General characteristics: The spotted seal is of intermediate size when compared to the other true seals occurring in waters adjacent to Alaska. It is roughly the size of harbor and ribbon seals, larger than the ringed seal, and considerably smaller than the bearded seal. Very large spotted seals may be as heavy as 270 pounds (123 kg), but most physically mature adults of both sexes weigh between 180 to 240 pounds (81 to 109 kg). Length of grown seals is between 56 to 67 inches (142 to 170 cm). Newborn pups weigh 18 to 26 pounds (8 to 12 kg) and average about 33 inches (84 cm) long. Like ringed and ribbon seals, they are born with a dense coat of whitish hair which provides insulation until the blubber layer is developed. This hair (lanugo) is shed by 4 to 5 weeks of age. The new hair is similar in appearance to that of adults.

Spotted seals have the same complement of 34 teeth that ringed, ribbon, harbor, and bearded seals do. The teeth are strongly rooted. The snout of spotted seals is somewhat elongated, resembling that of most dogs.

 

Biology: Maximum life span of spotted seals is about 35 years, although few live beyond the age of about 25. Physical maturity is obtained between 7 and 8 years of age, but animals continue to increase in size throughout life. Females reach sexual maturity at 3 to 4 years of age and males at 4 to 5. They are annual breeders, and mating occurs in late April to early May. Unlike other seals of the Bering Sea, spotted seals appear to be monogamous. Pairs are formed as early as late February and break up after the breeding season. Pupping occurs anytime from early April to the first part of May, although the peak is during the first two weeks of April. Pups are nursed for three to four weeks, during which time they more than double in weight. Adult females mate about the same time their pups are weaned. During the first few weeks after weaning, pups seem to spend most of their time on the ice, apparently slowly achieving proficiency at diving and feeding. During this initial adjustment to independent life, they lose a considerable amount of weight as they rely on their accumulated fat for energy. It is during May and June that starveling pups are most commonly found on beaches.

 

Food habits: Most studies of the food habits of spotted seals in the Bering Sea are based on samples obtained in April to June. In general, studies show that principal foods are schooling fishes, although the total array of foods is quite varied. There are geographical and seasonal differences in their prey. During the spring-early autumn period, major prey items in Karaginski Bay and the Gulf of Anadyr include Arctic cod, sand lance, sculpins, flatfishes, cephalapods (mainly octopus), and a variety of shrimps. Arctic cod are a major food item in the northern Bering Sea, while pollock and capelin are dominant items in the central and southeastern parts, respectively. Pups feed primarily on crustaceans, mainly small shrimps. Along the coast these seals feed on herring, capelin, saffron cod, some salmon (especially in lagoons and river mouths) and smelt. Many other items of lesser importance are consumed. Data from satellite tags suggests that they dive to near the bottom to feed.

 

Seasonal movements: In Alaska waters, spotted seals winter in the southern part of the Bering Sea pack ice. By March-April they are concentrated mainly in the ice front at or near the southern ice margin in a band that extends from Bristol Bay in the east to Karaginski Bay in the west. Though continuous, their distribution is not uniform. Centers of abundance are in western Bristol Bay, near the Pribilof Islands, and in the eastern Anadyr to Karaginski Bay region. In May-June they rest and molt on the receding and melting pack ice, forming large concentrations on the various ice remnants that persist. Their movements are mostly northward and toward the coast.

By late summer-early autumn they are found along the entire northwestern coast of Alaska, though they are not abundant in the Beaufort Sea. They are not limited to the coastal zone. Recent satellite tagging studies have shown that some seals make extensive feeding trips of several hundred miles from the Chukchi Sea coast to the western Chukchi Sea and back. In autumn-early winter they move southward and away from the coast just before and during freeze-up. Some seals move down the Chukotka Peninsula coast and then into the central Bering Sea. Others seem to move down the Alaska coast. By midwinter they are again concentrated in the southern part of the Bering Sea pack. It is noteworthy that spotted seals are abundant along the northwest coast during months of open water and are replaced in that zone by ringed seals when extensive ice is present.

 

Behavior: Spotted seals are comparatively wary and difficult to approach openly. They form large aggregations on the ice and at favored locations on lands. The largest land aggregations in Alaska are at Kasegaluk Lagoon in the Chukchi Sea, near Cape Espenburg in Kotzebue Sound, and on bars and shoals in Kuskokwim Bay. Several thousand seals may be hauled out together in these areas. There is considerable individual variability in the amount of time spotted seals spend hauled out, ranging from 6 to 30 percent.

Little is known about their vocalizations. They do not seem to be especially vocal except when in molting groups on the ice. When encountered in such groups, they make a variety of sounds describable as growls, barks, moans, and roars. Individuals in molting groups give the appearance of being rather continuously agitated, though they are not in bodily contact with nearby seals. On land and ice, spotted seals move about in the typical wriggling or inchworm locomotion of most true seals.