The young are weaned at 6 or 7 months when they are 11 or 12 m in length. Weaned calves travel with their mothers to the winter feeding grounds. Females probably reach sexual maturity between 3 and 12 years old and will reproduce every 2 or 3 years thereafter. Behavior Fin whales are variably gregarious. The usual pod size is 6 or 7 individuals, but groups as large as 300 have been observed migrating together.
Fin whales are highly migratory.
The spring and early summer are spent in cold, high latitude feeding waters. In the fall populations return to low latitudes for the winter breeding season. Because of the alternation of seasons in the two hemispheres, northern and southern populations never meet in equatorial waters. They can reach depths of 230 m with ease and remain under for up to 15 minutes. Fin whales are known to leap completely out of the water.