Hawaiian monk seal (Monachus schauinslandi)

Spanish: Foca Fraile De Hawaii
GenusMonachus (1)
SizeMale length: 2.1 m (2)
Female length: 2.3 m (2)
Male weight: 170 kg (2)
Female weight: 205 kg (2)

Classified as Critically Endangered (CR) on the IUCN Red List (1), and listed on Appendix I of CITES (3).

Hawaiian monk seals are the only true seals to be found year-round in tropical waters (2). After the annual moult, this monk seal is a silvery grey colour on the back, with cream colouring on the throat, chest and underside (4). Over time the coat looks brown above and yellow below; males, and some females, turn almost black with age (2). Certain individuals may have a red or green tinge or spots due to algal growth (4). Pups measure about one metre at birth and have a silky black coat, which moults after around a month into the silvery adult-like fur (5).

The main reproductive and foraging sites are on and around the largely uninhabited and remote Northwestern Hawaiian Islands of French Frigate Shoals, Laysan Island, Lisianski Island, Pearl and Hermes Reef, Midway Atoll and Kure Atoll. Monk seals also breed in lower numbers at Necker and Nihoa Islands in the Northwestern Hawaiian Islands and in the main Hawaiian Islands, and have also been seen at a few sites outside of the Hawaiian Archipelago (6) (8).

Found on the coral atolls and rocky islands of the Northwest Hawaiian Islands, in tropical waters (2).

Monk seals are predominately solitary although females with young may be observed near each other due to limited areas offering the preferred habitat type for pupping (8). Females are sexually mature at around five to six years of age and tend to give birth to a single pup; the majority of births occur between March and June (4). Females suckle their young for around six weeks (8). Males become extremely aggressive during the breeding season and groups of males can sometimes kill females or juveniles in what is known as ‘mobbing’ during this time (2). Hawaiian monk seals have a similar fat content to their relatives that inhabit cooler, polar waters and have developed behavioural adaptations to cope with the warmth of their tropical habitat; they are mainly nocturnal, spending the day hauled out on sandy beaches often wallowing in wet sand by the waters edge (5).

Monk seals feed on a variety of marine animals from fish, including eels, to cephalopods such as octopus and squid (4). They forage at depths of up to 100 metres, but are known to dive to 500 metres, and may travel large distances to foraging locations (5).

During the 1800s, Hawaiian monk seals were persecuted for their meat, hides and oil; their habitat was also disturbed by bird guano and feather collectors (6). Despite protection, numbers of these seals continue to decline; an average decline of 3% a year occurred between 1985 and 1999 (6). A lack of food resources, especially around French Frigate Shoals has been cited as the cause of high juvenile mortality and the presence of severely emaciated individuals (7). In addition, entanglement in marine debris that accumulates in these islands from vast areas of the Pacific, as well as disturbance, further threatens this species (6). Non-human threats such as predation by sharks and the prevalence of violent ‘mobbing’ behaviour of mature males, also play a part in the decline of monk seal numbers (4).

The Hawaiian monk seal has been listed on the United States Endangered Species List since 1976 and the National Marine Fisheries Service (NMFS) is responsible for the management of the population (7). Major colonies are surveyed annually and beach counts help to give an indication of the state of each breeding population (7); flipper tagging has been carried out since the early 1980s (6). The Northwest Hawaiian Islands lobster fishery was closed in 2000, and this may help to increase prey availability (6). In 2000, the Northwestern Hawaiian Islands Coral Reef Ecosystem Reserve was established, which should help to protect the habitat of this unique seal (7).

To learn more about the Critically Endangered Hawaiian monk seal see: 

Authenticated (18/02/05) by Bill Gilmartin, Monk Seal Recovery Team.

  1. IUCN Red List (November, 2008)
  2. Macdonald, D. (2001) The New Encyclopedia of Mammals. Oxford University Press, Oxford.
  3. CITES (November, 2002)
  4. Monachus-guardian.org (November, 2002)
  5. Animal Diversity Web (November, 2002)
  6. National Marine Fisheries Service (November, 2002)
  7. Gilmartin, B. (2005) Pers. comm.
  8. Marine Mammal Commission (November, 2002)