Seal

Overview
Seals are large aquatic mammals, inhabiting both land and sea, and are part of the “true seal” family. True seals lack external ear flaps, making them more streamlined, but they can steal hear. Seals are less adapted compared to other aquatic mammals, with flippers instead of tails. Seals are distinguished by their inability to pull their flippers under their bodies to walk, demonstrating a very awkward movement on land. Their form of locomotion is termed galumphing where they wriggle their front flippers and abdominal muscles to move short distances. Seals are quite efficient swimmers.

Most seals live in colder waters near the Arctic and Antarctic regions, but some do occupy waters in warmer climates, such as Hawaii and California.

Diet
Most seals dine on fish and squid, though some species have diets that are more diverse. The leopard seal in the Antarctic, for example, eats penguins and small sea birds. They are known to give chase to humans on land and threaten scuba divers in water.

Reproduction
For the most part, seals mate on ice or land. All seals give birth out of water. In most land-mating instances, seals will form temporary colonies, called “rookeries,” and a harem-type system ensues where the largest, strongest male seals mate with several female seals and guard them from other males.

Ice-mating seals are slightly different in that they don’t practice a harem system. While they do form widely spread colonies on ice, most ice-mating seals are monogamous, and males and females are roughly the same size and appearance.

On average females breed once a year and give birth to a single pup (12 months after mating). The size of the newborn seal depends on the species.

Baby seals grow very fast to build a layer of blubber, which they are not born with. Seal milk is rich in fat and protein, and female seals will nurse their young anywhere from a few days to a couple months, depending on the species. Seal milk has a high fat content, roughly 40 to 50 percent, which helps the babies develop quickly.

Threats
Prized for their hides and as a food source for indigenous people, seal hunting (or sealing) has long been a tradition of both personal and commercial interests. Seal populations quickly diminished when commercial hunting took hold. Hunting continues to this day, though regulations are strict for the most part. In Canada, for example, seal hunting season occurs from November through May, but most of the hunting occurs in late March. Despite protests from several conservation groups, the Canadian prime minister allows seal hunting to continue.

Outside of commercial hunting, threats to seals remain. Each year thousands are caught in fishing nets and drown. Pollution, climate change, and loss of habitat due to the development of coastal areas also place stress on the survival of seals.