The Hawaiian Monk Seal is one of the rarest marine mammals in the world. It is epidemic to Hawaii and is one of the two remaining species in the "true seal" family.


Adult Hawaiian Monk Seals have silvery-grey colored backs with lighter creamy coloration on their underside. The back of these mammals may become darker with age, especially in males. Adult females are generally larger than males.

These seals undergo a complete molt each year, typically between April and December. The seals shed all of their hair and a layer of skin within approximately 7-10 days and generally remain on shore the majority of the time.

Adults have a body length of 2.1-2.3 m (7-7.5 ft) and their weight is 170-205 kg (375-450 lbs). Pups are jet black, and weigh 16 kg (35 lbs). They are 1 m (3 ft) at birth.

Life History

Monk seals haul out to rest or sleep, pup, and molt and should not be disturbed. 


Hawaiian Monk Seals eat reef fish, squid, octopus, and crustaceans.


Females typically mature between 5-6 years of age, and it is unknown when males mature.

Mating takes place in the water. To mate, males bite the back of females while mating and can rip skin and blubber.

Females tend not to give birth on beaches where there is much human activity. The gestation period is 10-11 months. Births can occur during any month, but most pups are born between late March and early April.

Females nurse their pups for approximately 5-6 weeks. Seal milk is very rich, which allows pups to gain weight rapidly. Pups can quadruple more than their initial weight before weaning. The mother seal loses a tremendous amount of weight while nursing.

They can live for 25-30 years.


Hawaiian Monk Seals are endemic to the Hawaiian archipelago and found mostly in the Northwestern Hawaiian Islands, although sightings reported from the main Hawaiian Islands are increasing. Less than 1,200 seals are scattered throughout the entire archipelago.

Most seals remain at their birth place for life, but there is some inter-atoll movement. 


This seal is endangered and its population is decreasing. Primary natural factors affecting monk seal recovery include predation by sharks, aggression by adult male monk seals, and reduction of habitat and prey linked with environmental change. Entanglement in marine debris such as fishing nets and lines and plastic rings are other sources of monk seal death.



  • The Hawaiian name for the Hawaiian Monk Seal is ʻIlio-holo-i-ka-uaua.
  • Hawaiian Monk Seals inhabit tropical waters, unlike most seals who inhabit frigid waters.


  • Hawaiian Monk Seal by U.S. Fish & Wildlife Service.
  • Hawaiian Monk Seal by National Geographic.
Community content is available under CC-BY-SA unless otherwise noted.