Monachus schauinslandi


Taxonomy [top]

Kingdom Phylum Class Order Family

Scientific Name: Monachus schauinslandi
Species Authority: Matschie, 1905
Common Name/s:
English Hawaiian Monk Seal
Spanish Foca Fraile De Hawaii
Taxonomic Notes: The genus Monachus includes three geographically widely separated species: the Mediterranean Monk Seal, Monachus monachus; the Caribbean Monk Seal, Monachus tropicalis; and the Hawaiian Monk Seal, Monachus schauinslandi. Considered the most primitive of all living phocid species, monk seals have anatomical features that resemble those of seal fossils from 14-16 million years ago (Barnes et al. 1985). Studies of M. schauinslandi DNA microsatellites have found minor differences between animals from near the southeastern edge of the primary distribution at French Frigate Shoals and those at the far northwestern edge of the population at Kure Atoll (Kretzmann et al. 2001).

Assessment Information [top]

Red List Category & Criteria: Critically Endangered A3ce+4ce ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor/s: Lowry, L. & Aguilar, A. (IUCN SSC Pinniped Specialist Group)
Reviewer/s: Kovacs, K. & Lowry, L. (Pinniped Red List Authority)
Due to its relatively small population size, ongoing precipitous decline in numbers in spite of considerable conservation effort, and continuing threats from a variety of sources, the Hawaiian Monk Seal should be upgraded to Critically Endangered (CR).

IUCN Evaluation of the Hawaiian Monk Seal, Monachus schauinslandi
Prepared by the Pinniped Specialist Group

A. Population reduction Declines measured over the longer of 10 years or 3 generations
A1 CR > 90%; EN > 70%; VU > 50%
Al. Population reduction observed, estimated, inferred, or suspected in the past where the causes of the reduction are clearly reversible AND understood AND have ceased, based on and specifying any of the following:
(a) direct observation
(b) an index of abundance appropriate to the taxon
(c) a decline in area of occupancy (AOO), extent of occurrence (EOO) and/or habitat quality
(d) actual or potential levels of exploitation
(e) effects of introduced taxa, hybridization, pathogens, pollutants, competitors or parasites.

Most Hawaiian Monk Seals occur in the northwestern Hawaiian Islands (NWHI), and their population biology has been studied in detail there since 1983. In recent years, monk seals have been seen in increasing numbers in the main Hawaiian Islands (MHI), but the number of animals is relatively small and data about them are limited. In this evaluation, assessments of past abundance and projections of future abundance will therefore be based solely on the NWHI.

Based on the age distribution of the population and age-specific reproductive rates, the generation time for Hawaiian Monk Seals is 15 years. A comparison of the only available historical count (916 seals in 1958) to the most recent comparable count (293 seals in 2007) indicates a decline of 68% over 49 years. However, the causes for the reduction are not clearly reversible or understood, and have not ceased, so this criterion is not applicable.

A2, A3 & A4 CR > 80%; EN > 50%; VU > 30%
A2. Population reduction observed, estimated, inferred, or suspected in the past where the causes of reduction may not have ceased OR may not be understood OR may not be reversible, based on (a) to (e) under A1.

An estimate of the reduction in Hawaiian monk seal abundance in the past 49 years is 68% based on direct observation. While that interval is slightly more than three generations, the degree of reduction over the past 45 years has certainly been more than 50%. The causes of the reduction have not ceased, are not fully understood, and may not be reversible. This meets criterion A2(a) for Endangered.

A3. Population reduction projected or suspected to be met in the future (up to a maximum of 100 years) based on (b) to (e) under A1.

A detailed stochastic simulation model of the population projects that the population will decline 96% from its current (2007) abundance within the next 45 years (from 935 to 37). The likely causes of this decline will be changes in habitat quality, and effects of pathogens, competitors, or predators. This meets criterion A(3)(c and e) for Critically Endangered (CR).

A4. An observed, estimated, inferred, projected or suspected population reduction (up to a maximum of 100 years) where the time period must include both the past and the future, and where the causes of reduction may not have ceased OR may not be understood OR may not be reversible, based on (a) to (e) under A1.

Monk seal abundance in the NWHI declined 37% (from 1,488 to 935) from when detailed population monitoring began (1983) to the present (2007). A future population reduction is projected based on continuing low juvenile survival and the age/sex structure of the remaining population. Projecting from 2007 to 2028 (three generations from the initial count) predicts a likely reduction in population size to 201, 86% lower than the 1983 estimate. The likely causes of the future decline will be changes in habitat quality, and effects of pathogens, competitors, or predators. This meets criterion A(4)(c and e) for Critically Endangered (CR).

B. Geographic range in the form of either B1 (extent of occurrence) AND/OR B2 (area of occupancy)
B1. Extent of occurrence (EOO): CR < 100 km²; EN < 5,000 km²; VU < 20,000 km²

EOO for Hawaiian Monk Seals is > 20,000 km²

B2. Area of occupancy (AOO): CR < 10 km²; EN < 500 km²; VU < 2,000 km²

AOO for Hawaiian Monk Seals is > 2,000 km²

AND at least 2 of the following:
(a) Severely fragmented, OR number of locations: CR = 1; EN < 5; VU < 10
(b) Continuing decline in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) area, extent and/or quality of habitat; (iv) number of locations or subpopulations; (v) number of mature individuals.
(c) Extreme fluctuations in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) number of locations or subpopulations; (iv) number of mature individuals.

C. Small population size and decline
Number of mature individuals: CR < 250; EN < 2,500; VU < 10,000

The number of mature Hawaiian Monk Seal in the NWHI was 546 in 2007. The number of mature seals in the MHI has not been directly enumerated, but is estimated to be about 45 if the age structure in the MHI is similar to the NWHI. An estimate of the total number of mature individuals is then 591.

AND either C1 or C2:
C1. An estimated continuing decline of at least: CR = 25% in 3 years or 1 generation; EN = 20% in 5 years or 2 generations; VU = 10% in 10 years or 3 generations (up to a max. of 100 years in future)

The Hawaiian monk seal population in the NWHI has declined by 37% in the past 24 years (1983-2007; 1.6 generations). This meets criterion C1 for Endangered.

C2. A continuing decline AND (a) and/or (b):
(a i) Number of mature individuals in each subpopulation: CR < 50; EN < 250; VU < 1,000
(a ii) % individuals in one subpopulation: CR = 90?100%; EN = 95?100%; VU = 100%
(b) Extreme fluctuations in the number of mature individuals.

D. Very small or restricted population
Number of mature individuals: CR < 50; EN < 250; VU < 1,000 AND/OR restricted area of occupancy typically: AOO < 20 km² or number of locations < 5

The number of mature individuals in the Hawaiian Monk Seal population was approximately 591 in 2007. This meets the criterion for Vulnerable.

E. Quantitative analysis
Indicating the probability of extinction in the wild to be: CR > 50% in 10 years or 3 generations (100 years max.); EN > 20% in 20 years or 5 generations (100 years max.); VU > 10% in 100 years

A formal quantitative analysis of the probability of extinction of Hawaiian Monk Seals has not been conducted.

Listing recommendation ? The Hawaiian Monk Seal population is greatly reduced in size from historical levels, has been declining in abundance since at least 1958, and will without question continue to decline for some time into the future. The causes for the decline are only partially understood, have not ceased, and may not be reversible. The number of mature individuals within the population is currently only about 600. The total number of animals in the northwestern Hawaiian Islands, their core range, could drop to about 200 within the next 20 years. The Hawaiian Monk Seal qualifies for listing as Vulnerable under IUCN criterion D, for Endangered under criteria A2a and C1, and CR (Critically Endangered) under criteria A3ce and A4ce. Hawaiian Monk Seals should be listed as Critically Endangered (CR).
1996 Endangered (Baillie and Groombridge 1996)
1996 Endangered
1994 Endangered (Groombridge 1994)
1990 Endangered (IUCN 1990)
1988 Endangered (IUCN Conservation Monitoring Centre 1988)
1986 Endangered (IUCN Conservation Monitoring Centre 1986)
1982 Endangered (Thornback and Jenkins 1982)

Geographic Range [top]

Range Description: Hawaiian monk seals occur throughout the Hawaiian Island chain. Their six main reproductive sites are in the northwestern Hawaiian Islands at Kure Atoll, Midway Atoll, Pearl and Hermes Reef, Lisianski Island, Laysan Island, and French Frigate Shoals (National Marine Fisheries Service 2007). While sightings were previously rare in the main Hawaiian Islands, monk seals are now regularly seen there and births have been documented on all of the major islands (Baker and Johanos 2004). Sightings outside of the main range have occurred at Johnston Atoll, Palmyra Atoll, and Wake Island (Ragen and Lavigne 1999).

Hawaiian monk seals are non-migratory, and tend to remain near the atoll where they were born. However, some seals will relocate temporarily or permanently to other sites in the island chain, and long distance wanderers have been recorded.
United States (Hawaiian Is.)
FAO Marine Fishing Areas:
Pacific – eastern central; Pacific – northwest
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Monk seals in the northwestern Hawaiian Islands are well studied, with nearly all animals individually identifiable (through natural marks or flipper tags) and observed each year (Baker 2006). Less is known about the population biology of seals in the main Hawaiian Islands. The status of the Hawaiian monk seal through to 2006 was reviewed in detail in the recently revised Recovery Plan for the species (National Marine Fisheries Service 2007). For this IUCN review process, the Plan?s data were updated to include all information from 2007 and additional analyses were conducted by scientists from the National Marine Fisheries Service?s Pacific Islands Fisheries Science Center (Albert Harting, Thea Johanos-Kam, and Jason Baker, personal communication).

Female monk seals first give birth at five to ten years old. Births occur during all months of the year, with a peak in March-April. Age specific fecundity rates for mature animals are relatively low, 50-70%, and appear to differ among atolls (Harting et al. 2007). Males in this polygynous species patrol the water adjacent to rookeries, or haul-out near females with pups. Male dominated sex ratios have occurred at some colonies, and that has resulted in mobbing of estrus females that have been severely injured or killed in such events (NMFS 2007).

The generation time for Hawaiian monk seals, estimated as the average age of reproducing individuals, is 15 years. The best estimate of the total number of seals of all age classes in the northwestern Hawaiian Islands in 2007 is 935, with 546 of them being sexually mature. Adding to this a minimum estimate of 77 seals of all ages in the main Hawaiian Islands (not including Niihau) indicates a total population size of approximately 1,012, of which approximately 591 are sexually mature (assuming the age structure is similar in the northwestern and main Hawaiian Islands).

The earliest information on monk seal abundance comes from 1958 (Kenyon and Rice 1959, Rice 1960). These early data were not an estimate of total population size. They were counts of animals (not including pups) on beaches at a particular time, summed. Seals that were not hauled out at the time researchers visited the islands were not enumerated. Comparing the 1958 count (916 animals) to a beach count using similar methods in 2007 (293) suggests that the population has declined by 68% in 49 years.

Since 1983 the abundance of monk seals in the northwestern Hawaiian Islands has been estimated each year by having researchers spend enough time at each atoll to individually identify and count all, or nearly all, seals using that location. The total abundance estimate for 1983 was 1,488, which when compared to the total abundance estimate of 935 for 2007 indicates a decline of 37% in 24 years.

Since 1999 the population has been declining at a rate of 4.1% per year. Because detailed data are available on survival, reproduction, and age-structure of the population it is possible to use a stochastic simulation model (Harting 2002) to project likely abundances in the future. Using the model to project abundance three generations forward from the 1983 estimate (to 2028) predicts an overall reduction of 86% (from 1,488 to 201). Projecting abundance three generations forward from the most recent estimate (from 2007 to 2052) predicts a decline of 96% (from 935 to 37). These projections are derived using estimates of demographic rates from recent years and assume that those rates are representative of future conditions. Any changes in those rates (whether positive or negative) will of course alter the predicted trajectories.

Based on recorded births of pups, monk seal numbers in the main Hawaiian Islands appear to have increased in recent years (Baker and Johanos 2004). However, the number of animals in the main Islands is small, and the current status of the species depends primarily on the situation in the northwestern Hawaiian Islands.
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: Adult Hawaiian monk seals reach lengths of about 2.1 to 2.4 m and weigh 170-240 kg with females being somewhat longer and heavier than males. Pups are about 1 m and 16-18 kg at birth and when weaned 6 weeks later they weigh 50-100 kg (Kenyon 1981, Antonelis et al. 2003).

Monk seals are generally solitary, both on land and at sea. Even when seals gather together on land, they are not normally gregarious and only mothers and pups and recently weaned seals regularly make physical contact. On land, Hawaiian monk seals haul-out and breed on substrates of sand, coral or volcanic rock. Sandy beaches with shallow protected water near shore appear to be preferred for pupping (Westlake and Gilmartin 1990).

At-sea movements and habitat use of Hawaiian monk seals have been investigated using satellite-linked dive recorders and animal-born video cameras that have been put on seals in the northwestern Hawaiian Islands. Results show that they forage within atolls, in the shallow waters surrounding atolls and islands and farther offshore at submerged banks and reefs (Stewart et al. 2006). Seals carrying cameras searched for and preyed on benthic fish and invertebrates in areas of rubble and consolidated bottom material, along areas of transition of benthic habitat types, and also in deepwater coral beds (Parish et al. 2000, 2002).

Most dives that have been recorded have been less than 150 meters deep, although some individuals dove to more than 550 m (Stewart et al. 2006). Monk seals are known to eat a variety of fishes, eels, cephalopods and crustaceans (Goodman-Lowe 1998).

While the habitats of the Hawaiian monk seal are distributed over thousands of kilometers, the terrestrial habitat available for their use in the northwestern Hawaiian Islands is very limited. The total area of emergent land is only about 13.5 km² and only a fraction of that is suitable for use by seals (Ragen and Lavigne 1999).
Systems: Terrestrial; Marine

Threats [top]

Major Threat(s): Recovery of Hawaiian monk seals has been affected to an unknown degree by disturbance from military activities in the northwestern Hawaiian Islands including the alteration, development and occupation of bases on several key islands that started before World War II (Ragen and Lavigne 1999). However, the military has left the area and the vast majority of monk seals live where they are isolated from most direct human contact. The only permanent structures remaining in the northwestern Hawaiian Islands are U.S. Fish and Wildlife Service facilities at Tern Island and Midway Atoll and remnants of former Coast Guard facilities at Kure Atoll.

Current threats to monk seals are thoroughly reviewed and analyzed in NMFS (2007). The most crucial threats in the northwestern Hawaiian Islands at this time 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, largely fragments of net and line discarded by North Pacific fisheries; 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). The situation in the main Hawaiian Islands is somewhat different, with the main threats there being: 1) interactions with recreational fishing gear especially hookings and entanglements in gillnets; 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.

Conservation Actions [top]

Conservation Actions: The Hawaiian monk seal has been listed as endangered under the U.S. Endangered Species Act since 1976. That law contains a number of provisions to protect the seals and their critical habitat. They are also covered by a general prohibition against unpermitted taking by the U.S. Marine Mammal Protection Act of 1973. It is listed on CITES Appendix I.

Virtually all of the land and waters in the northwestern Hawaiian Islands is included in one or more protected areas (the Northwestern Hawaiian Islands State Marine Refuge, the Kure Atoll State Wildlife Refuge, the Hawaiian Islands National Wildlife Refuge, the Midway Atoll National Wildlife Refuge, the Northwestern Hawaiian Islands Coral Reef Ecosystem Reserve and the Papahanaumokuakea Marine National Monument) where human activities that could effect the seals or their habitats are either prohibited or strictly controlled.

Numerous efforts have been undertaken to identify sources of mortality for monk seals and to take management actions to mitigate factors that may be causing the continued population decline and preventing recovery (NMFS 2007). Important management efforts include: 1) cleaning up of marine debris and toxic chemicals; 2) minimizing human activities that could disturb seals hauled out on beaches; 3) removal of sharks suspected to be preying on seals; 4) translocation of adult males to adjust the sex ratio where mobbing was a problem; and 5) regulating fisheries to reduce the likelihood of direct and indirect interactions. In spite of these efforts the population has continued to decline. With the current low abundance, low survival rates, and declining trend there is a real chance that this species will go extinct in the foreseeable future. For that reason plans are being made to develop a facility where young seals can be cared for in captivity for a period of time in hopes that when they are released back to the wild they may have a better chance for survival.
Citation: Lowry, L. & Aguilar, A. (IUCN SSC Pinniped Specialist Group) 2008. Monachus schauinslandi. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <>. Downloaded on 17 April 2014.
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