Distribution

Physical Description
Adult monk seals grow as large as seven feet in length and weigh between 400 and 600 pounds. Females are typically larger than males. Hawaiian monk seals have a maximum life expectancy of 30 years. The brownish pelt of a mature monk seal is often marked with scars from shark bites, cuts from sharp pieces of reef, and scars from being entangled in fishing gear. Click to hear a male monk seal (128K) warning another male not to come too close.

Diet and Feeding
Hawaiian monk seals feed on reef fishes, octopuses, eels, spiny lobsters, and other crustaceans that are found in relatively shallow waters. Adult monk seals can dive to 500 feet and remain underwater for as long as 20 minutes while foraging. Researchers believe that feeding strategies may differ between younger and older seals, and male and female seals. Seals can spend days foraging at sea before returning to the beach where they rest and digest their food.

Reproduction
Female monk seals reach reproductive age at six or seven years old. Most pups are born during the spring and summer months. Females give birth on sandy beaches near shallow protected waters. Newborn monk seal pups are jet black, measure about 3 feet in length, and weigh approximately 30 pounds. A pup nurses for about six weeks, during which time the mother seal does not leave its side. While nursing her pup, the mother seal survives entirely on the energy stored in her blubber. At the end of the nursing period the mother seal leaves her pup for good and begins feeding again. The newly weaned pup weighs between 150 to 200 pounds. It lives off of stored fat for a while, but must quickly learn to catch food on its own. Weaned pups lose a substantial amount of weight as they learn to forage, and many do not survive their first year.

Threats
Hawaiian monk seals are faced with many threats to their perilously small population. Monk seals are sensitive to human disturbance, habitat loss, and illness. In the French Frigate Shoals, starvation is one of the principal causes of monk seal mortality. Decreases in food availability may be a result of fisheries and changes in climatic weather patterns. Seals often ingest or get tangled in fishery nets and other trash in the oceans. Galapagos and Tiger Sharks attack and eat monk seals, particularly young pups. Finally, in a self-destructive behavior known as mobbing, aggressive male seals will attack females and immature seals until they are badly injured or killed.

Conservation
The monk seal population is currently estimated at 1,300 to 1,400 animals. In 1976, the Hawaiian monk seal was listed as endangered under the U.S. Endangered Species Act. It is the only endangered marine mammal found entirely within the United States. The National Marine Fisheries Service (NMFS) Protected Species Investigation is mandated to research and make recommendations on how best to manage the population of Hawaiian monk seals so that their numbers increase or stabilize. Conservation strategies include: identification and protection of critical habitat, research on the survival of the remaining population, removal of marine debris, and mitigation of human disturbance. Information is now available on monk seal reasearch and marine debris clean-up during the 2003 Field Season.