Hawaiian Monk Seal
(Monachus schauinslandi)
| Distribution and Numbers The second most endangered pinniped species in the world, there are an estimated 1,300 to 1,400 Hawaiian monk seals still in existence, mostly inhabiting the Northwestern Hawaiian Islands. The species' main reproductive populations are at French Frigate Shoals (the largest population), Laysan Island, Lisianski Island, Pearl and Hermes Reef, Midway Atoll and Kure Atoll. There are additional small colonies at Necker Island and Nihoa Island, while a small number of seals are also found in the main Hawaiian Islands. |
| Status The Hawaiian monk seal population was severely depleted by commercial sealers and other opportunistic hunters in the 19th century. Numbers recovered to some extent in the early 20th century but declined again after the middle of the century, most noticeably at the western end of the species' range. Beach counts, an index of monk seal population abundance, declined by approximately 40% between the late 1950s and the mid-1980s. From the late 1980s until the early 1990s Hawaiian monk seal numbers declined further due to a sharp reduction in the number of seals at the important French Frigate Shoals colony. This drop in numbers at the colony was caused primarily by extremely high juvenile mortality, the survival rates of monk seal pups from weaning to 1 year of age dropping from 80-90% to as low as 15%. |
 Photo: Mitch Craig, NMFS Honolulu Laboratory |
| Very few pups born at the colony survived to breeding age during the 1990s. Another possible factor in the reduction in numbers at French Frigate Shoals is the delay in the onset of reproduction which has been observed in female seals there compared to those at Laysan Island. The 1998 season saw an increase in the pup survival rate from weaning to 1 year of age at French Frigate Shoals to over 50% but the colony now consists almost entirely of older seals and it is expected that pup production there will decline significantly. The total number of Hawaiian monk seals has now been fairly stable since 1993 but a further reduction in numbers is likely. In January 1998 the Chief of Protected Species Investigations at the National Marine Fisheries Service (NMFS)'s Hawai'i branch stated that any further decline in Hawaiian monk seal numbers "could very seriously compromise" the survival of the species. |
| The lack of food resources caused by climatic variation and fisheries in the area has probably been a major cause of the recent decline and may be hampering the recovery of the species, particularly at French Frigate Shoals where evidence of limited prey availability has included small and emaciated pups as well as smaller nursing females than at other colonies. Of particular concern have been the effects of the commercial lobster fishery which has taken place in the Northwestern Hawaiian Islands since the early 1980s. Although the relative importance of different prey items in the diet of Hawaiian monk seals is not yet certain, preliminary results presented at a meeting in December 1999 revealed that lobsters may constitute a significant percentage of the diet of most juvenile and adult female monk seals at French Frigate Shoals. |
| In June 2000 the NMFS banned any further commercial lobster fishing in Hawaiian waters for the rest of the year. A coalition of environmental groups is also involved in an ongoing law suit seeking longer-term protection for the monk seal from the impacts of commercial fishing in the Northwestern Hawaiian Islands. As a result, the U.S. Federal District Court issued an injunction in November 2000 closing down the lobster fishery in order to protect the monk seals in the Northwestern Hawaiian Islands. The injunction was to remain in force until the NMFS could complete an Environmental Impact Statement as well as an analysis of the fishery's impacts under the Endangered Species Act. The Marine Mammal Commission has regularly requested that the NMFS prohibit the lobster fishery near French Frigate Shoals and other major monk seal colonies as a precautionary measure until sufficient studies can be carried out on the commercial lobster fishery's impact on monk seals, not only through the lobster catch but also through the fishery's bycatch of octopuses, crabs and small reef fish which are all components of the monk seal diet. |
| It is thought that one of the reasons for the general decline in monk seal numbers before the 1980s may have been disturbance caused by military and coastguard activities resulting in the abandonment of good quality pupping areas and of pups by their mothers. Hawaiian monk seals are generally very sensitive to disturbance and steps have now been taken to eliminate this problem. |
| The entanglement of Hawaiian monk seals in marine debris may also be a major cause of death, particularly of young seals which are far more prone to entanglement. During field visits to the majority of major monk seal breeding sites in 1999, 25 entangled seals were observed. A survey which took place at French Frigate Shoals during the winter of 1996-1997 estimated that the area contained more than 29,000 net fragments in waters less than 10m deep, mostly trawl webbing transported to the area from outside the Hawaiian islands by ocean currents. Scientists frequently remove dangerous marine debris from beaches and disentangle seals. Concerted efforts have also begun to remove debris from reefs within the seals' habitat, a cooperative federal-state-private cleanup operation in November 1998 amassing 7.5 tonnes of discarded fishing nets from 1.5 square kilometres of coral reef near major pupping beaches at French Frigate Shoals, while a similar cleanup at Lisianski Island and Pearl and Hermes Reef in 1999 amassed almost 23 tonnes of discarded fishing nets. |
 Photo: Mitch Craig, NMFS Honolulu Laboratory |
Other problems that may affect the ability of the species to recover include "mobbing" (see "Lifestyle" below). Since 1982 at least 66 seals have died or disappeared after being mobbed. Two adult males that had been particularly aggressive towards pups at French Frigate Shoals were captured and relocated in 1998. In recent years an increase in the occurrence of shark predation on monk seals has also been observed, mostly by Galapagos sharks. Pups that have not yet learned to avoid sharks are particularly vulnerable and it is thought that as many as 27% of the pups born at French Frigate Shoals in 1999 may have died due to shark predation. The lack of genetic diversity caused by the decline in population numbers may also compromise the future survival of the species, as may threats such as pollution. Biotoxin poisoning was implicated in a mass mortality of monk seals at Laysan Island in 1978. |
| The U.S. authorities have since 1984 undertaken several successful capture, rehabilitation and translocations of underweight monk seal pups from French Frigate Shoals to Kure Atoll in order to enhance the probability of the pups' survival and to rebuild colonies at the Atoll. However similar translocations to Midway Atoll in 1992-1993 resulted in most of the translocated pups disappearing or being found dead. After a change of procedures a total of 12 pups was captured in 1995 for transfer to Midway Atoll but these developed eye problems, resulting in the blindness of most of the pups and these seals are now being held in permanent captivity. Further translocations were postponed in 1998 when studies revealed the possible presence of antibodies to morbillivirus in seals tested at French Frigate Shoals. The virus has since been shown not to be present in the colony's monk seals but translocation is still suspended due to improved first-year survival rates for seals born there. A trial "headstart" programme was also undertaken at Kure Atoll in the 1980s where weaned pups were kept for a few months in an enclosure built at the atoll in order to increase their first-year survival prospects, reportedly with successful results. |
| The interactions of monk seals and active fisheries gear was highlighted in 1990 when a rapidly expanding pelagic swordfish longline fishery began operating near major monk seal breeding sites and several seals were found with longline hooks embedded in their mouths and skin. A protected species management zone was subsequently created around the Northwestern Hawaiian Islands banning pelagic longline fishing within 50 nautical miles of the islands. No seals have been found with embedded longline hooks since the creation of the zone. A demersal shark longline fishery that was recently opened in the islands has now closed down and the Western Pacific Regional Fishery Management Council is moving to ban demersal longlining permanently in the zone and in certain areas around the main Hawaiian Islands. This move is due to concerns regarding the impact of the fishery on both coastal sharks and on protected species such as monk seals. The Marine Mammal Commission has recommended that all future fisheries within the protected species management zone be subject to assessment of their likely impact on monk seals before they are allowed to take place. |
| There have been problems caused by fishing vessels running aground on reefs near monk seal habitat. In April 1999 a 29 metre longliner grounded off the coast of Kauai releasing 4,200 litres of diesel fuel, around 1,000 hooked monofilament fishing lines and various debris into the ocean. There were also worries that sharks might be attracted into the area by the boat's cargo of fish which had been released. In June 2000 a 26 metre longliner ran aground on a coral reef in the Northwestern Hawaiian Islands carrying over 20,000 litres of diesel fuel, kilometres of monofilament main line and thousands of branch lines containing hooks. Other potential problem areas that need to be monitored for effects on monk seals include recent interest in the harvest of coral in monk seal foraging habitat, entrapment hazards caused by the degrading sea wall at Tern Island (French Frigate Shoals), potentially toxic discards from fisheries, ecotourism activities at Midway Atoll, and recreational fisheries around the islands. |
| In January 2001 a new reserve was finalised, the Northwest Hawaiian Islands Coral Reef Ecosystem Reserve, covering 339,260 square kilometres (34 million hectares) along a 1,930km chain of Hawaiian islands. Under the terms of the reserve, oil, gas and mineral production and exploration is banned, commercial and recreational fishing is capped at pre-reserve levels, the removal of coral is banned, and dumping is prohibited. In addition, stricter regulations apply in 15 special areas within the reserve. |
| The Hawaiian monk seal is listed as Endangered under the U.S.
Endangered Species Act and as Depleted under the U.S. Marine Mammal Protection Act. The species is also listed as Endangered on the IUCN Red
List and as an Appendix I species under CITES. The seals' breeding areas in the Northwest Hawaiian Islands
are covered by either the Hawaiian Islands National Wildlife Refuge, the Midway Atoll
National Wildlife Refuge or the State of Hawai'i Seabird Sanctuary at Kure Atoll. Access
to all of these protected areas requires permits. The conservation, assessment and
recovery of the Hawaiian monk seal is the responsibility of the U.S. National Marine
Fisheries Service (NMFS)'s Honolulu Laboratory. |
 Photo: Mitch Craig, NMFS Honolulu Laboratory |
| Lifestyle Females appear to prefer relatively short lengths of beach, with very shallow water next to the shoreline, for pupping and nursing their pups. This is possibly to protect against rough waves and shark predation. They haul out several days before giving birth, pups mostly being born from February to July. Newborn pups have a black coat which they moult by the time that they have weaned and which will eventually be replaced by the adult coat of grey-brown on top, a lighter cream colour underneath. Mothers nurse their pups for 5-6 weeks after birth, remaining near to the birth site. They do not feed during this period and lose up to an estimated 90kg in weight. Females have been known to adopt an additional pup, sometimes after their own pup has died, and nursing pups are sometimes exchanged between mothers. After the mother leaves, the pup fasts for a few weeks, living off its reserves. The pup then gradually learns to feed and begins making longer trips away from its birth location. |
| The mating of Hawaiian monk seals usually occurs at sea and is rarely
seen. Some adult male Hawaiian monk seals exhibit an aggressive behaviour called
"mobbing" where they gang together and attempt to mate with, and by doing so
injure and often kill, adult females and immature seals of both sexes. This behaviour
seems to occur to a far greater extent in those populations where there are more males
than females. Not a great deal is known about the lifestyle of the Hawaiian monk seal
outside the breeding season, but they are known to be fairly solitary. Their prey is known
to include octopus, lobster and fish, including eels and flatfish, and they often feed
along the slopes of coral reefs at depths of up to 75-90m. Hawaiian monk seals do not
migrate, but there is a limited exchange of individuals between colonies. Sharks are their
main predators. |
| Statistics Adult Hawaiian monk seals weigh 180-270kg and the females are thought to be slightly larger than the males. Pups are born weighing about 11-15kg and measuring about 1m in length. Hawaiian monk seals have been known to dive to depths of 500m or more. Females give birth for the first time at 5-10 years of age. The maximum age for the species is 25-30 years, but few seals live that long. |
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