How did the dugong, which is indistinguishable from a manatee, become the prototype of a mermaid?

Recently, a study jointly completed by scientists from the Chinese Academy of Sciences and the Zoological Society of London and published in the British journal Royal Society Open Science stated that China's mermaid prototype "dugong" has experienced rapid population collapse in recent decades.

It is now "functionally extinct" in China.

Someone asked: Is the dugong a manatee? People often say on the Internet that dugongs are dugongs and manatees are manatees, and they are not the same kind of animals. In fact, this statement is biased. This article will introduce you to the dugong and its "relatives".

Dugongs belong to the order Sirenia, which is a type of aquatic mammal that is mainly herbivorous . There are two existing families in the order Sirenia: Trichechidae and Dugongidae.

There are three existing species of Manatee: Amazon manatee, American manatee, and African manatee.

There is one extant species in the Dugong family: the dugong.

Distribution map of the order Sirenia: Green is the American manatee, red is the Amazon manatee, orange is the African manatee, blue is the dugong, and the yellow circle is the Steller's sea cow (Hydrodamalis gigas), which also belongs to the dugong family and became extinct in the 18th century.

Image credit: B Kimmel

How to distinguish between Manatee and Dugong?

The most obvious difference between the Sirenia and Dugong families is their tails. The Sirenia family, which includes the Amazon manatee, the West African manatee, and the American manatee, has a round paddle-shaped tail, like the "round fan" used by ancient court ladies to cool off. The Dugong family's tail, on the other hand, is like the caudal fin of a whale, shaped like a "V".

There are obvious differences between the tails of the Manatee and the Dugong

Image source: Marine Science, Sun Yat-sen University

However, there is an exception. The Stellar sea cow belongs to the dugong family, and its tail is also in the shape of a "V". It can be called a "giant" in the sea, with a body length of up to 9 meters, far exceeding all manatees and dugongs today. However, the Stellar sea cow became extinct in the 18th century due to overfishing by humans.

German zoologist Georg Wilhelm Steller measuring the body data of a Steller's sea cow in 1742

Image credit: Stejneger

01

Dugong

The distribution range of dugongs is far wider than that of manatees. When dugongs were at their most prosperous, they could be seen almost everywhere along the 140,000 kilometers of coastline north and south of the equator, from the western Pacific to the Indian Ocean. Their distribution spans more than 30 countries around the world.

Pictured is a dugong foraging on the seabed of Marsa Alam, Egypt

Photo credit: Alberto Scarani

Dugongs like to eat tropical or subtropical seaweed in shallow waters. When eating, they are accustomed to pulling out the whole seaweed with the roots. If they cannot pull it out, dugongs will eat their leaves or stems.

Above: A dugong swims with fish near Ramen Island, Vanuatu. Photo credit: Simon Naunton

Below: A mother and child dugong swim together in the waters near East Timor. Photo credit: Nick Hobgood

Dugongs are shy by nature and do not like to approach humans.

Most dugongs can hold their breath underwater for 2.5 minutes, and some can even hold their breath for 6-8 minutes. They can dive to a depth of nearly 40 meters. Dugong cubs often interact with their mothers, such as touching each other with their bodies, and sometimes stretching out their tails to touch their mothers for comfort.

[Population status]

Currently, the world's dugongs are mainly distributed in the coastal areas of northern Australia. Their numbers have dropped sharply due to human hunting and habitat destruction.

According to aerial surveys in the 1990s, there were an estimated 100,000 dugongs worldwide, with 85,000 in Australia alone.

In 2000, the dugong was listed as a vulnerable (VU) species by the IUCN. Today, most countries and regions in the world have established legal protection for dugongs, and only some islands in northern Australia and indigenous people in western Papua New Guinea are allowed to hunt dugongs.

In my country, stranded dugongs were found in coastal waters of Guangdong, Guangxi, Hainan, etc. before the 1970s. With the development of economy, such as the development of marine aquaculture in the waters where dugongs are found, dugongs are threatened by accidental capture by fishing boats, illegal killing, and reduction of food sources (degradation of seagrass habitat), and their numbers have dropped sharply.

At the end of 1999, a dead dugong was found in the waters near Beihai, Guangxi, which was the last dead dugong found around the Hepu Dugong National Nature Reserve in my country. In 2008, a dugong was found in Dongfang City, Hainan Province, which was the last record of a dugong found in my country.

02

Amazon manatee ( Trichechus inunguis )

Amazon manatees are only distributed in the main rivers, lakes and other waters of the Amazon River basin in South America. They can be found in countries such as Brazil, Peru, Colombia and Ecuador.

The activities of Amazon manatees change with the seasons of the Amazon Basin. In the flood season, they appear in flooded forests or grasslands; in the dry season of July and August, the water level drops and some Amazon manatees are forced to stay in the depths of large lakes, where they usually stay until the end of the dry season in March of the following year.

Some scientists believe that they eat almost nothing during this period, relying entirely on stored fat in their bodies and a lower metabolic rate to sustain life. They can survive for seven or eight months without food or eating very little.

The Amazon manatee has brown or gray hair all over its body. Pictured is an Amazon manatee undergoing rehabilitation training at the Brazilian Institute of Environment and Renewable Natural Resources on Marajo Island, Brazil

Image source: KCO3

Photo credit: Anselmo-d'Affonseca

Amazon manatees have a white patch on their chest. They have no vestigial claws on their flippers, which is an important feature that distinguishes them from other manatees. Amazon manatees are also the smallest of the manatees, with an adult body length of about 1.62-2.3 meters.

The picture shows an Amazon manatee about to surface for air

Image credit: Dirk Meyer

Amazon manatees live almost entirely underwater, but they have to surface to breathe from time to time. The longest time a captive Amazon manatee has stayed underwater is 14 minutes.

[Population status]

The main threat to Amazon manatees is illegal hunting. The main reason why local indigenous people kill Amazon manatees is to use them for their livelihood.

The fat and skin of the Amazon manatee are used by locals to cook food and make medicine, and the meat is sold to farmers' markets to make money for a living.

More than 140,000 manatees were killed between 1935 and 1954. By 1977, the population was estimated at about 10,000.

Although many countries have enacted laws prohibiting the hunting of Amazon manatees, hunting incidents still occur. Between 2004 and 2015, illegal hunters in several regions of Brazil killed more than 650 Amazon manatees for their meat.

In 2008, the IUCN Red List listed the Amazon manatee as a vulnerable (VU) species.

Amazon manatee calves found in a tributary of Brazil's Capín River in 2015

Image source: Goianésia do Pará

03

American manatee (Trichechus manatus)

The American manatee, also known as the West Indian manatee, is found in shallow waters along the Atlantic coast and in some rivers in America.

The American manatee has sparse hair and gray skin. Its average body length is about 2.7-3.2 meters, making it the largest of the existing manatees. Based on the different waters where it lives, the American manatee can be divided into two subspecies:

1. Florida manatee (Trichechus manatus latirostris)

2. Antillean manatee (Trichechus manatus manatus)

Two American manatees, the Florida subspecies, basking in the sun in Haulover Canal at Merritt Island National Wildlife Refuge in Florida

Image credit: Gordon E. Robertson

1. Florida manatee (Trichechus manatus latirostris)

Florida manatees are mainly found along the coast of Florida, USA, west to Texas and north to Massachusetts.

Every summer, Florida manatees range as far as western Texas and northern Massachusetts, but in the winter they gather along the coast near Florida because only here the water is warm enough to help them survive the cold weather.

Florida Manatees in Crystal River, Florida

Photo credit: Cynthia Taylor

[Population status]

Florida manatees were listed as vulnerable (VU) by the IUCN in October 2007. They are mainly affected by physical damage from human ships (such as collisions), loss of warm water habitats, extremely high mortality during pregnancy, and red tides.

In 1997, scholars such as M. Marmontel and S. Humphrey predicted the survival capacity of the Florida manatee population. They believed that if the living environment of the Florida manatee continued to fail to improve and countries did not introduce effective protection regulations, the probability of extinction of the Florida manatee in the next 1,000 years would be as high as 44%.

A 2015-2016 aerial survey of Florida manatees indicated that there were approximately 8,800 Florida manatees in Florida (data revised in December 2018).

Manatee crossing sign at the South Florida Museum

Image credit: Bigmacthealmanac

2. Antillean manatee (Trichechus manatus manatus)

The Antillean manatee is sparsely distributed in the Caribbean region, and their "mysterious" figures can be seen sporadically in waters near Mexico in the north and Brazil in the south.

However, the most important habitat of the Antillean manatee is the coast of Belize, where the combination of rivers, lakes, lagoons and shallow seas has created a complex ecosystem of seagrass, mangroves and coral reefs, providing a variety of environments for their eating, drinking, defecating, urinating, giving birth and raising babies.

Normally, they mostly stay in the ocean or estuary environment between fresh and brackish water.

(a) A female Antillean manatee captured near Changuinola, Panama, in 1964;

(b) A female Antilles in Bocas del Toro, Panama, 1964;

(c) A male Antillean manatee weighing more than 360 kg in Bocas del Toro, Panama, 1964;

(d) Antillean manatee killed in a ship lock near Pedro Miguel Island in 1982

Image source: Hector M. Guzman et al.

[Population status]

The Antillean manatee, along with the Florida manatee, was listed as Vulnerable (VU) by the IUCN in October 2007.

The main threats to the Antillean manatee are the gradual fragmentation of its habitat and illegal hunting. In fact, due to the relatively turbid waters and poor light conditions in which the Antillean manatee inhabits, previous methods of surveying the Antillean manatee population (such as aviation and sonar) have not been very effective, so there is little population data on the Antillean manatee.

In 2016, Alves and other scholars studied the population of Antillean manatees in Brazil and believed that there were about 485-2221 of them in Brazil. In 2017, the U.S. Fish and Wildlife Service believed that there were more than 6,700 Antillean manatees.

An Antillean manatee was observed breathing in the Caralé River in the Andes.

Image source: Juan et al.

04

African manatee (Trichechus senegalensis)

The African manatee, also known as the West African manatee, is distributed in the waters along the west coast of Africa and extends inland into some inland rivers of West Africa (such as the Niger River).

Compared with the Amazon manatee that prefers fresh water and the American manatee that prefers the ocean, the West African manatee is more "easy-going". From salt water to the interface between salt water and fresh water and then to fresh water, such as oceans, estuaries, bays, lagoons, rivers, lakes, reservoirs and other waters can all become their paradise.

During the day, African manatees nap in shallow waters 1-2 meters deep.

In countries like Sierra Leone, during the flood season in June and July, African manatees migrate upstream along rivers until they encounter shallow water or waterfalls and cannot go any further, because flooding reduces their food sources.

Pictured is a West African manatee at the COEX Aquarium in Seoul, South Korea

Image credit: Mehdi Sadak 2ème compte

West African manatees are generally gray in color and covered with small transparent hairs.

However, because some algae and other small organisms often grow on the body of the African manatee, its body sometimes appears brown or green.

The picture shows an African manatee on land taken by researchers from the American Museum of Natural History in the last century.

African manatees can grow up to 4.5 meters in length. They usually move slowly, but when startled by a predator, they can move at speeds of about 30 kilometers per hour.

[Population status]

African manatees are threatened on many fronts.

First, illegal hunting: Poachers kill them for their meat, fat, bones, and skin in exchange for huge wealth. In Nigeria, Cameroon and other countries, African manatees are illegally sold to zoos and aquariums as pets. People in Mali, Chad and other countries also use the fat of African manatees to treat ear infections, rheumatism, skin diseases and other diseases.

African manatee caught in fishing net

Image source: inaturalist

Second, urban and agricultural development: The increase in dam construction has reduced the habitat of African manatees and caused physical damage to them. For example, African manatees often mistakenly enter turbines, water intake valves, and fishing nets and die accidentally.

The population of the African manatee has always been unclear. In 1998, Monica Silva of the University of the Azores conducted an eyewitness survey in three areas of Guinea-Bissau. The results of the study showed that only 256 African manatees were seen between 1990 and 1998. In the 2015 revision of the IUCN Red List of Threatened Species, the African manatee has been listed as a vulnerable (VU) species.

References

[1]Panama Canal Spillway. (1964d). Two new manatees join Chompers in lagoon here. Spillway, III(27).

[2]Montgomery, GG, Gale, NB, & Murdoch, WP (1982). Have manatee entered the eastern Pacific Ocean? Mammalia, 46, 257–258.

[3]Manatees". Canisius Ambassadors for Conservation. Archived from the original on 2010-06-29. Retrieved 2008-11-03.

[4] Husar, Sandra L. (1977). "Trichechus inunguis". Mammalian Species (72).

[5]Amaral, Rodrigo S. (27 October 2010). "Body weight/length relationship and mass estimation using morphometric measurements in Amazonian manatees Trichechus inunguis (Mammalia: Sirenia)". Marine Biodiversity Records. 3 (e105): 4.

[6]Reeves, Randall R.; Leatherwood, Stephen; Jefferson, Thomas A.; Curry, Barbara E.; Henningsen, Thomas. "Amazonian Manatees, Tricheus inunguis, In Peru: Distribution, Exploitation, and Conservation Status" (PDF). Retrieved 20 October 2014.

[7]Amazonian Manatee (Trichechus inunguis)". edgeofexistence.org. Zoological Society of London. Retrieved 22 October 2014.

[8]Marmontel, M.; de Souza, D.; Kendall, S. (2016). "Trichechus inunguis". IUCN Red List of Threatened Species. 2016.

[9]Halvorsen, KM; Keith, EO (2008). "Immunosuppression cascade in the Florida manatee (Trichechus manatus latirostris)".

[10]Runge, Michael C.; Sanders-Reed, Carol A.; Langtimm, Catherine A.; Hostetler, Jeffrey A.; Martin, Julien; Deutsch, Charles J.; Ward-Geiger, Leslie I.; Mahon, Gary L. (2017).

[11]"Manatee Mortality Statistics". Florida Fish And Wildlife Conservation Commission. Retrieved 2021-08-22.

[12] Galvez JA, Clarke CJ, Rosado, SK. (2013). "Ameliorating Threats to Manatees in the Heart of Belize".

[13]Marmontel, Miriam; Humphrey, Stephen R.; O'Shea, Thomas J. (1997). "Population Viability Analysis of the Florida Manatee (Trichechus manatus latirostris), 1976-1991". Conservation Biology. 11 (2): 467–481.

[14]Runge, Michael C.; Sanders-Reed, Carol A.; Langtimm, Catherine A.; Hostetler, Jeffrey A.; Martin, Julien; Deutsch, Charles J.; Ward-Geiger, Leslie I.; Mahon, Gary L. (2017). "Status and threats analysis for the Florida manatee (Trichechus manatus latirostris), 2016". Scientific Investigations Report.

[15]"Manatee Reclassified from Endangered to Threatened as Habitat Improves and Population Expands". fws.gov (Press release). Fish & Wildlife Service, US Department of the Interior. March 30, 2017.

[16]Alves, Maria Danise; Kinas, Paul Gerhard; Marmontel, Miriam; Borges, João Carlos Gomes; Costa, Alexandra Fernandes; Schiel, Nicola; Araújo, Maria Elisabeth (June 2016). "First abundance estimate of the Antillean manatee (Trichechus manatus manatus) in Brazil by aerial survey". Journal of the Marine Biological Association of the United Kingdom. 96(4):955–966.

[17]"Trichechus senegalensis". Encyclopedia of Life. Archived from the original on March 5, 2016.

[18]"West African manatee (Trichechus senegalensis)". Animal Corner. 2012.

[19]Jefferson, TA; Leatherwood, S.; Webber, MA "Trichechus senegalensis". nlbif. Archived from the original on 2014-03-02.

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The author of this article: Qu Shiyi, former editor of Discovery magazine, and master of cultural relics and museums.

This article is original from the Dou Wuxianpu website. Please indicate the source when reprinting.

Editor/Xiao Xitushuo