Hawaiian Monk Seal Natural History

Monk seal pair

Things you should know about the Hawaiian monk seal

Mom and pup on beach Foraging monk seal Mom and pup in water
  • The monk seal is known in Hawaiian as ʻīlio holo i ka uaua, which means "dog running in the rough seas", or nā mea hulu, which means "the furry one". Click here to learn about monk seals in Hawaiian culture.
  • Hawaiian monk seals are endemic to the Hawaiian Islands and Johnston Atoll, this means that they are native and are found nowhere else on earth.
  • The Hawaiian monk seal is one of only two mammals indigenous to Hawaii's terrestrial environment (the other is the hoary bat).
  • Hawaiian monk seals are one of the most endangered animal species in the world. Only about 1,100 seals are left and their overall population is in decline.
  • The Hawaiian monk seal is Hawaii's official state mammal.
  • The youngest females to give birth are 4-5 years old, though many begin pupping when older.
  • Maximum age is 30-35 years, but very few seals live this long.
  • Hawaiian monk seals usually dive for an average of 6 minutes when feeding; but they can hold their breath as long as 20 minutes.
  • Monk seals can dive as deep as 1,854 ft (565 meters)! But they usually make dives less than 200 ft (60 meters) to forage on the sea floor.
  • Monk seals usually sleep on the beaches of the Hawaiian Islands, sometimes for days at a time. They can also sometimes be seen sleeping underwater in small caves.
  • Monk seals do not migrate seasonally, but some seals have been tracked traveling hundreds of miles in the open ocean. Individual seals often frequent the same beaches over and over, but do not defend regular territories.
  • Hawaiian monk seals do not live in colonies like sea lions or elephant seals. They are mostly solitary but sometimes may be seen lying near each other in small groups - usually not touching.

Diet

Monk seals diet

Hawaiian monk seals are "generalist" feeders, which mean they eat a variety of foods depending on what's available. They eat many types of common fishes, squid, octopus, eels and crustaceans (crabs, shrimp and lobster). Diet studies indicate that they prefer prey that hide in the sand or under rocks, unlike most of the locally popular game fish, e.g. ulua, papio and ʻoʻio. The proportion and type of prey consumed varies significantly by island, year, age and sex. However, lobster has not been identified as a primary monk seal prey item.

Taxonomy

Monk seals are divided into 2 genera: Monachus or Mediterranean monk seal and Neomonachus or New World monk seals, which include the Hawaiian and Caribbean monk seals. This recent reclassification means that the endangered Hawaiian monk seal is the only surviving member of the Neomonachus genus.

Sleeping pair of monk seals
  • Hawaiian monk seal
    • Kingdom: Animalia
    • Phylum: Chordata
    • Class: Mammalia
    • Order: Carnivora
    • Family: Phocidae
    • Genus: Neomonachus
    • Species: schauinslandi

Physical Description

Monk seal anatomy
  • Adult monk seals are about 6-7 feet (1.8-2.1 meters) in length and weigh about 400-600 pounds (~180-270 kilograms).
  • Both male and female monk seals are similar in body length.
  • Monk seal pups are black, while adults are dark gray to brown on their back and light gray to yellowish brown on their belly.
  • Monk seals have a "catastrophic molt", where they shed the top layer of their skin and fur about once a year.
  • When seals spend a long time at sea foraging, they can grow algae on their fur. Seals that look green usually haven't molted recently and may be getting ready to shed into a silvery new coat.

How to tell seals apart

Most Hawaiian monk seals have unique natural markings, such as scars or natural bleach marks, which help identify individual seals. Some seals have identifiers that are applied by authorized NOAA Fisheries Service personnel that help to keep track of individual animals, such as bleach markings or flipper tags.


The only way to confirm whether a seal is female or male is by looking at its belly.

Male and female identification

For more information about the natural history of the Hawaiian monk seal: