Taxonomy/Description

Monk seals belong to the Mammalian Order Pinnipedia, in the family Phocidae.  Other members of Phocidae include elephant seals, gray seals, and leopard seals.  Phocids are referred to as true seals.  They are distinguished from other pinnipeds by their inability to support their body using their hind limbs.

The monk seal's scientific name generic name, Monachus, means "monk".  This probably describes the seals' occasional solidarity, as well as their large rings of neck fat which resemble a monk's hood.  The Hawaiin monk seal's specific name, schauinslandi, refers to a German zoologist, Professor H. H. Schauinsland (1857-1937), responsible for discovering the seal.   The Mediterranean monk seal's specific name monachus, which means "monk".  The Caribbean monk seal's specific name, tropicalis, means "belong to tropical regions", which refers to the tropical environment of the Caribbean.

Monk seals exhibit morphological characteristics developmentally more primitive than prehistoric seal fossils dating 14.5 million years.  This group of seals is the most ancient-looking of all seal species.  The Hawaiian monk seal separated from an Atlantic-Caribbean monk seal population 15 million years ago.  They share similar coloration with the Caribbean monk seals.  Both are brownish gray dorsally, with yellow underbellies and muzzle.  The Mediterranean monk seal is also brownish gray, but has a distinctive white patch on its underside.  Monk seals range in size from 6-7.5 feet.  Mediterranean monk seals are the largest species, usually weighing about 700lbs.  Males and females are similar in weight and length.  Hawaiian monk seal females weigh less about 550lbs, and males weigh about 370lbs.  Males are significantly smaller than females.  Caribbean monk seals are the smallest, weighing about 350lbs.

Habitat/Diet

Monk seals are the only tropical phocid species.  All other seal species live in the temperate and polar regions close to the Arctic or Antarctic.  The Hawaiian monk seal is endemic to the southwestern beaches of the northwestern islands and atolls of the Hawaiian archipelago.  In fact, along with the hoary bat, Hawaiian monk seals were one of two mammal species present on the Hawaiian archipelago before humans.

Mediterranean monk seals inhabit a variety of nations bordering the Mediterranean and Aegean Seas.  Populations are found in Greece, Turkey, Albania, Morocco, and Algeria.  The mid-Atlantic populations live on the archipelagos and coast of Mauritania.  Secluded beaches and caves away from human disruption are the preferred locations for monk seals.  The beaches of the Mediterranean have become so crowded that Mediterranean monk seals haul out in ocean caves, some only accessible from underwater. 

Caribbean monk seals once inhabited islands throughout the Caribbean Sea and the Gulf of Mexico.  Formally declared extinct in the 1996 IUCN Red List of Threatened Animals, the location of any surviving monk seals is unknown.  The last confirmed sighting of the species occurred between Jamaica and Honduras, on the Island of Seranilla Bank in 1952.  More recent sightings within their former range have been unconfirmed.

Hawaiian and Mediterranean monk seals feed primarily on lobster, octopus, and a variety of fish.  Fish prey species include eel, tuna, sardines, flatfish, and mullet.  The Caribbean monk seal was poorly studied before it became extinct.  Consequently, its diet is mainly unknown.

Behavior/Reproduction

Hawaiian and Caribbean monk seals evolved on islands without land predators.  Sharks are their main predator, especially the Galapagos shark.  A lack of land threats resulted in relatively docile behavior towards terrestrial animals.  Both species became easy targets for hungry sailors.  Despite the fear of land intruders by Hawaiian and Caribbean monk seals, all three species are easily disturbed by human presence.  Seals will abandon pupping beaches.  Disruption of nursing often results in the death of the pup.  Due to their conflicting ranges with human tourism, this disruption has become a serious conservation threat.

Hawaiian monk seal, Monachus schauinslandi

Monk seals lead solitary lives.  They are not migratory species.  Pupping beaches and feeding grounds are within the same range.  Seals return to beaches each year to pup.  Males travel the beaches within their range for receptive females.  A breeding practice by male Hawaiian monk seals, called mobbing, has become a conservation threat.  Females and juveniles of both sexes are attacked by groups of males intending to breed.  In the Hawaiian monk seal population, males outnumber females three to one in some colonies.  Mobbing has become a threat to monk seal survival in those colonies.  Breeding for Hawaiian monk seals occurs in May and June.  Breeding for Mediterranean monk seals occurs in October and November.  Delayed implantation occurs, and the time between fertilization and birth is about one year.  Monk seals of all species are 20-30lbs in weight and about three feet in length at birth.  A dark brown or black coat is characteristic of all species.  Mediterranean monk seal pups have a characteristic yellow patch on their underside.  The female seal does not feed during the nursing period.  She relies on stored fat.  Seals are weaned at about six weeks.  They weigh between 150-200lbs at weaning age.  The black lanugo coat is molted at this time.  Mediterranean monk seals of both sexes reach sexual maturity at 4-6 years.  Hawaiian monk seals of both sexes mature sexually at 5-9 years. The lifespan of a monk seal is 20-30 years.

Conservation

The Caribbean monk seal was formally declared extinct in the 1996 IUCN Red List of Threatened Animals.  The Mediterranean monk seal is the most endangered pinniped, with fewer than  400 individuals remaining.  The Hawaiian monk seal is the second most endangered pinniped, with about 1,300 individuals remaining.  The tropical environmental preferences of these species place them in direct competition with humans, who also enjoy tropical climates.  Monk seals are easily disturbed by the presence of humans as well.  This behavioral characteristic prevents the coexistence of monk seals and tourists on European and Hawaiian beaches.  Nets from commercial fishing boats incidentally drown monk seals.  The bioaccumulation of toxins in monk seals from ocean pollutant is another cause of death.  Also, Hawaiian and Mediterranean monk seals are both protected under the United States' Marine Mammal Protection Act of 1972 and the Endangered Species Act of 1973.

Hawaiian monk seal populations suffer from a variety of threats.  Ciguatera, a toxin that naturally occurs in dinoflagellates of the marine food chain, builds up in Hawaiian monk seal prey species.  Significant die-offs have occurred from this poison.  This species recovered minimally during the early 20th century.  During this time the northwestern Hawaiian Islands were designated as a bird reserve.  The advent of World War II altered the fortune of the monk seal.  Naval bases were established, and naval engagements took place throughout the Hawaiian archipelago.  This disruption caused the species to decline between 1950 and 1980.  Nature preserves and sanctuaries have since been established to guard Hawaiian monk seals from human disruption.