Hawaiian Monk Seal

Neomonachus schauinslandi

Adult monk seals are generally light gray while pups are often black or dark gray. At maturity, this species reaches from 6 feet 11 inches to 7 feet 10 inches and weighs from 510 to 600 pounds.

Monk seal with virus at the Pieterburen Seal Sanctuary, Netherlands

© Greenpeace / Lorette Dorreboo

Estimated Population

1,300 – 1,400 seals occurring only in the Hawaiian Archipelago, listed as endangered under The Endangered Species Act.


Monk seals mainly occupy the uninhabited atolls of the Northwestern Hawaiian Islands; however, some have also been spotted around the Main Hawaiian Islands.

The monk seal depends largely on the coral reefs for feeding. Their diet consists of fish, eels, octopuses, and crustaceans.

Monk seals are very fast and efficient swimmers; they can travel long distances and dive over 800 feet.

After four years, females reach sexual maturity but do not bear young until age 6 or 7. Similar to other species of seal, monk seals only bear 1 young per year. Although 90 percent of pups survive to weaning, in recent years, survival of pups post-weaning has been as low as 30 percent in some areas. There were 8 pup deaths this year at the French Frigate Shoals.


Skewed male to female ratios due to low pup survival rates have led to groups of aggressive males attempting to mate with a single female and with pups resulting in mortal wounds.

Fishery-related deaths play a major role in low populations. Each year, around 10 monk seals wash ashore entangled in fishing nets, while others become entangled in marine debris, are disturbed at haul-out sites or become poisoned by contamination.

Natural threats such as shark predation, a decline in atoll productivity, intra-species aggression by large males, and a loss of pupping habitat likely due to sea-level rise also threaten monk seal populations. A natural catastrophe such as a disease outbreak could lead this species to extinction.

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