The Ribbon seal (also Banded seal; scientific name: Histriophoca fasciata) is one of 19 species of marine mammals in the family of true seals. Together with the families of eared seals and Walruses, True seals form the group of marine mammals known as pinnipeds. This species spends late winter and spring on pack ice, becoming pelagic in the summer months.
The common name ribbon seal reflects the broad circumferential banded markings on the coat of this species.
Ribbon seal. Source: M. Cameron/NOAA
Kingdom: Animalia (Animals)
The adult coat of a ribbon seal is most easily described as a dark background with four light colored stripes running in a circle around the animal. One stripe encircles the neck, another encircles the mid-posterior portion of the seal's body, and the other two stripes start ventrally and encircle the fore flippers on either side. Although this is the general pattern for all ribbon seals, there can be great individual variability as to the shade and precise location of the stripes. Newborn and juvenile ribbon seals do not have this striped pattern; as newborns are completely white, while juvenile seals are dark anteriorally and dorsally, and grayish posteriorly and ventrally. Males tend to be darker than females.
Other ribbon seal physical characteristics include large eyes and small teeth. An adult will grow to about 1.6 metres and weigh 70 kilograms.
Males have a well-developed air sac extending from the posterior trachea. The function is unknown but it is likely to be used in underwater vocalizations that may be to attract females and compete for mates.
Adult females become pregnant once a year, giving birth sometime in April or May. Typically ribbon seals give birth to one pup with the birthing occurring on ice flows. Nursing lasts up to a month, a time during which the weight of the pup will double. As soon as the pups are weaned, adults will mate again. Ribbon seals employ a delayed implantation of two or three months, this is most likely to assure the presence of ice at the time of birth. After weaning, pups spend a lot of time practicing diving and learning how to move on the ice.
The presence of standing ice is very important to Ribbon seals during the winter and spring months. They will rest on the ice, often very far from the water. Ribbon seals seem to be unconcerned with the threat of predation, as they will allow their young to wander far from the mother's location for long periods of time. Individuals tend to be solitary; females will shelter their pups however. As ice begins to melt in the late summer some populations will move further north with the receding ice-line. Most populations become pelagic in the summer months.
Little is known about the feeding behaviors of Ribbon seals, but they most likely dive for food in ways similar to other seals.
One characteristic that is different in Ribbon seals when compared to most other seals is the method of locomotion on ice. The ribbon seal will slither along the ice using side-to-side motions to propel itself, rather than inching forward with the front flippers as do other seals.
Ribbon seals are found in coastal areas of the north Pacific Ocean and in the seas bordering Alaska and Russia: Bering Sea, Chukchi Sea, Beaufort Sea and Okhotsk Sea.
Habitat and ecology
Ribbon seals are restricted to the cold waters of the northern Pacific Ocean and certain other northern hemisphere boreal seas. In winter and spring they forage and raise offspring on coastal ice flows; summer months are spent in the open ocean. Predators of this seal species are the Orca, Greenland shark and Polar bear.
Ribbon seals eat primarily fish, taking fish species depending on their relative abundance in the area. Ribbon seals also consume squid, shrimp, and crabs. Juvenile seals have been reported to include a significant proportion of crustaceans into their diet.
The conservation status of the Ribbon seal is considered Data Deficient by the IUCN, due to the species wide ranging habits in harsh northern climates, with little land exposure of the species; however, some listings of the species status describe the conservation status as Least Concern. An estimated quarter of a million individuals were estimated to exist as of the 1970s. It is thought that the number of Ribbon seals in the wild is increasing due to relatively recent decreased hunting pressure. However, no surveys of Ribbon seal populations have been completed since the mid 1970's. The largest human-created problem facing ribbon seals are accidental nettings of individuals in Pacific fishing areas.
Economic Importance for Humans
Presently, approximately 100 Ribbon seals are taken annually for subsistence purposes by natives of the areas in which the seal lives. From the 1950s until the 1980s Russian fisheries killed large numbers of ribbon seals for their pelts meat, and oil; the annual Russian take in each of those years was estimated between 6500 and 23,000 Ribbon seals. Recently commercial scale hunting has been abandoned.
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