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Hawaii - The Big Island to Kure Atoll
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The Hawaiian Monk Seal - Only in Hawaii
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The monk seal species known as Monachus schauinslandi may have gotten its common name (monk seal) from the fact that its round head covered with short hairs gives it a kind of Friar Tuck appearance or from the fact that it lives a "monk-like" or solitary existence.
Lifespan: Life expectancy is 25 to 30 years.
Average Length: Females grow slightly larger than males and display more variation in weight. Adult females range between seven and eight feet while adult males measure approximately seven feet at maturity. Newborn pups are 30 to 40 inches in length.
Average Weight: 300 to 400 pounds for adult males and 400 to 600 pounds for females (depending on reproductive state); 30 to 40 pounds for newborn pups.
Color: Adults have a brownish pelage (coat); juvenile pelages are silvery gray on the back and sides and creamy white on the belly, chest and throat; pup coats at birth are black and woolly, with fuzzy, short hair. Newborn pups display a jet-black coat.
Physical Description: Monk seals are brownish when mature. They typically have scars both from sharks (such as tigers, gray reef and white-tips) and from being entangled in fishing gear. Mature females may also bear scars from aggressive males encountered during mating.
Distinguishing Characteristic: During the first molt (shedding of outer covering) after birth, the pelage hairs individually fall out. During successive annual molts, the epidermis peels off with the old hair to reveal the bright new pelage underneath. This epidermal molt is like the snake's shedding of skin. The only other seal known to molt like this is the elephant seal.
Distribution: The three species of monk seals are widely separated by geographic region: Mediterranean (critically endangered), Caribbean (thought to be extinct) and Hawaiian (endangered).
Mediterranean monk seals are found in the Aegean Sea, along the Mediterranean coast of Morocco, along the Algerian coast of Tunisia and in the eastern Mediterranean Sea. Hawaiian monk seals are normally found on the leeward (southwest) sides of the northwestern Hawaiian islands, and occasionally sighted in the main Hawaiian islands. In June 1997, the first birth on Maui was recorded.
Natural History: The thickness of monk seal blubber is comparable to that of seals living in frigid climates. Monk seals keep cool on hot, windless days by lying on damp sand with light ventral pelage exposed at the water's edge and by making wallows into cool sand layers.
Monk seals normally don't stay on dry, hot, upper beach levels except during cool, windy or cloudy weather. Seals are also very inactive when ashore. Their respiration includes long periods of breath-holding, and the heart ratio that accompanies holding their breath is low. These behaviors result in low levels of metabolic heat production and are excellent natural adaptations to heat exposure.
The three species of monk seal are part of the family Phocidae. Monachus is the genus, and it contains the most primitive of all seals. Monk seal ancestors originated in the North Atlantic Ocean at a very early date. The Hawaiian monk seal became separated from the Atlantic-Caribbean members of the genus as early as 15 million years ago.
Perhaps because of their primitiveness, monk seals seem far more sensitive than other phocids to human intrusion of their environment. Pregnant females and mothers with nursing young appear greatly upset when approached.
These disturbances may cause increased deaths among Hawaiian monk seal pups. Monk seals are solitary, both in the water and onshore. When loose groups form on beaches, they gather because the local environment conditions are favorable. Except for mothers with pups, resting seals avoid bodily contact with each other.
Monk seals can dive to at least 500 feet. The seals remain underwater for as long as 20 minutes while foraging (searching for food).
Behavior: Monk seals vocalize from when they are young into adulthood. Pups utter "mwaa, mwaa, mwaa" and, when disturbed, an explosive "aaah" or "gaah."
An alarmed adult sound consists of a "bubbling" that originates deep in the throat (with the mouth either open or closed). The bubbling resembles that of water from a jug.
Status: Monk seals, although totally protected, remain one of the most endangered of all seals. It is estimated that fewer than 1500 Hawaiian monk seals exist today. The Hawaiian monk seal was officially designated endangered November 23, 1976 and is protected by the Endangered Species Act and the Marine Mammal Protection Act. It is illegal to kill, capture or harass monk seals.
Monk seal species have shown alarming population declines in recent years due to the rapid spread of human activity to even the most remote and isolated areas. Many monk seals were clubbed to death for meat, oil and their skin. In Hawaii, these factors have contributed to the seal's decline:
death from predation by sharks
lower pup survival as the result of human disturbances
ciguartera intoxication
entanglement in fishing nets and debris
Reproduction: Adult males constantly cruise along their favorite beaches in spring and summer, searching for receptive females. Significant breeding areas for Hawaiian monk seals are mostly under the protection of the Hawaiian Islands National Wildlife Refuge, which is administered by the U.S. Fish and Wildlife Service.
Monk seals are polygynous, which means they mate a number of times with a number of different partners. (Adult males out-number adult females by about three to one.)
Monk seals mate in the water.
Monk seals give birth between mid-December and mid-August, with the peak breeding season occurring in May. The gestation period (from fertilization until birth) is about one year.
Mothers usually give birth (called pupping) to small black fuzzy pups on sandy, coral beaches that are backed by shrubs; utilizing the shrubs for shelter during the night.
Successful pupping also occurs on beaches where sheltering vegetation does not exist and, in recent years, pups have been born on rocky beaches. Apparently, however, when human activity forces pregnant females to desert their traditional pupping beaches to bear pups, pup survival is greatly reduced.
Mothers do not feed while nursing. Mothers nurse their pups for five to six weeks, and subsist entirely on energy stored in their blubber. A mother may lose up to half her body weight during the nursing period. At weaning, pups are enormously fat. Their weight has quadrupled since birth, to about 140 pounds. The body length, however, shows little change. After weaning, while the young seal learns to fend for itself, it steadily loses weight. At one year of age, juveniles weigh about 100 pounds.
Feeding: Monk seals feed on fishes and invertebrates both within atoll lagoons and in deeper water offshore. Common foods for monk seals are spiny lobster, eels (except conger and moray), flatfish, small reef fish, larval fish and octopus. Monk seals are also assumed to prey on pelagic (open ocean) species, but only because the monk seal is known to travel long distances in the open ocean.
Monk seals may eat as much as ten percent of their body weight in a day. They sometimes spend many days at sea before returning to the islands where they sleep and digest their food.
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