The Hawaiian monk seal is a large warm–water seal. It is a member of the family of true seals because it does not have external ear flaps as fur seals and sea lions do. An average Hawaiian monk seal measures 7 to 7.5 feet (2.1 to 2.3 meters) long and weighs 450 to 550 pounds (204 to 250 kilograms).
Unlike in most other species, female Hawaiian monk seals are larger than their male counterparts. The color of a monk seal’s body varies slightly, from slate gray on top to silver gray underneath.
Hawaiian monk seals eat a variety of aquatic animals, including fish, eels, and octopi. They feed mainly along the shorelines of the islands they inhabit. Sharks often prey upon the seals.
Male Hawaiian monk seals choose a mate by wandering the beaches where females sun themselves. Since there are three times as many males as females, the females are often disturbed. When a male and female decide to mate, they do so in the water.
After a gestation (pregnancy) period of about 330 days, a female Hawaiian monk seal gives birth on the beach to a single pup. She nurses the pup for five weeks, during which time she fasts (does not eat). At birth, the pups are weak swimmers, and they must practice under their mother’s supervision until they are weaned.
Habitat and current distribution
The Hawaiian monk seal inhabits the islands and atolls (ring–shaped reefs surrounding lagoons) of the northwestern Hawaiian Islands. Breeding takes place primarily around Nihoa Island, Necker Island, French Frigate Shoals, Laysan Island, Lisianski Island, Pearl and Hermes Reef, the Midway Islands, and Kure Atoll. An estimated 1,200 Hawaiian monk seals remain in the wild.
Although some Hawaiian monk seals move between islands, most remain fairly close to their home beaches.
History and conservation measures
The population of Hawaiian monk seals increased slightly, however, in the early twentieth century as the animals sought out undisturbed, remote areas. During World War II (1939–45), humans began occupying more and more of the Hawaiian Islands, and the seals suffered.
Any intrusion into their range has a negative effect on the seals. When disturbed by humans, a pregnant female may abort her fetus. If a nursing female is disturbed, she may be unable to continue nursing and her pup may die.
Increased fishing activity in the Hawaiian monk seal’s range leads to conflicts between fishermen and seals. Many fishermen kill the seals, believing the animals steal their catch and damage their fishing nets. Some seals do become entangled in fishing nets and drown.
In 1940, a number of the islands and atolls in the Hawaiian monk seal’s range were designated the Hawaiian Islands National Wildlife Refuge. In 1976, this area was further declared a Research Natural Area.
These protective measures limit the number of human landings on the islands, insuring that Hawaiian monk seals—among the most endangered seals in the world—remain as undisturbed as possible.