Vertebrate Zoology: Textbook - T. A. Dauda 2014

Metazoa
Infraslass Eutheria, or placental mammals
Order Pinnipedia

The order Pinnipedia unites mammals characterized by an elongated, spindle-shaped body, shortened limbs modified into flippers, and a short yet flexible neck (see Fig. 62). Their Hair coat is often sparse, short, and coarse, whereas subcutaneous fat deposits are exceptionally well developed.

External ear flaps are typically absent, but their Hearing is acute. Some species navigate using echolocation. While eyesight is poor, the SENSE OF SMELL is, by contrast, highly developed. Their dentition is largely similar to that of carnivores. Pinnipeds are predominantly distributed across polar and temperate latitudes. They generally inhabit coastal zones, though some venture into the open ocean. They spend the majority of their lives in the Water, where they feed and rest, hauling out onto ice or land for mating, giving birth, and molting. Pinnipeds are considered closely related to carnivores, having transitioned to an aquatic lifestyle. Twelve species are found in the waters of our country.

The largest of the pinnipeds is the walrus, reaching up to 4 m in length (females are about 3 m) and weighing around 1 t. Its body is covered with thick, wrinkled, calloused Skin, and the tail is extremely-short. The upper canine Teeth form massive tusks directed vertically downward. The hind flippers can be tucked forward to aid in terrestrial locomotion. The hair coat is sparse and entirely absent in older individuals.

The walrus inhabits coastal and shallow areas of the seas surrounding the Arctic Circle. Groups of 5 to 10 individuals occasionally gather into herds of up to 100 animals. Their primary diet consists of Mollusks, which they unearth from the seabed using their tusks. They establish haul-outs on shores and ice floes. Currently, walrus hunting is permitted exclusively for the indigenous populations of Yakutia and Chukotka.

Eared seals, as their name implies, possess small external ear flaps. Their hind limbs can be tucked beneath the body, assisting the animal when moving on land.

Steller sea lions and fur seals inhabit our territorial waters around the islands of the Sea of Japan, the Sea of Okhotsk, and the Bering Sea. Steller sea lions reach lengths of 2.3–3.6 m and weigh 200–800 kg, with a very sparse hair coat. In summer, they form rookeries on rocky islands, where males gather harems of 15–20 females, frequently sparking fierce fights. Pups are born only at the beginning of the following summer. Sea lions feed primarily on fish.

Fur seals are smaller than sea lions, measuring 1.1–2 m in length and weighing up to 115 kg. Their fur consists of coarse guard hairs and a dense, silky underfur, with males sporting a mane on their neck and HEAD. Fur seals stay close to islands, choosing wind- and wave-sheltered coastal areas for their rookeries. They are polygamous, with each male maintaining a harem of about 50 females. Gestation lasts nearly a year. Their diet comprises cephalopods, crustaceans, and fish.

True seals lack external ear flaps, and their hind flippers always point backward and cannot be tucked beneath the body. This group ranges from smaller species—such as the Caspian seal, Baikal seal, and ringed seal, measuring 1.2–1.5 m and weighing 40–90 kg—to larger ones, such as the hooded seal, bearded seal, and harp seal, measuring 1.5–2.8 m and weighing 150–400 kg. The fur of true seals is well developed, typically featuring striking spots and stripes. Most species inhabit the icy seas of both hemispheres, though certain species are also found in inland water bodies. For molting, mating, and pupping, they most frequently haul out onto ice, forming large aggregations. The main diet of most seals is fish, though they occasionally feed on benthic crustaceans and mollusks.

All pinnipeds are of significant commercial value, yielding blubber and leather utilized by humans. The harvesting of certain species—such as the ringed seal, harp seal, and harbor seal—is strictly regulated on a scientific basis to ensure population growth. Low-population and rare species, such as the Steller sea lion, fur seal, and grey seal, are protected by law.