Single pups are born mostly from mid-March through early May, peak in April. Pup nurses 12-18 days, then immediately begins independent feeding; generally enters water before weaning. Adults mate mostly during first 3 weeks of May. Gestation lasts about 11 months, including about 2 months before implantation. Males sexually mature usually at 6-7 years, females at 3-8 years; few live longer than 25 years. Adult females breed annually, except perhaps when food resources are in short supply. May congregate during breeding.