Hawaiian Monk Seal

Page - September 21, 2007

Hawaiian Monk Seal405

Estimated population:

13,000 - 14,000 seals occurring only in the Hawaiian Archipelago and is listed as an endangered species under The Endangered Species Act.

Ways to identify this species:

Adults 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 seals mainly occupy the uninhabited atolls of the Northwestern Hawaiian Islands; however, some have 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.