Marine Mammal Commission

Hawaiian Monk Seal

The Hawaiian monk seal is the most endangered pinniped in U.S. waters and one of the most endangered seals worldwide. Most Hawaiian monk seals live in the remote Northwestern Hawaiian Islands where their numbers have been declining since the 1950s. Since the 1990s, however, a small population in the Main Hawaiian islands has increased significantly in size and now represents one of the brightest hopes for reversing the long-term decline.

The name monk seal is believed to come from folds of skin around the neck that were thought to resemble the cowl of a monk’s hood. The Hawaiian name for the monk seal is Ilio-holo-i-ka-uaua, meaning dog running in the rough seas. Monk seals feed primarily on a wide array of small fishes, squids, octopuses, and crustaceans, found on the sea floor on sand flats, outer reef slopes, offshore banks and coral reefs. Most dives are to 60 meters or less, although some seals have been recorded diving to depths of more than 500 meters.

Hawaiian monk seal on rocky beach.

Monk seal on rocky beach in the French Frigate Shoals, NWHI. (Brenda Becker, NOAA)

Species Status

Only about 1,100 Hawaiian monk seals survive today (2015 stock assessment report). They occur almost exclusively in the Hawaiian Archipelago, with occasional sightings at Johnston Atoll. Most monk seals are found at eight primary sites: Necker Island, Nihoa Island, French Frigate Shoals, Laysan Island, Lisianski Island, Pearl and Hermes Reef, the Midway Islands, and Kure Atoll) in the remote, largely uninhabited atolls of the Northwestern Hawaiian Islands (NWHI). All of these islands are now part of the Papahānaumokuākea Marine National Monument. Along with the Mediterranean monk seal, the Hawaiian species is one of only two remaining monk seal species.

The Hawaiian Islands archipelago showing major Hawaiian monk seal breeding locations in the Northwestern Hawaiian Islands and the boundary of the Papahānaumokuākea Marine National Monument. (NOAA)

The Hawaiian Islands archipelago showing major Hawaiian monk seal breeding locations in the Northwestern Hawaiian Islands and the boundary of the Papahānaumokuākea Marine National Monument. (NOAA)

Hawaiian monk seals were apparently eliminated from the Main Hawaiian Islands (MHI) shortly after the first Polynesians arrived. In the late 19th century, hunting in the NWHI pushed the species to the brink of extinction. Their numbers may have increased in the NWHI during the early 1900s, but they have been declining at a rate of 3 to 4 percent per year since at least the 1950s. Since the 1990s, however, monk seals have made significant progress towards reoccupying the Main Hawaiian Islands (MHI) where their numbers have increased steadily to at least 185 seals by 2015. An analysis based on 2008 data on declining population trends in the NWHI and increasing trends in the MHI projected that monk seals in the MHI would outnumber those in the NWHI as early as the mid 2020s (Baker et al. 2011a). However, because it appears that the decline in the NWHI and the increase in the MHI have both slowed, whether or when monk seal abundance in the two regions might equalize is uncertain.

Threats to the species differ substantially between the NWHI (where they are now well protected from human interactions but continue to decline), and the MHI (where human related impacts pose a significant and growing challenge) (Baker et al. 2001b). In the NWHI, the major treats now include entanglement in marine debris (particularly derelict fishing gear), starvation due to limited prey, shark predation, attacks on pups and females by aggressive adult male seals, and loss of pupping beaches due to rising sea levels. In the MHI, threats include disturbance and interactions with people and their pets on haul out beaches, hookings by fishermen, entanglement in fishing gear, introduced diseases, pollution, and intentional killing by people.

The National Marine Fisheries Service (NMFS) is the lead agency responsible for monk seal research and monk seal management but it relies heavily on partnerships with other agencies (e.g., the State of Hawaii Division of Aquatic Resources, U.S. Fish and Wildlife Service, Office of National Marine Sanctuaries, U.S. Coast Guard, and U.S. Navy), non-governmental groups (e.g., the Marine Mammal Center, the Hawaii Wildlife Fund, the Monk Seal Foundation, the Marine Conservation Institute), and individuals and volunteers. NMFS adopted a recovery plan for Hawaiian monk seals in 1982 that was updated in 2007, and designated critical habitat in 1994.

In January 2016, NMFS released a new Hawaiian Islands Monk Seal Management Plan. The management plan is an important step toward successfully managing the MHI monk seal population, preparing to address emerging challenges, and fostering co-existence between humans and seals.

More Information

Threats to Hawaiian Monk Seals

Monk Seal Health Care Facilities

Expansion of Hawaiian Monk Seal Critical Habitat

Enhancing Hawaiian Monk Seal Recovery Prospects

What the Commission Is Doing

We have participated on or attended meetings of the NMFS Hawaiian monk seal recovery team and have also periodically convened Hawaiian monk seal program reviews to provide advice on priority research and management needs. We have also provided funding support for various research and management actions.

Commission Reports and Publications

See Hawaiian Monk Seal sections in chapters on Species of Special Concern in past Annual Reports to Congress.

Lowry, Lloyd F., Laist, David W., Gilmartin, William G, and Antonelis, George A. 2011. Recovery of the Hawaiian monk seal: a review of conservation efforts, 1972 to 2010, and thoughts for the future

2002. Final Report: Workshop on Management of Hawaiian Monk Seals on Beaches in the Main Hawaiian Islands

Reports prepared for the Marine Mammal Commission:

Lowry, Lloyd, Laist, David W., and Taylor, Elizabeth. 2007. Endangered, Threatened, and Depleted Marine Mammals in U.S. Waters – A Review of Species Classification Systems and Listed Species

Weber, Michael L. and Laist, David W. 2007. The Status of Protection Programs for Endangered, Threatened, and Depleted Marine Mammals in U.S. waters

Commission Letters

Letter Date Letter Description
November 17, 2011

Letter to NMFS on funding for monk seal recovery

October 24, 2011

Letter to NMFS on proposed activities to enhance monk seal recovery

August 5, 2011

Letter to NMFS on proposed rules to expand monk seal critical habitat

Learn More

Current Conservation Efforts

Monk Seals in the Northwestern Hawaiian Islands

Each year, NMFS’ Pacific Islands Fisheries Science Center sends field teams to all or most of the major breeding sites in the NWHI to monitor seal abundance, survival, and pup production, and to mitigate factors likely to cause monk seal deaths. Among other things, teams disentangle seals caught in marine debris, mitigate shark predation, move pups from sites with low survival to sites with higher survival, intervene to deter attacks by aggressive male seals on other seals, provide captive care to undersized pups and juveniles, and treat seals for injuries. A recent analysis found that between 17 and 24 percent of all seals alive in the NWHI in 2012 had either benefited directly from such interventions or were descendents of seals that had benefited from such interventions between 1980 and 2012 (Harting et al. 2014). In recent years, scientists also have investigated ways of treating seals to control parasites that reduce the fitness of individual animals. Together, these actions have slowed, but not reversed monk seal decline in the NWHI.

Reductions in funding levels have required field crews to reduce time spent at various NWHI breeding atolls by 50 to 80 percent. In 2014, for the third year a row, field work was limited, resulting in reduced opportunities to rescue seals and less reliable population estimates. While field teams intervened on 66 occasions to improve the survival chances of individual seals in 2011, they had only 21 and 33 opportunities to do so during the shortened field seasons in 2012 and 2013, respectively. In 2014, field time at most sites, was comparable to recent year and still below historic levels.  Field effort was also limited because some camps had to be evacuated due to a hurricane threat.

Monk Seals in the Main Hawaiian Islands

Hawaiian monk seal numbers in the MHI have been increasing steadily since the 1990s. While this has been a bright spot for the species status, it has raised many new and difficult research and management challenges, including the mitigation of interactions between seals and beachgoers, swimmers, and divers, and disease transmission to Hawaiian monk seals from domestic and feral animals. For example, during 2014, staff had to spend considerable time responding to reports of a juvenile female seal that had become a threat to human safety after people had socialized the animal by petting it and encouraging interactions with people. The seal had to be captured and translocated to the NWHI because of its modified behavior. The ability of NMFS staff to address the growing frequency of interactions with people has been limited based on available funds.

Main Hawaiian Islands Population Size

In many respects assessing and monitoring seals in the MHI is more difficult than in the NWHI. Seals are widespread around the islands and often occur in areas where researchers have very limited access, particularly on the privately owned Island of Niihau and nearby Lehua Rock. In 2014, for the second year in a row, researchers conducted surveys at Niihau in cooperation with local residents. The survey yielded a count of 63 seals including at least 20 pups, which was similar to the 2013 count. Most of those seals have not been seen elsewhere in the MHI. Funding was insufficient for MHI-wide, but based on the number of individually identified seals recorded in 2014, at least monk seals were known to be alive in the MHI that year, with at least 35 births. The MHI population is believed to be growing at a rate of about five percent per year. There were also 15 deaths documented in 2014, including one suspected deliberate killing, one due to an ingested hook, one due to a dog attack, and one due to infection by a pathogen (toxoplasmosis).

Additional Resources

NMFS – 2014 Hawaiian Seal Stock Assessment Report

NMFS – Hawaiian Islands Monk Seal Management Plan

NMFS – Pacific Islands Regional Office: Hawaiian Monk Seals

NMFS – Pacific Islands Fisheries Science Center: Hawaiian Monk Seal Research

U.S. Fish and Wildlife Service – Pacific Islands Office: Hawaiian Monk Seals

Marine Conservation Institute – Human Interactions with Hawaiian Monk Seals

Hawaiian Monk Seal Research Program on Facebook