Hawaiian monk seals are endemic to the Hawaiian Archipelago and are found primarily in the tropical waters of the northwestern Hawaiian island chain. Reproductive sites include Kure atoll, Midway atoll, Pearl and Hermes Reef, Lisianski Island, and French frigate shoals. Small populations also occur on Necker and Nihoa and breeding populations have been found on the main Hawaiian islands, also known as the windward Hawaiian Islands (Baker and Johannos, 2004; Antonelis et al., 2003).

Biogeographic Regions: pacific ocean (Native )

Other Geographic Terms: island endemic

endemic to a single state or province

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: This species occurs in the Hawaiian Islands. The six main reproductive sites in the northwestern Hawaiian Islands are Kure Atoll, Midway Islands, Pearl and Hermes Reef, Lisianski Island, Laysan Island, and French Frigate Shoals (NMFS 2007). Smaller breeding subpopulations occur on Necker Island and Nihoa Island, and monk seals have been observed at Gardner Pinnacles and Maro Reef. (NMFS 2007). Monk seals are now also found throughout the main Hawaiian Islands, where births have been documented on most of the major islands (Baker and Johanos 2004). Additional sightings and at least one birth have occurred at Johnston Atoll (NMFS 2007).

Hawaiian monk seals exhibit sexual dimorphism, with females being larger than males. Females have an average length of 2.25 m and an average weight of 203 kg. Males have an average length of 2.1 m and an average weight of 169 kg. After birth, Hawaiian monk seals are covered in black lunago (fetal hair), which they molt upon weaning. As juveniles, they are silvery gray, with darker hair on their dorsal side and white hair on their ventral side (National Marine Fisheries Service, 2007). Adults have brown pelage that is slightly gray on their backs and gradually fades to yellow and then white near the ventral surface of the animal. They have broad, flat, and moderately small heads with large black eyes. Unlike other pinnipeds, their nostrils are located on top of their short snout.

Range mass: 169 to 203 kg.

Range length: 2.1 to 2.25 m.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: female larger

Length: 215 cm

Weight: 170000 grams

No other native pinnipeds occur in the range of this species. Differs from the California sea lion, which could occur as an escape, in much shorter limbs, hind limbs that cannot be turned forward or used effectively for terrestrial locomotion, and absence of external ear pinnae.

• Terrestrial
• Marine

Hawaiian monk seals utilize terrestrial and marine habitats. Sandy beaches are used for parturition, nursing, molting, and resting. The most common parturition sites are on sandy beaches with exposed protective reefs, which limit shark access and provide shelter from large surf (Atonelis et al., 2003). Hawaiian monk seals use protected waters to teach weaned pups to capture prey. They use vegetation along the beach perimeter to protect themselves from ultraviolet rays, wind, and rain, and may also use terrestrial vegetation as shelter while they sleep (Gilmartin, 1983). Hawaiian monk seals spend the majority of their time in the ocean resting, interacting with each other, and foraging. They spend much of their time at depths of about 100 m and less, although some have been observed foraging at depths of over 300 meters (Parish et al., 2002).

Range depth: 300 (high) m.

Average depth: 100 m.

Habitat Regions: tropical ; terrestrial ; saltwater or marine

Aquatic Biomes: reef

Habitat Type: Marine

Comments: This seal occurs mainly in waters around islands, but it is also known to travel long distances in the open ocean. Often it is found around submerged reefs and atolls, or on sandy beaches; rocky ledges or gravel beaches sometimes are used as haulouts.

Birthing sites usually are on coral sand beaches backed by Scaevola shrubs, into which a female may take her pup for shelter at night. Births also occur on beaches lacking shrub cover and on rocky beaches (Necker Island). Primary features of pupping locations are very shallow water adjacent to the shoreline (may protect against shark attack) (Westlake and Gilmartin 1990) and stable substrate (Reeves et al. 1992). Human activity may cause females to shift to less favorable sites. Mating presumably occurs in the water.

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

One tagged pup traveled from Laysan Island to Johnston Atoll, 1,013 kilometers distant, within a period of less than 5 months (Reeves et al. 1992)

Hawaiian monk seals primarily prey upon teleost fishes, which make up roughly 80% of their diet. They appear to prefer fish belonging to the families Muranidae (marine eels), Labridae (wrasses), Holocentridae (squirrelfishes and soldierfishes), Balistidae (triggerfishes) and Scaridae (parrotfishes). Except for the beardfish family (Polymixiidae), which consists of deep sea benthic fishes, all fishes consumed by Hawaiian monk seals are shallow reef fishes (Goodman-Lowe, 1998). The remainder of the their diet consists of cephalopods and crustaceans, with the majority of consumed cephalopods being octopi. Hawaiian monk seals prey upon diurnal and nocturnal species of teleosts and cephalopods; however, juveniles tend to prey more heavily on nocturnal species (Goodman-Lowe, 1998). They primarily forage in shallow reefs (less than 100 m) near their natal atoll and foraging takes place near or at the sea floor. Individuals foraging in precious coral beds (Corallium rubrum) at depths of over 300 m have been recorded, where prey-capture rates may be higher (Parrish et al., 2002).

Animal Foods: fish; mollusks; aquatic crustaceans

Primary Diet: carnivore (Piscivore , Molluscivore )

Comments: When near breeding and resting beaches, monk seals forage benthically and feed on fishes and invertebrates both within atoll lagoons and in deeper water up to at least 500 meters (see NMFS 2007); diet includes wide variety of fishes, cephalopods, and crustaceans..

Hawaiian monk seals prey upon 40 species of marine animals that live in the coral reef ecosystem, including many species of teleost fish, cephalopods, and crustaceans.

The main predator of Hawaiian monk seals is the tiger shark (Galeocerdo cuvier), and shark predation is believed to be a significant contributing factor to pup mortality. Although male Hawaiian monk seals are known to commit infanticide, sharks are thought to be the main threat to pup survival. Seals avoid potential predators by nesting on beaches protected by exposed reefs and by feeding and resting in underwater reef caves.

Known Predators:

• Tiger Shark (Galeocerdo cuvier)

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 1 - 5

Comments: This species is represented by a single metapopulation (NMFS 2007). The different subpopulations exhibit varying degrees of demographic independence, with some having considerable levels of independence and other areas having higher degrees of subpopulation interaction (NMFS 2007)

250 - 1000 individuals

Comments: Current (2006) population size is approximately 1,200 (NMFS 2007), but not all of these are mature individuals.

This species is generally solitary on land and in the sea; groups may gather on favored beaches.

Shark predation is an important mortality factor. See Kenyon (1981) for a review of mortality factors such as sharks, entanglement in fishing gear, disease. Injuries sustained from adult males apparently contribute significantly to mortality in adult females (Hiruki et al. 1993).

Hawaiian monk seals communicate using vocalizations, including those between mothers and nursing pups.

Communication Channels: acoustic

Perception Channels: acoustic

Hawaiian monk seals live for 25 to 30 years in the wild. The lifespan of captive individuals is unknown.

Average lifespan

Status: wild: 25 years.

Average lifespan

Status: wild: 30.0 years.

Copulation in Hawaiian monk seals is rarely observed but usually takes place about 1 to 5 km off shore. Although little is known about the reproductive success or the mating system used by these animals, sexual dimorphism in conjunction with open water mating suggests polygyny (Weckerly, 1998). As in other pinnipeds, males likely mount females by biting their backs and grasping them with their foreflippers (Antonelis et al., 2003).

Mating System: polygynous

Hawaiian monk seals are monestrous and give birth to a single pup each year during an extended birthing season, which begins in March, peaks in April, and ends in August (Boness et al., 1998). Females leave the ocean to give birth on beaches close to their most recent breeding site. Birthing takes place after an 11-month gestation period, which contains a 3-month period of delayed implantation. Females are solely responsible for rearing offspring, which takes about 40 days. While rearing their pups, females fast and may lose hundreds of pounds. Pups weigh between 14 and 17 kg at birth and between 50 and 100 kg at weaning (National Marine Fisheries Service, 2007). Females wean pups by suddenly abandoning them and returning to the ocean, after which they wait 3 to 4 weeks before mating again (Boness et al., 1998). Hawaiian monk seals are one of three pinniped species that commonly foster pups, the other two being grey seals (Halichoerus grypus) and northern elephant seals (Mirounga angustirostris; Boness et al., 1998). Both genders reach sexual maturity between the ages of 5 and 10 years old. Pups weaned at higher weights generally have a greater chance of survival and become sexually mature at an earlier age.

Breeding interval: Hawaiian monk seals breed once yearly

Breeding season: February to March

Average number of offspring: 1.

Average gestation period: 11 months.

Range birth mass: 14 to 17 kg.

Range weaning age: 5 to 6 weeks.

Range age at sexual or reproductive maturity (female): 5 to 10 years.

Range age at sexual or reproductive maturity (male): 5 (low) years.

Average age at sexual or reproductive maturity (male): 10 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); delayed implantation

Average gestation period: 335 days.

Average number of offspring: 1.

Females are the only sex that invest in pup development. Pup fostering, which only occurs in 2 other pinniped species (gray seals, Halichoerus grypus and northern elephant seals, Mirounga angustirostris), takes place when females rear their young in close proximity to one another and may occur when pups are separated from their mothers. Most females tolerate nursing attempts by orphaned pups. Although pup fostering appears to result in little to no reward for adopting mothers, fostered pups clearly benefit from their foster mother's care (Boness et al., 1998).

Parental Investment: female parental care ; pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)

Polygynous. Pupping season is long, late December to mid-August; births occur mainly March-June, with a peak in May (Westlake and Gilmartin 1990). Gestation lasts about 1 year. In one study, about 1/3 of the females bred in consecutive years. Mother stays with pup during 5-6 week nursing period. Pups generally stay ashore until weaned. Relatively low reproductive rate; females are sexually mature at 5-9 years, and only 60-70% of the adult females give birth in a given year (Reeves et al. 1992). Few live beyond 20-25 years.

Hawaiian monk seals have been on the United States Fish and Wildlife Service’s endangered species list since November 23, 1976 and are listed as critically endangered on the IUCN Red List of Threatened Species. They have been in decline for over 20 years, and as of 2007, only 1200 individuals remained in the wild. Experts estimate that fewer than 1000 individuals will remain in the wild by the end of 2012. Efforts by the National Marine Fisheries Service to stabilize population numbers include keeping tourists away from known reproductive sites, moving aggressive males to new breeding grounds, and implementing a captive care program, which provides females with nutritional supplements. The goal of the captive care program is to increase the survival rate of female juvenile seals, which have an extremely low survival rate. Hawaiian monk seals are vulnerable to introduced disease, inbreeding depression, low genetic diversity, human disturbance, and competition with fisheries. In addition to the U.S. Fish and Wildlife Service’s Endangered Species Act, they are also protected under the Marine Mammal Protection Act.

Hawaiian monk seals are intolerant of human disturbance on beaches used for birthing and resting, and pup mortality is often higher at disturbed sites. Hawaiian monk seals began declining in the mid to late 1800’s, when they were hunted for their meat and skins. Currently, populations are declining due to over fishing and seals becoming hooked or entangled in fishing gear (Antonelis et al., 2003).

US Federal List: endangered

CITES: appendix i

State of Michigan List: no special status

IUCN Red List of Threatened Species: critically endangered

United States

Rounded National Status Rank: N2 - Imperiled

Rounded Global Status Rank: G2 - Imperiled

Reasons: Small range in Hawaiian Islands; small number of major pupping sites; low declining numbers of breeding females, despite intensive management in recent decades, threatened by very low survival of juveniles and subadults due to starvation (believed to be principally related to food limitation), entanglement of seals in marine debris, and predation; human interactions in the main Hawaiian Islands, including recreational fishery interactions, mother-pup disturbance on popular beaches, and exposure to disease, are negatively affecting the population.

Global Short Term Trend: Decline of 30-70%

Comments: Population size in the northwestern Hawaiian Islands is declining, while range and population size in the main Hawaiian Islands are increasing; overall the population is declining (NMFS 2007). Modeling predicts that the population will fall below 1,000 animals in the next five years (NMFS 2007). During the period 1998-2006, the nonpup population at the six major reproductive sites in the northwestern Hawaiian Islands declined by an average of 3.9 percent per year (NMFS 2007).

Global Long Term Trend: Decline of 50-70%

Comments: The species declined by about 50 percent between the late 1950s and the mid-1970s, and beach counts of nonpups (juveniles, sub-adults and adults) declined by 66 percent between 1958 and 2006 (NMFS 2007).

Degree of Threat: A : Very threatened throughout its range communities directly exploited or their composition and structure irreversibly threatened by man-made forces, including exotic species

Comments: Primary threats in the northwestern Hawaiian Islands are 1) food limitation that could be due to changes in oceanographic conditions, competition with fisheries, or competition with other predators; 2) entanglement in marine debris, and 3) predation by sharks, especially on pre-weaned and recently weaned pups. An emerging threat in this region may be the loss of terrestrial habitat due to sea level increases resulting from global warming (Baker et al. 2006). Primary threats on main Hawaiian Islands are 1) interactions with recreational fishing gear, 2) possible transmission of diseases from domestic pets and livestock to seals, and 3) disturbance of seals that haul out on beaches heavily used by people. [NMFS 2007]

Potential disease outbreaks could have a devastating effect due to the currently small population size and limited geographic range. Due to low juvenile survival and an aging, breeding female population, the breeding female population is declining and birth rates will continue to decline.

Restoration Potential: Main Hawaiian Islands could support a larger population of seals if appropriate management actions were in place (NMFS 2007).

Biological Research Needs: See management information.

Needs: See management information.

Present day Hawaiian monk seal populations represent a fraction of their historical abundances. Although recovery efforts are now underway, the total cost of these efforts over the next 50 years is estimated to be about 385 million dollars. Also, in compliance with the National Marine Fisheries Service recovery plan for Hawaiian monk seals, important feeding and reproductive sites, typically beaches, have been closed to public access. Finally, they occasionally remove fish from commercial trolling lines.

Currently, Hawaiian monk seals have little to no economic importance. However, during the mid-19th century, when Hawaii was first claimed by the United States, Hawaiian monk seals were killed for their skin, oil, and meat.

Comments: Relatively unwary, exploited historically, mainly by Europeans in ships.

Stewardship Overview: Four key actions are required to alter the trajectory of the Hawaiian monk seal population and to move the species towards recovery (NMFS 2007): 1. Improve the survivorship of females, particularly juveniles, in subpopulations in the northwestern Hawaiian Islands (NWHI). To do this requires the following: maintaining and enhancing existing protection and conservation of habitat and prey base; targeting research to better understand the factors that result in poor juvenile survival; intervening where appropriate to ensure higher survival of juvenile and adult females; continuing actions to protect females from individual and multiple male aggression and to prevent excessive shark predation; and continuing actions to remove marine debris and reduce mortality of seals due to entanglement. 2. Maintain the extensive field presence during the breeding season in the NWHI. Field presence is critical not just to the monitoring and research efforts, but also to carry out the active management and conservation of Hawaiian monk seal subpopulations in these areas. 3. Ensure the continued natural growth of the Hawaiian monk seal in the main Hawaiian Islands (MHI) by reducing threats including interactions with recreational fisheries, disturbance of mother-pup pairs, disturbance of hauled out seals, and exposure to human and domestic animal diseases. This should be accomplished with coordination of all federal, state, local and nongovernment parties, volunteer networks, and increased outreach and education in order to develop a culture of co-existence between humans and seals in the MHI. 4. Reduce the probability of the introduction of infectious diseases into the Hawaiian monk seal population.

NMFS (2007) listed the following 14 categories of actions as necessary for the recovery of the Hawaiian monk seal: 1 Investigate and mitigate factors affecting food limitation 2. Prevent entanglements of monk seals. 3. Reduce shark predation on monk seals. 4. Minimize the risk of exposure to or spread of infectious disease. 5. Conserve Hawaiian monk seal habitat. 6. Reduce Hawaiian monk seal interactions with fisheries. 7. Reduce male aggression toward pups/immature seals and adult females. 8. Reduce the likelihood and impact of human interactions. 9. Investigate and develop response to biotoxin impacts. 10. Reduce impacts from compromised and grounded vessels. 11. Reduce the impacts of contaminants. 12. Continue population monitoring and research. 13. Create and implement a main Hawaiian Islands Hawaiian Monk Seal. Management Plan. 14. Implement the Recovery Plan for the Hawaiian Monk Seal.