Monk Seal Fact Files
Hawaiian Monk Seal
In contrast to the Mediterranean monk seal, for which recorded history dates back more than 2,500 years, nothing is known of the Hawaiian monk seal in antiquity. Written reports began with the Russian explorer Lisianski, who in 1805 observed seals on the island that now bears his name. Records from voyages of the Aiona in 1824 and the Gambia in 1859 suggest that the species' distribution and abundance were reduced by unregulated seal hunts in the early to mid-1800s. The Gambia, for example, reportedly returned to Honolulu with 1,500 skins (although the authenticity of this report has been questioned). The seals were killed not only for pelts and oil; they were also killed for food by ship-wrecked sailors and by guano and feather hunters. The effect of such killing on the distribution and abundance of Hawaiian monk seals was never documented, but presumably it was severe. - From: Ragen & Lavigne, 1999.
- Order: Carnivora
- Family: Phocidae
- Subfamily: Monachinae
Distribution and Habitat
The Hawaiian monk seal is found on the sandy beaches and in the surrounding waters of the northwestern Hawaiian Archipelago, known as the Leeward Chain: Kure Atoll, Midway Atoll, Pearl and Hermes Reef, Lisianski Island, Laysan Island and French Frigate Shoals. Small populations also occur at Necker and Nihoa Islands. However, little is known of their offshore habits or distribution.
Threats to the Species
Like the Caribbean and Mediterranean monk seals, the Hawaiian monk seal was easily exploited by hunters, whalers and fishers in the 1800s. Today, anthropogenic threats include: incidental capture in fishing gear, ingestion of fisheries debris or toxic substances, intentional kills and a decrease in food availability for some subpopulations (e.g. French Frigate Shoals). The Hawaiian monk seal, like the other monk seal species, is sensitive to human disturbance and habitat loss. These factors, along with shark attacks, mobbing (a behaviour where females and immatures of both sexes are wounded, sometimes fatally, by the aggressive sexual behaviour of some males), and an inherently slow reproductive rate continue to threaten the remaining Hawaiian monk seal population. Conservation strategies include: the protection of critical habitat, identification of main reproductive habitats, research on the survival of various age and sex classes, rehabilitation and release of undersized pups, removal of marine debris and the mitigation of human disturbance. A captive breeding program is also advocated by some scientists.
Hawaiian monk seal females reach a length of 2.3 m and weigh up to 273 kg; males are slightly smaller, measuring up to 2.1 m and weighing about 230 kg. Adults are silvery-grey on the back, fading to cream on the throat, chest and belly. Additional light patches may also be found on the body. Over time, the coat looks brown above and yellow below. Males, and some females, turn a dark brown or black with age. Some Hawaiian monk seals have a red or green tinge from algal growth. Monk seals tend to be solitary, both on land and in the water. The breeding season occurs between December and mid-August although most pups are born from March to June. Pups, weighing approximately 16-18 kg and measuring 1 m, are born with a long, woolly, black coat which is shed at about six weeks of age. At about this time, the pups are weaned. Females reach sexual maturity at 5 or 6 years of age, and may live to be 20-25 years old. Monk seals, like most monachines seals, walruses, fur seals and sea lions, have four mammae. Monk seals feed on a variety of fish, cephalopods and crustaceans.
In 1976, the Hawaiian monk seal was listed as endangered under the U.S. Endangered Species Act. They are also listed as endangered in the International Union for the Conservation of Nature and Natural Resources (IUCN) Red List of Threatened Species. Hawaiian monk seals are also listed on Appendix I of the Convention on International Trade in Endangered Species (CITES). Between 1958 and 1996, mean beach counts of the main reproductive populations declined by 60%. Current population estimates range from 1300-1400 animals and the population continues to decline; from 1985 to 1996 the rate of decline was about 4% per year. While different island subpopulations exist, they are all managed as a single stock by the US National Marine Fisheries Service (NMFS).
Atkinson, S. 1998. Conservation strategies for declining monk seal populations. Workshop on the biology and conservation of the world's endangered monk seals. WMMSC Conference, Monaco. 19-20 January 1998.
IUCN. 1996. 1996 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland.
Jefferson et al. 1994. Marine mammals of the world. FAO and UNEP. 320pp.
Lavigne, D.M. 1999. The Hawaiian Monk Seal: Management of an Endangered Species. In J. R. Twiss Jr. and R. R. Reeves (eds.) Conservation and Management of Marine Mammals. Smithsonian Institution Press. In Press.
Ragen, T. J. & D. M. Lavigne. 1999. The Hawaiian Monk Seal: Biology of an Endangered Species. In J. R. Twiss Jr. and R. R. Reeves (eds.) Conservation and Management of Marine Mammals. Smithsonian Institution Press. In Press.
Reijnders et al. 1993. Seals, Fur Seals, Sea Lions, and Walrus. Status Survey and Conservation Action Plan. IUCN Seal Specialist Group. Gland, Switzerland. 88pp.
Adapted from Marine Mammal Fact Sheet Series: Hawaiian Monk Seal. IMMA Inc.
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