Local birth season exhibits high degree of geographic variation, lasts 1-2 months within a particular area. Births occur mainly in May-June in Gulf of Alaska, Nova Scotia, and Newfoundland; June-July farther north in western Atlantic; February-March in Baja California. Lactation lasts 2-6 weeks (average about 3-4 weeks), followed within a few days by ovulation and mating, then blastocyst implantaion 1.5-3 months later. Females continue to forage during lactation period. Young weaned in 2-6 weeks (usually about 4 weeks). Females sexually mature in 3-6 years, males in 3-7 years. Few live beyond 25 years.