Baby Seal

Life history
Reproduction
Males of some species, including Elephant seals, South American Sea Lions, and Northern Fur Seals) aggressively defend groups of specific females, referred to as harems. Males of other species, including most sea lions and Brown Fur Seals) defend territories on reproductive rookeries while females move freely between them. Occasionally violent competition for females or territories is an integral part of male breeding strategy among most pinnipeds. Otariids, which are generally more land-adapted, form major aggregations in the summer months on beaches or rocky outcrops. Consequently, their reproductive behavior is easier to observe and relatively well-studied. Walruses and many phocids, on the other hand, form smaller aggregations, often in remote locations or on ice, and copulate in the water. Their reproductive behavior is less well known.
Females have a postpartum oestrus that allows them to mate soon after giving birth. Delayed embryo implantation (embryonic diapause) obviates the need to come ashore (haul-out) twice, once to give birth and again to mate. After giving birth, mothers suckle their young for a variable period. Phocid lactation varies from 4 to 50 days, whereas otarids lactate from 4 to 36 months. This reflects the fact that phocid feeding grounds tend to be far off-shore, so lactation is associated with maternal fasting. To compensate for the short lactation period, the fat content of phocid milk (45–60% fat) is higher than in any other marine mammal species. After lactation, most females migrate to feeding grounds for intensive foraging to recoup energy reserves. Otariid feeding grounds are generally closer to shore and mothers take foraging trips. Otariid milk fat content is lower than that of phocids, owing to the protracted lactation period (typically 25–50%). Protracted nursing also leads to the formation of social bonds.