, grows to great length -- usually between 6.5 and 8 feet. The tooth twists counterclockwise into a long, tapered spiral that grows through the whale's upper lip. Over the years, people have speculated that the tooth serves to dig around in the ocean bottoms uncovering food; to spike an ice flow for napping, to spear fish, to break ice, as a sexual display or for fighting other males. However, there is no conclusive evidence of any of these things. Newer evidence by Harvard School of Dental Medicine researcher Martin Nweeia, DMD, DDS, demonstrates that the tooth -- through a complex network of nerves, or hydrodynamic sensor capabilities -- may provide detailed information about the salinity of the narwhal's environment and tell the creature where certain fish he regularly consumes may be found.
Tusk Use During Mating
Whether or not narwhals use their tusks for display or dueling during mating season is a subject of much speculation. Male narwhals have been observed “tusking” -- the name given to the behavior wherein males cross tusks -- but while some researches speculate that the behavior may be sexually motivated, others think it may be simply a friendly exchange or greeting, or even a way to clean the tusks by rubbing them across one another. However, the fact that a male's tusk grow more rapidly after sexual maturity and that females rarely have a tusk, lends some credence to the idea that the tusk plays a role in sexual behavior. Other evidence of sexual rivalry and fighting between males includes broken tusks and scars.
Mother and Baby
Dark gray calves are born tail-first in June or July and average around 5 feet long. They have very little blubber at birth but put on weight rapidly during the 20 months or so in which they nurse upon the fatty milk of their mothers. Calves stay close to their mothers for protection and assistance during the nearly two years the calves needs to become self-sufficient.