Monk Seal

Monk Seals

Scientific Classification

Common Name
monk seals
Genus Species
Monachus spp. (Comes from the Greek word monakhos, meaning "monk" or "solitary")

Fast Facts

Hawaiian Monk Seals are true seals and belong to the family Phocidae. Seals differ from sea lions (eared seals) in a number of ways, including having shorter, stouter flippers, and no visible earflaps. Newborn pups are born black, while weaned pups and older seals are dark gray to brown on their back and light gray to yellowish on their belly. Monk seals, along with bearded seals, are the only phocids that have two pairs of abdominal teats.
MALE Mature male Hawaiian monk seals may reach maximum lengths of 2.1 m (6.9 ft.).
FEMALE Hawaiian monk seal adult females may measure as much as 2.4 m (7.75 ft.).
Hawaiian monk seal adult males are slightly smaller than females
MALE Adult Hawaiian monk seal males can weigh up to 230 kg (510 lbs.).
FEMALE Hawaiian monk seal adult females may weigh as much as 270 kg (595 lbs.).
Hawaiian monk seals are known to eat a variety of fishes, eels, cephalopods, and crustaceans.
About 11 months; Hawaiian monk seal pups may be 1 m (3.4 ft.) long and 16 to 18 kg (35.2 to 39.6 lbs.) at birth. When weaned six weeks later they weigh 50 to 100 kg (110 to 220 lbs.)
Estral Period
Hawaiian monk seals unusually long breeding season lasts from December to mid-August, but most pups are born from March to June. Births occur during all months of the year, with most occurring during March to August.
Nursing Duration
5 to 6 weeks; In Mediterranean monk seals possibly as much as 16 to 17 weeks in some rare cases.
Sexual Maturity
4 to 6 years for both species; female monk seals first give birth at 4 to 10 years old
Life Span
Probably 25 to 30 years for both species. Hawaiian Monk Seals can live over 30 years of age but few live that long.
Hawaiian Monk Seals occur throughout the Hawaiian Island chain. Their six main reproductive sites are in the Northwestern Hawaiian Islands (NWHI) at Kure Atoll, Midway Atoll, Pearl and Hermes Reef, Lisianski Island, Laysan Island, and French Frigate Shoals. While sightings were previously rare in the main Hawaiian Islands (MHI), Monk Seals are now regularly seen there and births have been documented on all of the major islands. Sightings outside of the main range have occurred at Johnston Atoll, Palmyra Atoll, and Wake Island.
Hawaiian Monk Seals are non-migratory, and tend to remain near the atoll where they were born. However, approximately 10% of seals will relocate temporarily or permanently to other sites in the island chain, and long distance wanderers have been recorded.
Once abundant throughout the Mediterranean Sea, the southern Black Sea, and the northwestern coast of Africa, the Mediterranean monk seals are now scattered through just a small part of their historical range.
Both species inhabit coastal areas. When Mediterranean monk seals haul out, they usually prefer caves or grottoes, some with underwater entrances. Hawaiian monk seals typically haul out on sandy beaches.
Global: An estimated 500 to 1,000 individuals are all that remain of the Mediterranean monk seal. The Hawaiian Monk Seal population was observed to decline from 1,520 total individuals in 1983 to 1,209 in 2011. The number of mature individuals in the entire population in 2011 was 632, a reduction of 20.4% from the 795 mature individuals in 1983. The population overall has been declining for over 6 decades and current numbers are only about one-third of historic population levels.
IUCN: The Hawaiian monk seal is listed as Critically Endangered, the Caribbean monk seal is regarded as Extinct, and Mediterranean monk seal are listed as Endangered.
CITES: Both the Mediterranean monk seal and the Mediterranean monk seal Appendix I. The Caribbean monk seal is listed as Extinct.
USFWS: The Hawaiian monk seal is listed as Endangered

Fun Facts

  1. There are two living species of monk seals: Hawaiian monk seal (Monachus schauinslandi) and Mediterranean monk seal (Monachus monachus). A third species, the Caribbean monk seal (Monachus tropicalis) is believed to be extinct, no individuals have been observed since the early 1950s.
  2. Scientists believe Hawaiian monk seals to be "living fossils". The anatomy, behavior and physiology of this species of monk seal is only slightly different from monk seals that ranged along the eastern coast of the United States 14 to 16 million years ago.
  3. Monk seals are generally solitary, both on land and at sea. Even when seals gather together on land, they are not normally gregarious and only mothers and pups and recently weaned seals regularly make physical contact. On land, Hawaiian Monk Seals haul-out and breed on substrates of sand, coral, or volcanic rock. Sandy beaches with shallow protected water near shore appear to be preferred for pupping. Mediterranean monk seals are one of the least social pinnipeds when they are on shore, but may be more social in the water. These are considered one of the most critically endangered species of mammal in the world.
  4. Most dives that have been recorded have been less than 150 meters (488 ft.) deep, although some individuals dived to more than 550 m or 1,788 ft.
  5. Tiger sharks often prey upon Hawaiian monk seals as evidenced by shark bite wounds present on many monk seals. Other shark predators include gray reef and white-tipped reef sharks. Predation by sharks possibly helps explain why female Hawaiian monk seals seem to prefer beach sites adjacent to shallow water on which to give birth and raise their pups.
  6. Hawaiian Monk Seals are considered one of the most critically endangered species of mammal in the world.

Ecology and Conservation

Both Mediterranean and Hawaiian monk seals are endangered. Researchers estimate that the population has declined 60% since the late 1950s. Threats to monk seals are widespread and numerous. All three species of monk seals have suffered a long history of commercial hunting. Pollution and human development have also posed serious threats to monk seal populations. Hawaiian monk seals also succumb to lack of prey, tiger shark attacks, and even violent mobbing interactions with each other.

Monk seals are protected by the Endangered Species Act of 1973 (ESA). Hawaiian monk seals are also protected by the Marine Mammal Protection Act of 1972 and by other federal and local legislation.


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Jefferson, T.J. Leatherwood, S. and M.A. Webber. FAO Species Identification Guide. Marine Mammals of the World. Rome. FAO, 1993.

Rauzon, M.J. Isles of Refuge: Wildlife and History of the Northwestern Hawaiian Islands. Honolulu. University of Hawai'i Press. 2001.

Reeves, R.R., Stewart, B.S. and S. Stephen. The Sierra Club Handbook of Seals and Sirenians. San Francisco: Sierra Club Books, 1992.

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Riedman, M. The Pinnipeds: Seals, Sea Lions and Walruses. Berkeley and Los Angeles. University of California Press. 1990. IUCN Animal Info-Mediterranean Monk Seal

Littnan, C., Harting, A. & Baker, J. 2015. Neomonachus schauinslandi. The IUCN Red List of Threatened Species 2015: e.T13654A45227978. Downloaded on 01 October 2018.

NOAA Fisheries – Hawaiian Monk Seal Species Profile. Downloaded on 01 October 2018.