Mating and parturition begin in late February in the Gulf of St. Lawrence and in early March at the Front off Labrador. Gestation lasts about 1 year, including 2.5-month delayed implantation period. Lactation lasts an average of 12 days. Young enter water when ice breaks up. One pup per year. Sexually mature as early as 3 years and no later than 7-8 years; matures earlier in deleted populations than in dense populations. Vast majority of adult females breed annually. Pupping areas cover 20 to 200 sq km, with seal densities of up to 2000/sq km (Reeves et al. 1992).