The male narwhal reaches sexual maturity at eight to nine years old, and the female narwhal reaches that stage of its life at four to seven years old.
Based on the data available the female narwhal is able to give to one calf once every three years. The narwhal gives birth after a 15-month gestation period.
The breeding time for a narwhal whale is in the spring, and it usually takes place in mid-April, with the calf being born in the July of the following year.
The narwhal tusk is thought to play a strong role in the mating activity of the whale. Narwhals have been seen with their tusks crossed. And the tusks have also been seen used as weapons when males battle over a female for the right to mate. Additionally the tusk is known to experience a growth-spurt at sexual maturity in males; this has been interpreted as suggesting that there is a possible breeding function tied into the narwhal tusk.