Each October, responding to a silent start gun, pregnant females lead the way south. Their destination is one of several subtropical lagoons along the coast of Baja, where they will give birth. Mating takes place primarily during the southward migration, in late November and early December. Females impregnated during the migration will give birth to a single calf the following year, enroute to or upon arrival in the Mexican lagoons. March, the northward procession occurs in two waves.
Single whales are the first to leave.