Monk seal
Monk seals | |
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Hawaiian monk seal (top) and Mediterranean monk seal (bottom) | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Carnivora |
Clade: | Pinnipedia |
Family: | Phocidae |
Subfamily: | Monachinae |
Tribe: | Monachini Scheffer, 1958 |
Species | |
Monachus monachus | |
Hawaiian monk seal range | |
Mediterranean monk seal range |
Monk seals are earless seals of the tribe Monachini. They are the only earless seals found in tropical climates. The two genera of monk seals, Monachus and Neomonachus, comprise three species: the Mediterranean monk seal, Monachus monachus; the Hawaiian monk seal, Neomonachus schauinslandi; and the Caribbean monk seal, Neomonachus tropicalis, which became extinct in the 20th century. The two surviving species are now rare and in imminent danger of extinction. All three monk seal species were classified in genus Monachus until 2014, when the Caribbean and Hawaiian species were placed into a new genus, Neomonachus.
Monk seals have a slender body and are agile. They have a broad, flat snout with nostrils on the top. Monk seals are
All species experienced overhunting by
Etymology
The name "monk seal" (German Münchs-Robbe) was suggested by naturalist
Taxonomy and evolution
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Phylogenetic relations between monk seals and other earless seals [4] |
Monk seals are earless seals (true seals) of the tribe Monachini.[5] The tribe was first conceived by Victor Blanchard Scheffer in his 1958 book Seals, Sea Lions, and Walruses: A Review of the Pinnipedia.[6] The two genera of monk seals, Monachus and Neomonachus, comprise three species: the Mediterranean monk seal (Monachus monachus), the Hawaiian monk seal (Neomonachus schauinslandi), and the Caribbean monk seal (N. tropicalis), which became extinct in the 20th century. All three monk seal species were classified in genus Monachus until 2014, when comparison of the species' mitochondrial cytochrome b DNA sequences led biologists to place the Caribbean and Hawaiian species in a new genus, Neomonachus.[7][8]
Fossils of the Mediterranean and Caribbean species are known from the Pleistocene.[4] The time of divergence between the Hawaiian and Caribbean species, 3.7 million years ago (Mya), corresponds to the closing of the Central American Seaway by the formation of the Isthmus of Panama. The divergence between Mediterranean seals and the New World clade was dated to 6.3 Mya ago.[9]
Fossils of a Pliocene species of monk seal, Eomonachus belegaerensis, have been found in Taranaki region of New Zealand. This could possibly place the origins of the group in the Southern Hemisphere.[10][11] The only other fossil monk seal is Pliophoca etrusca, from the late Pliocene of Italy.[12]
Habitat
The Hawaiian monk seal, as the name suggests, lives solely in the
The habitat of the Mediterranean monk seal has changed over the years. Prior to the 20th century, they had been known to congregate, give birth, and seek refuge on open beaches. Since sealing had ended, they have left their former habitat and now only use sea caves for such behavior. More often than not, these caves are rather inaccessible to humans due to underwater entries, and because the caves are often along remote or rugged coastlines. Scientists have confirmed this is a recent adaptation, most likely due to the rapid increase in human population, tourism, and industry, which have caused increased disturbance by humans and the destruction of the species' natural habitat. Because of these seals' shy nature and sensitivity to human disturbance, they have slowly adapted to try to avoid contact with humans completely within the last century, and perhaps, even earlier. The coastal caves are, however, dangerous for newborns, and are causes of major mortality among pups when sea storms hit the caves.[15]
Caribbean monk seals were found in warm temperate, subtropical, and tropical waters of the Caribbean Sea, Gulf of Mexico, and the west Atlantic Ocean. They probably preferred to haul out at sites (low sandy beaches above high tide) on isolated and secluded atolls and islands, but occasionally visited the mainland coasts and deeper waters offshore. This species may have fed in shallow lagoons and reefs.[16]
Description
Monk seals are part of the family
The Mediterranean monk seal has a short, broad, and flat snout, with very pronounced, long nostrils that face upwards. The flippers are relatively short, with small, slender claws. The monk seal's physique is ideally suited for hunting its prey: fish, octopus, lobster, and squid in deep-water coral beds.[21] The fur coats of males is generally black, and brown or dark gray in females. Pups are about 3.3 feet (1 m) long and weigh around 33–40 pounds (15–18 kg), their skin being covered by 0.4-to-0.6-inch (1.0 to 1.5 cm) fur, usually dark brown or black. On their bellies, a white stripe occurs, which differs in color between the two sexes. This hair is replaced after 6–8 weeks by the usual short hair adults carry.[19]
The Hawaiian monk seal (whose Hawaiian name means "the dog that runs in rough waters")
Caribbean monk seals had a relatively large, long, robust body, and could grow to nearly 8 feet (2.4 m) in length and weighed 375 to 600 pounds (170 to 272 kg). Males were probably slightly larger than females, which is similar to Mediterranean monk seals. Like other monk seals, this species had a distinctive head and face. The head was rounded with an extended, broad muzzle. The face had relatively large, wide-spaced eyes, upward-opening nostrils, and fairly big whisker pads with long, light-colored, and smooth whiskers. When compared to the body, the animal's foreflippers were relatively short with little claws and the hindflippers were slender. Their coloration was brownish and/or grayish, with the underside lighter than the dorsal area. Adults were darker than the paler and more yellowish younger seals. Caribbean monk seals were also known to have algae growing on their pelages, giving them a slightly greenish appearance, which is similar to Hawaiian monk seals.[16]
Behavior
Diet and predation
Hawaiian monk seals mainly prey on reef-dwelling
Mediterranean monk seals are
Reproduction and development
Very little is known of the Mediterranean monk seal's reproduction. They are thought to be polygynous, with males being very territorial where they mate with females. Although no breeding season exists, since births take place year round, a peak occurs in October and November. This is also the time when caves are prone to wash out due to high surf or storm surge, which causes high mortality rates among pups, especially at the key Cabo Blanco colony. Pups make first contact with the water 2 weeks after their birth and are weaned around 18 weeks of age; females caring for pups go off to feed for an average of 9 hours.[19] Most individuals are believed to reach maturity at 4 years of age. The gestation period lasts close to a year. However, monk seals of the Cabo Blanco colony may have a gestation period lasting slightly longer than a year.[25]: 97 Mediterranean monk seals generally live to be 25 to 30 years old.[15]
Hawaiian monk seals are polygynous. The breeding season takes place throughout the year, excluding the fall, but peaks during April and May. Shark attacks cause a high pup mortality, from 19% to 39%. Pups are thought to be weaned around 6 weeks and reach sexual maturity at 3 years.[25]: 104–105 Their typical lifespan is 25 to 30 years.[22]
Not much is known of the Caribbean monk seal's reproduction. They likely bore a single pup every two years. Their gestation period, lactation period, and sexual maturity age are unknown.[25]: 102
Interactions with humans
Hawaii
Threats
In the 19th century, many seals were killed by
The Hawaiian monk seal has the lowest level of genetic variability among the 18 pinniped species, allegedly due to a population bottleneck caused by intense hunting in the 19th century. This limited genetic variability reduces the species's ability to adapt to environmental pressures and limits natural selection, thus increasing their risk of extinction. Given the monk seal's small population, the effects of disease could be disastrous.[29][30]
Entanglement can result in mortality, because when the seals get trapped in marine debris such as fishing nets, they cannot maneuver or reach the surface to breathe.[29] Marine fisheries can potentially interact with monk seals by direct and indirect relationships. Directly, the seal can become snared by fishing equipment, entangled in discarded debris, and even feed on fish refuse.[27] International law prohibits the intentional discarding of debris from ships at sea. Monk seals have one of the highest documented rates of entanglement of any pinniped species.[27]
Conservation
In 1909,
To raise awareness of the species' plight, on June 11, 2008, a state law designated the Hawaiian monk seal as Hawaii's official state mammal.[33]
Mediterranean
Threats
Several causes provoked a dramatic population decrease over time: on one hand, commercial hunting (especially during the Roman Empire and Middle Ages) and during the 20th century, eradication by fishermen, who used to consider it a pest due to the damage the seal causes to fishing nets when it preys on fish caught in them; and on the other hand, coastal urbanization and pollution. Currently, its entire population is estimated to be less than 600 individuals scattered throughout a wide distribution range, which qualifies this species as endangered. Its current very sparse population is one more serious threat to the species, as it only has two key sites that can be deemed viable. One is the Aegean Sea (250–300 animals in Greece, with the largest concentration of animals on Gyaros,[34] and some 100 in Turkey); the other important subpopulation is the Western Saharan portion of Cabo Blanco (around 200 individuals which may support the small, but growing, nucleus in the Desertas Islands – roughly 20 individuals[19]). Some individuals may be using coastal areas along other parts of Western Sahara, such as in Cintra Bay.[35] These two key sites are virtually in the extreme opposites of the species' distribution range, which makes natural population interchange between them impossible. All the other remaining subpopulations are composed of less than 50 mature individuals, many of them being only loose groups of extremely reduced size – often less than five individuals.[19] Consequently, low genetic variability exists.[36]
Cabo Blanco, in the Atlantic Ocean, is the largest surviving single population of the species, and the only remaining site that still seems to preserve a colony structure.
Conservation
In the
One of the largest groups among the foundations concentrating their efforts towards the preservation of the Mediterranean monk seal is the Mediterranean Seal Research Group (Akdeniz Foklarını Araştırma Grubu) operating under the Underwater Research Foundation (Sualtı Araştırmaları Derneği) in Turkey (also known as SAD-AFAG). The group has taken initiative in joint preservation efforts together with the Foça municipal officials, as well as phone, fax, and email hotlines for sightings.[39]
Caribbean
The extinction of the Caribbean monk seal was mainly triggered by overhunting in the eighteenth and nineteenth centuries to obtain the oil held within their blubber,[40] fueled by the large demand for seal products.[41] As early as 1688, sugar plantation owners sent out hunting parties to kill hundreds of seals every night for blubber oil to lubricate machinery.[42] The Caribbean monk seals' docile nature and lack of an instinctive fear of humans made it an easy target,[43] and hunting only ended (in the 1850s) because the population was too low for commercial use.[44] Overfishing of the reefs that sustained the Caribbean monk seal population also contributed to their extinction. Fish stock decline in the Caribbean starved the remaining populations.[45] Little was done to protect the Caribbean monk seal; by the time it was placed on the endangered species list in 1967, it was likely already extinct.[40]
References
- ^ Pacific Islands Fisheries Science Center (3 May 2022). "Hawaiian Monk Seal Population Surpasses 1,500!". NOAA Fisheries. Retrieved 20 December 2022.
- ^ Pacific Islands Fisheries Science Center (19 August 2022). "Monk Seal Pup Koalani to Be Relocated to Remote Beach Away from People After Weaning". NOAA Fisheries. Retrieved 20 December 2022.
- ^ The Curious Case of the Monk Seal — Why 'Monk'?
- ^ .
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- ^ Jemison, M. (15 May 2014). "Too valuable to lose: Extinct relative reveals rarity of last two remaining monk seal species". Smithsonian Science website. Smithsonian Institution. Archived from the original on 2014-05-15. Retrieved 15 May 2014.
- PMID 24899841.
- PMID 33171079.
- ^ Yarlagadda, Tara (13 November 2020). "Unusual Teeth Reveal A New Species And A Twist On Evolution". Inverse. Retrieved 14 November 2020.
- S2CID 84460049.
- ^ "Historical Timeline of the Hawaiian Monk Seal" (PDF). Pacific Islands Regional Office (NOAA). Honolulu, HI, USA: National Marine Fisheries Service, Pacific Islands Regional Office. June 29, 2011. Retrieved 19 November 2012.
- .
- ^ a b M. Johnson, William; A. Karamanlidis, Alexandros; Dendrinos, Panagiotis; Fernández de Larrinoa, Pablo; Gazo, Manel; Mariano González, Luis; Güçlüsoy, Harun; Pires, Rosa; Schnellmann, Matthias (2006). "Monk Seal Fact Files". The Monachus Guardian.
- ^ a b c "Caribbean Monk Seal (Monachus tropicalis)". NOAA – Office of Protected Resources. Retrieved 16 January 2016.
- ^ Gilmartin, William; Forcada, J. (2002). "Monk Seals". Encyclopedia of Marine Mammals, Eds: 756–759.
- ^ a b Encyclopedia of Marine Mammals, p. 741.
- ^ .
- ^ a b "Hawaiian Monk Seal (Neomonachus schauinslandi)". NOAA – Office of Protected Resources. Archived from the original on 13 January 2016. Retrieved 16 January 2016.
- ^ S2CID 84310964.
- ^ a b "Hawaiian Monk Seal". Marine Mammal Center. Retrieved 16 June 2016.
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- ^ ISBN 978-92-5-100512-5.
- ^ a b
ISBN 978-0-06-055804-8.
- ^ a b c d Antonelis, GA; et al. (2006). "Hawaiian monk seal (Monachus schauins-landi): status and conservation issues". Atoll Res Bull. 543: 75–101.
- ^ "Hawaiian Monk seal Monachus schauinslandi". National Geographic. 10 March 2011. Archived from the original on January 29, 2010. Retrieved 31 July 2016.
- ^ PMID 18815116.
- S2CID 73628238.
- ^ "Second Revision of Recovery Plan for the Hawaiian Monk Seal (Monachus schauinslandi)" (PDF). NOAA PIFSC Hawaiian Monk Seal Research. Honolulu, HI, USA: Pacific Islands Fisheries Science Center (NOAA). January 28, 2010 [2007]. Retrieved 16 January 2016.
- ^ Protected Resources Division." NOAA. N.p., n.d. Web. 21 Oct. 2013.
- ^ Gladden, Tracy. "Hawaiian monk seal is the new state mammal". KHNL NBC 8 Honolulu Hawaii. Archived from the original on 27 January 2013. Retrieved 23 May 2011.
- .
- ISBN 978-1-907263-31-6.
- PMID 15247308.
- ^ "MOm Website" (in Greek). mom.gr. Retrieved 11 June 2012.
- ^ "Important Moments for NMPANS" (in Greek). mom.gr. Archived from the original on 5 March 2016. Retrieved 16 January 2016.
- ^ "International Monk Seal Alliance". Sualtı Araştırmaları Derneği: Akdeniz Foku Araştırma Grubu. Retrieved 15 June 2016.
- ^ doi:10.1644/747.
- ^ Encyclopedia of Marine Mammals, pp. 585–588.
- ^ Gray, J (1850). Catalogue of the Specimens of Mammalia in the Collection of the British Museum. London. p. v.
{{cite book}}
: CS1 maint: location missing publisher (link) - S2CID 4065385.
- PMID 18348965.
Further reading
- Ronald M. Nowak (1999), Walker's Mammals of the World (6th ed.), Baltimore: Johns Hopkins University Press, LCCN 98023686
- Perrin, William F.; Bernd Wursig; J. G. M. Thewissen (2008). Encyclopedia of Marine Mammals. Academic Press. ISBN 978-0-12-373553-9.
External links