Mammals

Monk seals are generally solitary both on land and at sea, with only mothers and pups and recently weaned seals regularly making physical contact. Female monk seals first give birth at 5-10 years old, giving birth to a single pup and remaining onshore for about 6 weeks. Births are most common from February to August, with most births occurring in March and April, but can take place at any time of year. The female will mate again about 3-4 weeks after weaning her pup, and 5-6 weeks later will haul out again for approximately two weeks to moult.

Hawaiian monk seals are opportunistic predators that forage near the sea floor, feeding on a range of fish, cephalopods and crustaceans. Adult seals spend approximately two-thirds of their time in the water, mainly foraging and travelling. Most dives that have been recorded have been less than 150 m deep, although some individuals can dive to more than 550 m. They are non-migratory, and tend to remain near the atoll where they were born. The average life expectancy is 20-25 years.

Hawaiian monk seals haul out on land to give birth, nurse their young, moult and rest. Shallow sandy beaches with a protective reef that provides shelter from sharks and large waves are the preferred pupping sites, but some females favour more isolated beaches where disturbance from other mother-pup pairs is less likely. Monk seals also use volcanic emergent reefs as haul-outs, and will use vegetation behind beaches to shelter from bad weather, rest at night, and avoid disturbance from other seals.

Movements and habitat use of monk seals at sea has been investigated using satellite-linked dive recorders and video cameras that have been attached to seals in the north-western Hawaiian Islands. Seals forage within and around atolls, further offshore along submerged banks and reefs, and also in transitional benthic habitats and deepwater coral beds.

Believed to number around 600 mature individuals.

Decreasing. The population is believed to have declined by 68% in 49 years.

Classified as Critically Endangered (CE A3ce+4ce) on the 2009 IUCN Red List of Threatened Species.

Hawaiian monk seals were nearly hunted to extinction in the late nineteenth century. Their subsequent recovery has been limited. In the north-western Hawaiian Islands, monk seals were threatened in the past by disturbance from military activities before and during World War II, and are now threatened by entanglement in discarded fishing gear and other marine debris, food limitation (possibly due to competition with fisheries), and predation by sharks. Loss of terrestrial habitat due to sea level increases resulting from global warming may also be an emerging threat in this region. The primary threats in the main Hawaiian Islands are interactions with recreational fishing gear (especially gill net entanglement and hookings), possible disease transmission from domestic pets and livestock, and disturbance at beaches that are heavily used by people.

The Hawaiian monk seal has been listed as endangered under the U.S. Endangered Species Act since 1976. This law contains a number of specific provisions for the protection of monk seals and their critical habitat. The status of the Hawaiian monk seal through to 2006 has been reviewed in detail in the recently revised Recovery Plan for the species.

Virtually all of the land and waters in the north-western Hawaiian Islands are now protected; in particular, the waters from 3-50 nautical miles around these islands were designated as the NWHI Coral Reef Ecosystem Reserve in 2000, with specific restrictions on human activities permitted within the Reserve. Monk seals in this region are well studied, and nearly all are individually identifiable (through natural marks or flipper tags). However, less is known about the population biology of seals in the main Hawaiian Islands.

Numerous efforts have also been undertaken to identify causes of mortality in Hawaiian monk seals, and to mitigate factors that may be preventing recovery and causing continued population declines. These actions have included regulating fisheries to reduce incidental by-catch and competition for fish, cleaning up marine debris and toxic chemicals, minimizing human disturbance on beaches, removing sharks suspected to be preying on seals, and translocating adult males to adjust sex ratios.

Despite active conservation efforts, Hawaiian monk seals still have low survival rates and continue to decline. In addition to maintaining all existing conservation initiatives for the species, public outreach and education activities involving all potential stakeholders should be strengthened. Plans are also being made to develop a facility where young monk seals can be cared for in captivity before re-release into the wild, in order to reduce high infant mortality.

National Oceanic and Atmospheric Administration     

Seal Conservation Society            

Marine Conservation Biology Institute

Baker, J. D., Polovina, J. J. & Howell, E. A. 2007. Effect of variable oceanic productivity on the survival of an upper trophic predator, the Hawaiian monk seal Monachus schauinslandi. Marine Ecology Progress Series 346: 277-283.

George, A. et al. 2007. Hawaiian monk seal (Monachus schauinslandi): status and conservation issues. National Oceanic and Atmospheric Administration Report.

Goodman-Lowe, G. D. 1998. Diet of the Hawaiian monk seal (Monachus schauinslandi) from the north-western Hawaiian Islands during 1991 to 1994. Marine Biology 132: 535-546.

Lowry, L. & Aguilar, A. 2008. Monachus schauinslandi. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.1. <www.iucnredlist.org>. Downloaded on 26 October 2009.

Schultz, J. K. et al. 2009. Extremely low genetic diversity in the endangered Hawaiian monk seal (Monachus schauinslandi). Journal of Heredity 100: 25-33.