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Hawaiian Monk Seal (Monachus schauinslandi)

Range and Habitat: Hawaiian Archipelago, Johnston Atoll
Hawaiian Monk Seal
Hawaiian Monk Seals (Photo: National Marine Fisheries Service)

Status under U.S Law:

ESA- Endangered
MMPA - Depleted
Conservation issues: Insufficient prey for juveniles, marine debris, shark predation, adult male aggression, fishery interactions, introduced disease, climate change, human disturbance
Physical characteristics: At Birth Maturity
Length 1 m
2.1-2.4 m
Weight 16-18 kg
(35-40 lb)
170-205 kg
(375-450 lb)


25-30 years

Hawaiian monk seals are one of the world's most endangered seals. Numbering about 1,100 animals, they occur almost exclusively in the Hawaiian Archipelago (Figure 1). They are found primarily at six major colonies (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). Rare sightings have also been made at Johnston Atoll some 600 nautical miles south of Lisianski Island and are being found more and more frequently in the Main Hawaiian Islands (MHI). Hawaiian monk seals are one of only two remaining monk seal species and the only seals native to Hawaii.

The main Hawaiian Islands were undoubtedly an important part of the species’ range before the arrival of humans in the archipelago perhaps 800 to 1200 years ago; however, the dearth of historical records or accounts of seals suggests that they were extirpated from those islands shortly after the first Polynesian settlements were established. In the late 19th century, hunting in the NWHI pushed Hawaiian monk seals 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. However, since the 1990s monk seals have made significant progress towards reoccupying the MHI where their numbers have increased steadily to at least 175 seals. If current rates of decline in the NWHI and of increase in the MHI continue, monk seal numbers will to shrink until the mid-2020s at which time seals in the MHI will begin to outnumber those in the NWHI and the overall population size will begin to increase (Baker et al 2010).

The National Marine Fisheries Service, is the lead agency responsible for monk seal research and management in partnership with other agencies (e.g., the State of Hawaii Division of Aquatic Resources, Fish and Wildlife Service, Office of National Marine Sanctuaries, Coast Guard, and U.S. Navy), non-governmental groups (e.g., The Marine Mammal Center, the Hawaii Wildlife Fund, the Monk Seal Foundation, and the Marine Conservation Institute) and individuals and volunteers. The Service adopted a recovery plan for Hawaiian monk seals in 1982 that was updated in 2007. Critical habitat for monk seals was first designated in 1986 and expanded in 1988, with consideration of further expansion currently underway (see below).

Figure 1. 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 (Source: NOAA)

Most of the Hawaiian monk seal population lives within the Papahānaumokuākea Marine National Monument established in 2006. Despite decades of protection from human disturbance and other direct human impacts, monk seal numbers in the NWHI have continued to decline due to factors that include (1) starvation caused by declines in prey availability (possibly related to long-term changes in oceanographic and climate conditions and ecological disruption from past commercial fishing, (2) entanglement in marine debris, (3) predation by sharks, (4) attacks on pups and females by aggressive adult males, and (5) loss of pupping beaches due to rising sea level and other impacts of climate change.


The Hawaiian monk seal recovery program has been chronically underfunded (Lowry et al 2011). Despite major increases in program needs for research and management issues in the MHI, increasing logistical costs for work in the NWHI, and plans for expanding recovery measures over the last 20 years, overall agency funding remained essentially unchanged and annual funding requests specifically for monk seals have been inadequate. The agency's 2007 Hawaiian monk seal recovery plan projected a need for about $7.2 million per year to carry out identified tasks, but the agency currently requests about a third of that amount. The U.S. Congress has periodically provided funding above agency requests, most notably in Fiscal Years 2009 and 2010 when funding nearly doubled to $5.7 and $5.4 million. This allowed a significant but brief increase in field work in the NWHI and hiring of staff for management work in the MHI; however, in 2011 a 60 percent funding cut led to substantial cutbacks of the program. For 2012 and 2013 funding was increased by 30 percent over 2011 levels, but in 2014, it was again cut by 35 percent.

Monk Seals in the Northwestern Hawaiian Islands

Each year the National Marine Fisheries Service sends field teams to all or most of the major breeding sites to monitor seal abundance, survival, and pup production, and to mitigate factors impeding recovery. Among other things, teams disentangle seals caught in marine debris, mitigate shark predation, translocate pups from sites with low survival to sites with higher survival, intervene to deter attacks by aggressive male seals on other seals, 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, field camp scientists also have investigated ways of treating seals to control parasites that reduce the fitness of individual animals (see below). Together, these actions have slowed, but not reversed monk seal decline in the NWHI.

Due to funding cuts, field crews had to reduce time spent at most NWHI breeding atolls by 50 to 80 percent depending on the location in 2012 and 2013. As a result, it was not possible to develop reliable estimates of overall abundance of seals in the NWHI for those years and opportunities to rescue imperiled seals were greatly reduced. 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 increased at most sites, but was still below historic levels, in part because some camps had to be evacuated due to a hurricane threat. Results of work in 2014 were not available at the time of this update

Deworming: Monk seals, like all mammals, carry internal parasites such as tapeworms that absorb nutrients from food in the stomach and intestine and cause various ailments (e.g., gastrointestinal ulcers). Poor juvenile survival due to limited food availability has been identified as a major cause of the monk seal decline in the NWHI. In 2009, scientists began administering medication to reduce parasites in juvenile seals on Laysan Island in hopes of improving nutrient uptake to a point where it would improve their survival to breeding age (Gobush et al. 2011). In 2011 they began testing a new topical drug, Profender, that could be administered to seals as they slept on the beach. The new drug was initially field tested on 17 seals. It caused no ill effects and reduced or eliminated parasites in some, but not all of the seals treated.

In 2012 this new drug was applied to 53 juvenile seals at Laysan Island, Lisianski Island, and Kure Atoll to evaluate its effectiveness at improving juvenile survival rates with a larger sample. Scats from treated animals continued to show mixed results with regard to reducing parasites. Due reduced field seasons and limited opportunities to re-sight treated seals in 2012 and 2013, it has not yet been possible to fully assess whether application of the drug has improved the survival rates of treated seals. Nevertheless, because the drug has had no ill-effects on seals, is inexpensive, and has shown some efficacy, its use was continued on a limited basis in 2013 (i.e. on six juvenile seals in poor condition at three locations -- Kure Atoll, French Frigate Shoals, and Lisianski Island) pending further studies to test alternative dosage levels.

Shark Predation: In the mid-1990s shark predation on monk seal pups increased sharply at French Frigate Shoals. Nearly a third of all pups born at the atoll in 1996 were either known or suspected to have been killed by sharks (Harting 2010). Such predation is believed to have removed 207 of the 854 pups born at this atoll (24 percent) between 1997 and 2010. By comparison, pup deaths attributed to sharks at Laysan and Lisianski Islands over the same period amounted to just 2 percent (10 of 540) and 4 percent (13 of 334), respectively. Shark predation has remained substantially higher at French Frigate Shoals than at other NWHI sites, and preliminary monitoring results for 2013 indicate a third of all pups there (11 of 34 pups) were known or suspected to have died of shark attacks.

All observed shark attacks at French Frigate Shoals since 1997 have been by Galapagos sharks. It is believed that a small number of sharks have learned to patrol atoll pupping beaches to catch unwary pups. To reduce such deaths, the Service has moved newly weaned pups to other islets at the atoll where shark predation is less common. In 2010 and 2011, all pups surviving to weaning (i.e., 17 and 15 pups, respectively) were moved to areas of low shark predation and all were alive when the field team left at the end of their respective field seasons. In 2013, 13 weaned pups were moved to areas of low shark predation. Although the Service has also considered moving mother and pup pairs before pups are weaned, it is believed doing so would pose too great a risk of disrupting the mother-pup bond essential for the pup’s survival.

To further mitigate shark predation the Service has been attempting to catch and kill Galapagos sharks within a few hundred yards of pupping sites using closely tended baited hooks. When other species of sharks are caught, they are released alive whenever possible. Efforts to catch sharks began in 2000, but have achieved limited success since sharks quickly learned to avoid people and boats. Between 2000 and 2007 field personnel killed 12 Galapagos sharks.

The approach of catching and killing sharks has been controversial and resource managers at the Papahānaumokuākea Marine National Monument, who are responsible for protecting all marine species in the NWHI, have been reluctant to grant permits to kill marine predators in the Monument. Therefore, in 2008 and 2009 the Service suspended efforts to catch sharks while it tested various shark deterrents (Gorbush and Farry 2010). At the same time, the NWHI Coral Reef Ecosystem Reserve (a part of the Office of National Marine Sanctuaries that also serves as a Monument co-manager) funded studies of shark movement at French Frigate Shoals. Deterrent methods proved to be ineffective, but shark tagging studies confirmed that only about 20-30 of the estimated 600 Galapagos sharks at the atoll patrolled waters near monk seal pupping beaches. Therefore, in 2010, the Service renewed efforts to catch sharks near pupping beaches using new methods, including short drum-lines, five-hook bottom-sets, hand lines, and a spring-loaded net set along the beach. The sharks remained elusive however and only two Galapagos sharks were caught between 2010 and 2013. The effort is being continued in 2014.

Translocations: In the late 1980s the survival of seals less than three years old began to decrease. Although a variety of factors affect juvenile survival, an increase in underweight and starving pups and juveniles with no evidence of disease indicates that reduced in prey availability is a significant factor in their survival, particularly at French Frigate Shoals. Therefore, in the 1980s and early 1990s, scientists and managers brought under-nourished pups and juveniles principally from French Frigate Shoals into captivity to restore them to good condition and then return them to the wild in the NWHI. While successful, it was expensive and exposed the seals to various additional risks. In the mid-1990s, 10 of 12 seals brought into captivity developed an eye ailment that led to blindness and caused the Service to halt this program.

In recent years, juvenile survival has increased at some islands, particularly Laysan and Lisianski, suggesting that prey resources at those locations had improved. Increasing seal counts and good body condition of animals at Nihoa Island have also indicated favorable prey conditions for juvenile survival at that location. To take advantage of these more favorable conditions, scientists began moving newly weaned pups from French Frigate shoals to other subpopulations where prey resources appeared more conducive to juvenile survival. In each of 2008 and 2009, they moved six weaned pups from French Frigate Shoals to Nihoa, and in 2012 and 2013, two and six weaned pups, respectively, were moved from French Frigate Shoals to Laysan Island. The success of those efforts has been difficult to assess because of the impact of shortened field seasons in reducing opportunities for resighting seals and estimating survival rates. Translocations were significantly increased in 2014 under a new permit to enhance recovery efforts. Thirteen weaned pups from French Frigate Shoals, Midway, and Kure were moved to Laysan and Lisianski and fitted with satellite transmitters to track their movements and help assess their survival rates. For comparative purposes eight young seals born at Laysan, Lisianski, and Midway were also fitted with satellite transmitters.

Entanglement in Marine Debris: Since 1982, National Marine Fisheries Service field teams have documented 319 entangled seals on NWHI and MHI beaches (Figure 2). They are caught in netting and line that drifts into the NWHI from fishing grounds in southeastern Asia and Alaska. Of those, 214 were disentangled by field teams, 89 freed themselves, 8 died, and the fate of 8 others was not determined. The number of seals that drown at sea or die of wounds and abrasions when biologists are not present is unknown. Most entangled seals are juveniles. A large majority of known entanglements have occurred in the NWHI. In 2013, when 8 entanglements were documented, seven were found in the NWHI and only one was in the MHI. In 2012 and 2013, recorded entanglement numbers declined; but this is likely due to shortened field seasons in the NWHI. In 2013, field teams rescued and released five entangled monk seals, while three were able to free themselves. No entanglement deaths were recorded in 2013.

Number of Hawaiian monk seals observed entangled from 1992 through 2013.

Figure 2. Number of Hawaiian monk seals observed entangled from 1992 through 2013. Large Points for 2012 and 2013 are years with significantly reduced field effort compared to earlier years. (Data provided by the National Marine Fisheries Service, Pacific Islands Fisheries Science Center)

In addition to disentangling animals, field crews have been removing hazardous debris from NWHI beaches since the early 1980s. In the late 1990s work also began to remove net debris from coral outcrops in NWHI lagoons. Clean up work is now coordinated by the Service's Coral Reef Ecosystem Division, but also involves the Office of National Marine Sanctuaries, the Coast Guard, the Fish and Wildlife Service, the State of Hawaii, and non-governmental groups and volunteers. More than 700 metric tons of netting and other debris have been removed since work began. This has undoubtedly prevented the death and injury of many monk seals, as well as sea turtles, seabirds, fish, crabs, and corals. Most recently, in 2013 efforts funded by the National Oceanic and Atmospheric Administration's Marine Debris Program were focused at Midway Atoll where 13 tons of netting and other debris were removed from the atoll's shoreline and lagoon.

Hawaiian 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 notable bright spot for the species recovery, 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.

Main Hawaiian Island 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. In 2013 researchers conducted two surveys at Niihau in cooperation with local residents, yielding counts of 43 and 69 seals including at least 19 pups-the highest counts for that island to date. Another survey for Niihau was scheduled for late in 2014. Funding was insufficient for MHI-wide surveys in 2013 and 2014, but based on the number of individually identified seals recorded by Service scientists and volunteers in 2013, the estimate of the minimum number of seals in the MHI was increased from 150 to 175 seals. This includes 31 individual seals (19 pups and 12 older seals) seen only on Niihau. The MHI population is believed to be growing at a rate of five to seven percent per year and at least 40 pups (including the 19 pups at Niihau) were born there in 2013. Seven deaths were also documented, but only one - the above noted seal that died after ingesting a fish hook - was clearly human-related.

Interactions with Nearshore Fishing: In the MHI, monk seals can be injured or killed by hooks when taking bait or fish from the lines of near shore fishermen. In 2013, 13 seals were seen carrying hooks or fishing lures, five of which were removed after the seals were captured. The other 8 seals were able to shed the hooks themselves. One seal that was first seen with line extending from its mouth in 2012 died in 2013. After being resighted in poor condition on the Island of Hawaii, it was captured for treatment but died while being examined. The examination and subsequent necropsy revealed that a hook had perforated its trachea and esophagus. This caused extensive buildup of scar tissue and restricted airflow in the area.

Also in 2013, a seal was found injured with a three pronged fishing spear embedded in the skin on the top of its head. The spear, which had not punctured the skull, was removed by a seal rescue team and the seal survived. Monk seals sometimes attempt to take speared fish off of spears or strings of caught fish. Although such interactions pose no risk of hooking injury, they can cause animosity toward seals among people who incorrectly assume seals must normally prey on such fish and are therefore in direct competition with fishermen. In addition, such interactions can reinforce seal behavior of approaching humans (including other fishermen) to obtain food. Such behavioral reinforcement can increase the chances of seals getting hooked or becoming nuisance animals that threaten swimmers and divers.

New Monk Seal Health Care Facility: In 2014, The Marine Mammal Center of Sausalito, California, a non-profit veterinary research center and rehabilitation facility for injured and distressed marine mammals, opened a new health care center for monk seals. Located on land owned by Natural Energy Laboratory Hawaii Authority in Kailua-Kona on the Island of Hawaii, the $3.2 million facility was funded entirely with private donations raised by the Center. Named Ke Kai Ola, meaning "healing sea," the new monk seal hospital features holding pools able to maintain up to 10 seals, pens to hold seals in isolation when needed, a medical building with a laboratory and food preparation area, and an open-air education pavilion for visitors.

Although its official opening was on 2 September 2014, Ke Kai Ola received its first patients in early July: four under-nourished monk seals brought in from the NWHI by the National Marine Fisheries Service. The four seals included two yearlings, one from Midway and one from French Frigate Shoals, and two weaned pups from Pearl and Hermes Reef. All four were successfully nursed back to health and fattened before being returned and released to the NWHI by the Service in early September 2014.

Expansion of Hawaiian Monk Seal Critical Habitat

Section 4(b)(2) of the Endangered Species Act requires the designation of “critical habitat” for species, such as Hawaiian monk seals, listed as endangered. Critical habitat designations must identify physical or biological features essential to seals as well as any special management considerations. In 1986 the Service designated all beaches and near shore waters out to the 10-fathom isobath around all NWHIs except the Midway Islands as critical habitat for monk seals. In 1988, those boundaries were extended to the 20-fathom contour. Since then, information on the species’ ecology and the growth of the MHI seal population indicate that other areas are essential to the species' survival (53 Fed. Reg. 18988). In light of this information, several environmental groups petitioned the Service in July 2008 to designate additional areas as critical habitat in both the NWHI and the MHI.

In response, the Service published a proposed rule on 2 June 2011 (76 Fed. Reg. 32026) to expand monk seal critical habitat boundaries to all beaches and waters in the NWHI within the 500 m isobath with the exception of a protected harbor on the Midway Islands, and to most shoreline areas and waters in the MHI from a point 5 m above the high tide line (generally reflecting the line of vegetation or debris) out to a depth of 500 m. The MHI proposal excluded developed harbors, shorelines of certain military facilities, and shorelines armored with bulkheads or rock rip-rap. Together, proposed areas in the NWHI and MHI would cover more than 28,500 km2 (11,000 mi2) and most areas where monk seals occur.

The Service noted that the proposed areas include six types of physical and biological features essential to monk seals: (1) beaches preferred for pupping and nursing, (2) shoreline areas for haul-out, resting, and molting, (3) coastal areas with low levels of human disturbance, (4) shallow sheltered areas adjacent to pupping and nursing areas, (5) marine areas with adequate prey quality and quantity, and (6) foraging areas from 0 to 500 m deep. The Service also noted that those features could be affected by: (1) in-water and coastal construction, (2) dredging and disposal of dredged material, (3) energy development, (4) activities that generate water pollution, (5) aquaculture, (6) fisheries, (7) vessel groundings and projects posing oil spill risks, and (8) military exercises.

On 5 August 2011, the Commission commented on the proposed rule noting that the proposed designation was an appropriate, proactive step that was in keeping with the species critical status and the need to ensure its protection. The Commission therefore recommended that the proposed rule be adopted as written. The proposal elicited considerable controversy from many reviewers who considered the size of the proposed area excessive. In light of the comments it received, the Service announced on 25 June 2012 (77 Fed. Reg. 37867) that it was delaying a final decision to further consider concerns expressed about the sufficiency and accuracy of data and analyses used to evaluate the proposed boundaries. A final decision had not yet been announced as of this update.

Enhancing Hawaiian Monk Seal Recovery Prospects

In August 2011 the Service requested comments on a draft programmatic environmental impact statement analyzing several new research and management initiatives to enhance monk seal recovery. Principal among the initiatives considered in the draft statement were (1) conducting a two-stage translocations to temporally move weaned pups from areas with low survival to areas with higher survival, and then back to their natal sites once they reach the age of 3; (2) monitoring seals for infectious diseases and developing vaccination protocols for two vectors of particular concern for monk seals (i.e., West Nile virus and morbillivirus); (3) testing and, as warranted, expanding deworming treatments to reduce parasite loads in juvenile monk seal digestive tracts; (4) testing and, as appropriate, using new methods to modify monk seal behavior patterns that place them at risk from interactions with people and fishing gear in the MHI; and (5) testing and, as appropriate, using drugs on male seals to reduce aggressive behavior toward pups, juveniles, and adult females. As part of that effort, the Service applied to its permit office for an enhancement permit to authorize such activities under the Endangered Species Act and the Marine Mammal Protection Act.

The two-stage translocation proved to be highly controversial. The Service considered the MHI to be the most effective temporary receiving site for NWHI juvenile seals because it was the area where the highest juvenile survival had consistently been observed.  However, some fishermen and Native Hawaiians in the MHI were concerned that moving seals to the MHI would increase seal predation on fish stocks.

On 24 October 2011 the Commission wrote to the Service commending the agency for its comprehensive evaluation of new or expanded recovery actions. Studies of monk seal diet in both the NWHI and MHI had revealed there was very little overlap between monk seal prey and the sizes and species of fish and shellfish caught by fishermen, and the Commission therefore recommended that the Service move forward with the proposed two-stage translocation work as quickly as possible. It also recommended that the agency (1) consider alternative ecosystem-based management measures (e.g., enhancing monk seal prey habitat) to enhance juvenile survival in the NWHI; and (2) give high priority to further testing of a morbillivirus vaccine on captive monk seals to identify possible side effects of the vaccine on seals.

In April 2014 the Service released a final environmental impact statement and the following June it issued a final record of decision on its selected options and an associated research permit. In view of opposition to moving seals from the NWHI to the MHI, the agency decided to select a limited two-stage translocation approach in which it could move weaned pups from areas of low juvenile survival to areas of high survival within the NWHI, within the MHI, or from the MHI to the NWHI, but not from the NWHI to the MHI. All other options were approved as initially proposed. Plans for implementing some of the new measures have been developed and implementation began later in 2014 with vaccine testing, vaccination program planning, and multiple translocations.

Links for Additional Information

Commission Reports and Related Publications:

See Hawaiian Monk Seal sections chapters on Species of Special Concern in past Annual Reports to Congress
(Link to Past MMC Annual Reports)

2011 Lowry et al 2011. Recovery of the Hawaiian monk seal

2007 Endangered, Threatened, and Depleted Marine Mammals in U.S. Waters - A Review of Species Classification Systems and Listed Species

2007 The Status of Protection Programs for Endangered, Threatened, and Depleted Marine Mammals in U.S. waters

2002 Workshop on Management of Hawaiian Monk Seals on Beaches in the Main Hawaiian Islands
Commission Letters:

To view recent Commission letters concerning Hawaiian Monk Seals choose a date below

April 17, 2013 on a Hawaiian monk seal research permit

September 3, 2013 on a Hawaiian monk seal research permit

December 15, 2011 on a Hawaiian monk seal research permit

November 17, 2011 on NMFS funding for monk seal recovery

October 24, 2011 on proposed activities to enhance monk seal recovery

August 5, 2011 on proposed rules to expand monk seal critical habitat

June 6, 2011 on a Hawaiian monk seal research permit

February 23, 2011 on a Hawaiian monk seal research permit
Additional Links:

National Marine Fisheries Service Stock Assessment Reports

National Marine Fisheries Service - Pacific Islands - Hawaiian Monk Seal






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