Hawaiian Monk Seal Facts

Scientific Name: Neomonachus schauinslandi

Hawaiian monk seal
Hawaiian monk seal. M Swiet Productions / Getty Images

Most seals live in icy waters, but the Hawaiian monk seal makes its home in the warm Pacific Ocean around Hawaii. The Hawaiian monk seal is one of only two current monk seal species. The other current species is the Mediterranean monk seal, while the Caribbean monk seal was declared extinct in 2008.

Native Hawaiians call the seal "ilio-holo-i-ka-uaua," which means "dog that runs in rough water." The monk seal's scientific name, Neomonachus schauinslandi, honors German scientist Hugo Schauinsland, who discovered a monk seal skull on Laysan Island in 1899.

Fast Facts: Hawaiian Monk Seal

  • Scientific Name: Neomonachus schauinslandi 
  • Common Names: Hawaiian monk seal, Ilio-holo-i-ka-uaua ("dog that runs in rough water")
  • Basic Animal Group: Mammal
  • Size: 7.0-7.5 feet
  • Weight: 375-450 pounds
  • Life Span: 25-30 years
  • Diet: Carnivorous
  • Habitat: Pacific Ocean around the Hawaiian Islands
  • Population: 1,400
  • Conservation Status: Endangered

Description

The monk seal gets its common name for the short hairs on its head, which are said to resemble those of a stereotypical monk. It is earless and lacks the ability to turn its hind flippers under its body. The Hawaiian monk seal is distinguishable from the harbor seal (Phoca vitulina) by its slender body, gray coat, and white belly. It also has black eyes and a short whiskered snout.

Habitat and Distribution

Hawaiian monk seals live in the Pacific Ocean around the Hawaiian Islands. Most of the breeding populations occur in the Northwest Hawaiian Islands, although monk seals are also found in the main Hawaiian Islands. The seals spend two-thirds of their time at sea. They haul-out to rest, molt, and give birth.

Diet and Behavior

The Hawaiian monk seal is a reef carnivore that preys on bony fish, spiny lobster, eels, octopus, squid, shrimp, and crabs. Juveniles hunt during the day, while adults hunt at night. Monk seals usually hunt in water ranging from 60-300 feet deep, but have been known to forage below 330 meters (1000 feet).

Monk seals are hunted by tiger sharks, Galapagos sharks, and great white sharks.

Reproduction and Offspring

Hawaiian monk seals mate in the water between June and August. In some breeding colonies, there is a much higher number of males than females, so "mobbing" of females occurs. Mobbing can lead to injuries or death, further skewing the sex ratio. Gestation takes about nine months.

The female monk seal gives birth on the beach to a single pup. While they are solitary animals, females have been known to care for pups born to other seals. Females stop eating during nursing and remain with the pups. At the end of six weeks, the mother leaves the pup and returns to the sea to hunt.

Females reach maturity around age 4. Researchers are not certain of the age at which males become mature. Hawaiian monk seals can live 25 to 30 years.

While nursing, a female seal stops eating and remains with her pup.
While nursing, a female seal stops eating and remains with her pup. Thessa Bugay / FOAP / Getty Images

Threats

Hawaiian monk seals face numerous threats. Natural threats include habitat reduction and degradation, climate change, skewed gender ratios, and low juvenile survival rates. Human hunting has resulted in extremely low genetic diversity within the species. Monk seals die from entanglement in debris and fishing gear. Introduced pathogens, including toxoplasmosis from domestic cats and leptospirosis from humans, have infected some seals. Even minimal human disturbance causes seals to avoid beaches. Overfishing has led to reduced prey abundance and increased competition from other apex predators.

Conservation Status

The Hawaiian monk seal is a conservation-reliant endangered species. This status indicates that human intervention is essential to the monk seal's survival, even if its population becomes self-sustaining. According to the IUCN Red List, only 632 mature individuals were identified on the species' last assessment in 2014. In 2016, there was an estimated total of 1,400 Hawaiian monk seals. Overall, the population is in decline, but the smaller population of seals living around the main Hawaiian islands is growing.

Disturbing a Hawaiian monk seal is illegal. Violators face a hefty fine.
Disturbing a Hawaiian monk seal is illegal. Violators face a hefty fine. Teresa Short / Getty Images

The Recovery Plan for the Hawaiian Monk Seal aims to save the species by increasing awareness of the seal's plight and intervening on its behalf. The plan includes increased monitoring of seal population, vaccination programs, dietary supplementation, protecting pups, and relocation of some animals to better habitats. In 2008, the monk seal was designated the state mammal of Hawaii.

Sources

  • Aguirre, A.; T. Keefe; J. Reif; L. Kashinsky; P. Yochem (2007). "Infectious disease monitoring of the endangered Hawaiian monk seal". Journal of Wildlife Diseases. 43 (2): 229–241. doi:10.7589/0090-3558-43.2.229
  • Gilmartin, W.G. (1983). "Recovery plan for the Hawaiian monk seal, Monachus schauinslandi". U.S. Department of Commerce, NOAA, National Marine Fisheries Service.
  • Kenyon, K.W.; Rice, D.W. (July 1959). "Life History Of the Hawaiian Monk Seal". Pacific Science. 13.
  • Perrin, William F.; Bernd Wursig; J. G. M. Thewissen (2008). Encyclopedia of Marine Mammals. Academic Press. p. 741. ISBN 978-0-12-373553-9. 
  • Schultz, J. K.; Baker J; Toonen R; Bowen B (2009). "Extremely Low Genetic Diversity in the Endangered Hawaiian Monk Seal (Monachus schauinslandi)". Journal of Heredity. 1. 100 (1): 25–33. doi:10.1093/jhered/esn077