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NATURAL HISTORY

HAWAIIAN MONK SEAL } Monachus schauinslandi
FAMILY: Phocidae

DESCRIPTION: Named for its resemblance to a Catholic monk, the Hawaiian monk seal has folds around its neck and is gray in color, with pelage often turning brown from weathering. Adult females weigh about 450 pounds, while males are smaller, weighing about 375 pounds. Pups are silvery gray with fuzzy black hair when they are born.

HABITAT: The Hawaiian monk seal is found on the sandy beaches and subtropical waters of the northwestern and main islands of Hawaii.

RANGE: The seal lives throughout the northwestern Hawaiian islands, with six main reproductive sites at Kure Atoll, the Midway Islands, Pearl and Hermes Reef, Lisianski Island, Laysan Island, and the French Frigate Shoals. Increasingly, seals have been observed on each of the eight main Hawaiian islands.

MIGRATION: Though monk seals tend to return to the same location each year, about 10 to 15 percent migrate along the northwestern Hawaiian islands. It is rare for seals to migrate between the main Hawaiian islands and the northwestern Hawaiian islands.

BREEDING: Monk seal mating behavior is rarely observed; however, it is known that they mate at sea. After mating, pregnant females haul out on shore to give birth, generally to a single pup. Birthing takes place at various times of the year, peaking in March and April. Pups are nursed for five to six weeks.

LIFE CYCLE: Adult monk seal females begin to give birth between the ages of five and nine. For males, the age of sexual maturity is unknown, but it is thought to be the same as females’. The species’ average lifespan is from 25 to 30 years.

FEEDING: Monk seals eat a variety of fish, cephalopods, and crustaceans, with common prey including reef fish, octopus, squid, lobster, and eel. These seals forage on the sea floor, usually on talus or sand near coral reefs, but sometimes in reef caves or coral beds.

THREATS: Limited food availability, shown to be caused by a variety of factors including overfishing, interspecies competition, and oceanographic and climatic changes, is believed to be primarily responsible for the ongoing decline of the Hawaiian monk seal. Other critical threats include entanglement in marine debris, shark predation, interactions with fisheries, habitat loss and disturbance, and disease. The seal’s entire terrestrial and marine habitat is threatened by global warming, which — in addition to altering ocean and climate conditions to contribute to food shortage — causes sea-level rise that obliterates pupping beaches.

POPULATION TREND: Since the mid 1950s, the monk seal population has precipitously declined, with only about 1,200 animals remaining. Scientists predict that the population will fall below 1,000 individuals within five years. Like the Mediterranean monk seal, also critically endangered, the Hawaiian monk seal will likely meet the fate of the now-extinct Caribbean monk seal if urgent action is not taken.

Photo by James P. McVey, NOAA