Hawaiian monk seals can grow up to 8 feet long, and weigh between 300-600 pounds. When they’re young, they have dark gray backs and light undersides. The adults have a gray coloring to them but tend to turn brown later in life due to weathering. 

They have prominent hind flippers that help them swim to depths of 500 m, as well as smaller front flippers. The thick skin folds around their neck are similar to that of a hood on a monk’s robe, hence their common name.

Hawaiian monk seals are endemic to Hawaii, and primarily live on the remote Northwestern Hawaiian Islands with a small population on the big island of Hawaii. They use coral reefs as foraging grounds but will come ashore to rest on beaches.

They are unique in that they prefer tropical environments. Most monk seals will spend ⅔ of their time at sea, primarily foraging and swimming.

Hawaiian monk seals are opportunistic predators and will hunt for their food in shallow reefs eating fish, octopuses, and crustaceans. They will also dive over 1,000 feet to capture prey!

These seals can be considered “benthic” foragers, which means they eat organisms from the bottom of the ocean, including crustaceans and eels.

Hawaiian monk seals reach sexual maturity around 5-6 years old but most won’t start breeding until they are around 6 or 7. Both sexes are polygamous and females will have a live birth of one pup onshore in the springtime. These pups will stay with the mother and nurse for about a month, and females will even foster the offspring of other monk seals.

Their name in Hawaiian is “ilio-holo-i-ka-uaua” which means “dog running in rough water”.

The Hawaiian monk seal is the state mammal of Hawaii, and also one of only two species that is endemic to Hawaii.

Hawaiian monk seals are aggressive in sexual acts and the males will often act violent towards females; an act called “mobbing”.