Mating occurs late fall to midwinter in the northeastern Atlantic. Gestation lasts about 17 months (IUCN 1991). Litter size is 1. Calf may be dependent for at least 2 years, closely associated with mother for much of juvenile period. Calving interval has been estimated at 3-8 years (higher estimates may be more typical). Sexually mature at 10-18 years. Females become reproductively senescent at 35-45 years. Estimated maximum age 80-90 years in females, 50-60 years in males.