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Manatees (
family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
Trichechidae,
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
''Trichechus'') are large, fully aquatic, mostly herbivorous
marine mammal Marine mammals are aquatic mammals that rely on the ocean and other marine ecosystems for their existence. They include animals such as seals, whales, manatees, sea otters and polar bears. They are an informal group, unified only by their ...
s sometimes known as sea cows. There are three accepted living species of Trichechidae, representing three of the four living species in the order Sirenia: the
Amazonian manatee The Amazonian manatee (''Trichechus inunguis'') is a species of manatee that lives in the Amazon Basin in Brazil, Peru, Colombia and Ecuador. It has thin, wrinkled brownish or gray colored skin, with fine hairs scattered over its body and a wh ...
(''Trichechus inunguis''), the West Indian manatee (''Trichechus manatus''), and the
West African manatee The African manatee (''Trichechus senegalensis''), also known as the West African manatee, is a species of manatee that inhabits much of the western region of Africa – from Senegal to Angola. It is the only manatee species to be found in the ...
(''Trichechus senegalensis''). They measure up to long, weigh as much as , and have paddle-like tails. Manatees are herbivores and eat over 60 different freshwater and saltwater plants. Manatees inhabit the shallow,
marsh A marsh is a wetland that is dominated by herbaceous rather than woody plant species.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p Marshes can often be found ...
y coastal areas and rivers of the
Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexic ...
, the
Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United ...
, the
Amazon basin The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries of Boli ...
, and
West Africa West Africa or Western Africa is the westernmost region of Africa. The United Nations defines Western Africa as the 16 countries of Benin, Burkina Faso, Cape Verde, The Gambia, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Liberia, Mali ...
. The main causes of death for manatees are human-related issues, such as
habitat destruction Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...
and human objects. Their slow-moving, curious nature has led to violent collisions with propeller-driven boats and ships. Some manatees have been found with over 50 scars on them from propeller blades. Natural causes of death include adverse temperatures, predation by crocodiles on young, and disease.


Etymology

The etymology of the name is unclear, with connections having been made to
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
"hand" and to
pre-Columbian In the history of the Americas, the pre-Columbian era spans from the original settlement of North and South America in the Upper Paleolithic period through European colonization, which began with Christopher Columbus's voyage of 1492. Usually, ...
Taíno The Taíno were a historic Indigenous peoples of the Caribbean, indigenous people of the Caribbean whose culture has been continued today by Taíno descendant communities and Taíno revivalist communities. At the time of European contact in the ...
''manati'' "breast". The term ''sea cow'' is a reference to the species' slow, peaceful, herbivorous nature, reminiscent of that of
bovine Bovines (subfamily Bovinae) comprise a diverse group of 10 genera of medium to large-sized ungulates, including cattle, bison, African buffalo, water buffalos, and the four-horned and spiral-horned antelopes. The evolutionary relationship betwe ...
s.


Taxonomy

Manatees are three of the four living species in the order Sirenia. The fourth is the
Eastern Hemisphere The Eastern Hemisphere is the half of the planet Earth which is east of the prime meridian (which crosses Greenwich, London, United Kingdom) and west of the antimeridian (which crosses the Pacific Ocean and relatively little land from pole ...
's dugong. The Sirenia are thought to have evolved from four-legged land mammals more than 60 million years ago, with the closest living relatives being the
Proboscidea The Proboscidea (; , ) are a taxonomic order of afrotherian mammals containing one living family ( Elephantidae) and several extinct families. First described by J. Illiger in 1811, it encompasses the elephants and their close relatives. Fr ...
(
elephant Elephants are the largest existing land animals. Three living species are currently recognised: the African bush elephant, the African forest elephant, and the Asian elephant. They are the only surviving members of the family Elephantida ...
s) and Hyracoidea (
hyrax Hyraxes (), also called dassies, are small, thickset, herbivorous mammals in the order Hyracoidea. Hyraxes are well-furred, rotund animals with short tails. Typically, they measure between long and weigh between . They are superficially simila ...
es).


Description

Manatees weigh , and average in length, sometimes growing to and and females tend to be larger and heavier than males. At birth, baby manatees weigh about each. The female manatee has two teats, one under each flipper, a characteristic that was used to make early links between the manatee and elephants. The lids of manatees' small, widely spaced eyes close in a circular manner. The manatee has a large, flexible,
prehensile Prehensility is the quality of an appendage or organ that has adapted for grasping or holding. The word is derived from the Latin term ''prehendere'', meaning "to grasp". The ability to grasp is likely derived from a number of different orig ...
upper lip, used to gather food and eat and for social interaction and communication. Manatees have shorter snouts than their fellow sirenians, the dugongs. Manatee adults have no incisor or
canine Canine may refer to: Zoology and anatomy * a dog-like Canid animal in the subfamily Caninae ** ''Canis'', a genus including dogs, wolves, coyotes, and jackals ** Dog, the domestic dog * Canine tooth, in mammalian oral anatomy People with the surn ...
teeth, just a set of cheek teeth, which are not clearly differentiated into molars and
premolar The premolars, also called premolar teeth, or bicuspids, are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth ...
s. These teeth are repeatedly replaced throughout life, with new teeth growing at the rear as older teeth fall out from farther forward in the mouth, somewhat as
elephant Elephants are the largest existing land animals. Three living species are currently recognised: the African bush elephant, the African forest elephant, and the Asian elephant. They are the only surviving members of the family Elephantida ...
s' teeth do. At any time, a manatee typically has no more than six teeth in each jaw of its mouth. The manatee's tail is paddle-shaped, and is the clearest visible difference between manatees and dugongs; a dugong tail is fluked, similar in shape to that of a whale. The manatee is unusual among
mammals Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur o ...
in having just six
cervical vertebrae In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In ...
, a number that may be due to mutations in the
homeotic genes In evolutionary developmental biology, homeotic genes are genes which regulate the development of anatomical structures in various organisms such as echinoderms, insects, mammals, and plants. Homeotic genes often encode transcription factor protein ...
. All other mammals have seven cervical vertebrae, other than the two-toed and three-toed sloths. Like the
horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million yea ...
, the manatee has a simple stomach, but a large
cecum The cecum or caecum is a pouch within the peritoneum that is considered to be the beginning of the large intestine. It is typically located on the right side of the body (the same side of the body as the appendix, to which it is joined). The wo ...
, in which it can digest tough plant matter. Generally, the intestines are about 45 meters, unusually long for an animal of the manatee's size.


Evolution

Fossil remains of manatee ancestors - also known as sirenians - date back to the
Early Eocene In the geologic timescale the Ypresian is the oldest age or lowest stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by the Eocene Lutetian Age. The Ypresian ...
. It is thought that they reached the isolated area of the South American continent and became known as Trichechidae. In the
Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene Epoch made up of two stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million years ago) to 5.333 Ma. The ...
, trichechids were likely restricted in South American coastal rivers and they fed on many freshwater plants.
Dugongs The dugong (; ''Dugong dugon'') is a marine mammal. It is one of four living species of the order Sirenia, which also includes three species of manatees. It is the only living representative of the once-diverse family Dugongidae; its closest ...
inhabited the West Atlantic and Caribbean waters and fed on seagrass meadows instead. As the sea grasses began to grow, manatees adapted to the changing environment by growing supernumerary molars. Sea levels lowered and increased erosion and silt runoff was caused by
glaciation A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate bet ...
. This increased the tooth wear of the bottom-feeding manatees.


Behavior

Apart from mothers with their young, or males following a receptive female, manatees are generally solitary animals. Manatees spend approximately 50% of the day sleeping submerged, surfacing for air regularly at intervals of less than 20 minutes. The remainder of the time is mostly spent grazing in shallow waters at depths of . The
Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and ...
subspecies (''T. m. latirostris'') has been known to live up to 60 years.


Locomotion

Generally, manatees swim at about . However, they have been known to swim at up to in short bursts.


Intelligence and learning

Manatees are capable of understanding discrimination tasks and show signs of complex associative learning. They also have good
long-term memory Long-term memory (LTM) is the stage of the Atkinson–Shiffrin memory model in which informative knowledge is held indefinitely. It is defined in contrast to short-term and working memory, which persist for only about 18 to 30 seconds. Long-t ...
. They demonstrate discrimination and task-learning abilities similar to
dolphin A dolphin is an aquatic mammal within the infraorder Cetacea. Dolphin species belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the b ...
s and
pinniped Pinnipeds (pronounced ), commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals. They comprise the extant families Odobenidae (whose only living member is the ...
s in acoustic and visual studies.(Marine Mammal Medicine, 2001, Leslie Dierauf & Frances Gulland, CRC Press) Social interactions between manatees are highly complex and intricate, which may indicate higher intelligence than previously thought, although they remain poorly understood by science.


Reproduction

Manatees typically breed once every two years; generally only a single calf is born.
Gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pr ...
lasts about 12 months and to wean the calf takes a further 12 to 18 months, although females may have more than one
estrous cycle The estrous cycle (, originally ) is the set of recurring physiological changes that are induced by reproductive hormones in most mammalian therian females. Estrous cycles start after sexual maturity in females and are interrupted by anestro ...
per year.


Communication

Manatees emit a wide range of sounds used in communication, especially between cows and their calves. Their ears are large internally but the external openings are small, and they are located four inches behind each eye. Adults communicate to maintain contact and during sexual and play behaviors. Taste and smell, in addition to sight, sound, and touch, may also be forms of communication.


Diet

Manatees are herbivores and eat over 60 different freshwater (e.g., floating hyacinth, pickerel weed, alligator weed, water lettuce, hydrilla, water celery, musk grass,
mangrove A mangrove is a shrub or tree that grows in coastal saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evolution in severa ...
leaves) and saltwater plants (e.g., sea grasses, shoal grass, manatee grass, turtle grass, widgeon grass, sea clover, and marine algae). Using their divided upper lip, an adult manatee will commonly eat up to 10%–15% of their body weight (about 50 kg) per day. Consuming such an amount requires the manatee to graze for up to seven hours a day. To be able to cope with the high levels of cellulose in their plant based diet, manatees utilize hindgut fermentation to help with the digestion process. Manatees have been known to eat small numbers of fish from nets.


Feeding behavior

Manatees use their flippers to "walk" along the bottom whilst they dig for plants and roots in the substrate. When plants are detected, the flippers are used to scoop the vegetation toward the manatee's lips. The manatee has prehensile lips; the upper lip pad is split into left and right sides which can move independently. The lips use seven muscles to manipulate and tear at plants. Manatees use their lips and front flippers to move the plants into the mouth. The manatee does not have front teeth, however, behind the lips, on the roof of the mouth, there are dense, ridged pads. These horny ridges, and the manatee's lower jaw, tear through ingested plant material.


Dentition

Manatees have four rows of teeth. There are 6 to 8 high-crowned, open-rooted molars located along each side of the upper and lower jaw giving a total of 24 to 32 flat, rough-textured teeth. Eating gritty vegetation abrades the teeth, particularly the enamel crown; however, research indicates that the enamel structure in manatee molars is weak. To compensate for this, manatee teeth are continually replaced. When anterior molars wear down, they are shed. Posterior molars erupt at the back of the row and slowly move forward to replace these like enamel crowns on a conveyor belt, similarly to
elephant Elephants are the largest existing land animals. Three living species are currently recognised: the African bush elephant, the African forest elephant, and the Asian elephant. They are the only surviving members of the family Elephantida ...
s. This process continues throughout the manatee's lifetime. The rate at which the teeth migrate forward depends on how quickly the anterior teeth abrade. Some studies indicate that the rate is about 1 cm/month although other studies indicate 0.1 cm/month.


Ecology


Range and habitat

Manatees inhabit the shallow,
marsh A marsh is a wetland that is dominated by herbaceous rather than woody plant species.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p Marshes can often be found ...
y coastal areas and rivers of the
Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexic ...
and the
Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United ...
(''T. manatus'', West Indian manatee), the
Amazon basin The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries of Boli ...
(''T. inunguis'',
Amazonian manatee The Amazonian manatee (''Trichechus inunguis'') is a species of manatee that lives in the Amazon Basin in Brazil, Peru, Colombia and Ecuador. It has thin, wrinkled brownish or gray colored skin, with fine hairs scattered over its body and a wh ...
), and
West Africa West Africa or Western Africa is the westernmost region of Africa. The United Nations defines Western Africa as the 16 countries of Benin, Burkina Faso, Cape Verde, The Gambia, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Liberia, Mali ...
(''T. senegalensis'',
West African manatee The African manatee (''Trichechus senegalensis''), also known as the West African manatee, is a species of manatee that inhabits much of the western region of Africa – from Senegal to Angola. It is the only manatee species to be found in the ...
). West Indian manatees prefer warmer temperatures and are known to congregate in shallow waters. They frequently migrate through
brackish water Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...
estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environme ...
to
freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does incl ...
springs. They cannot survive below 15 °C (60 °F). Their natural source for warmth during winter is warm, spring-fed rivers.


West Indian

The coast of the state of
Georgia Georgia most commonly refers to: * Georgia (country), a country in the Caucasus region of Eurasia * Georgia (U.S. state), a state in the Southeast United States Georgia may also refer to: Places Historical states and entities * Related to the ...
is usually the northernmost range of the West Indian manatees because their low
metabolic rate Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...
does not protect them in cold water. Prolonged exposure to water below 20 °C (68 °F) can cause "cold stress syndrome" and death. Florida manatees can move freely between fresh water and salt water. Manatees have been seen as far north as
Cape Cod Cape Cod is a peninsula extending into the Atlantic Ocean from the southeastern corner of mainland Massachusetts, in the northeastern United States. Its historic, maritime character and ample beaches attract heavy tourism during the summer mont ...
, and in 1995 and again in 2006, one was seen in New York City and
Rhode Island Rhode Island (, like ''road'') is a U.S. state, state in the New England region of the Northeastern United States. It is the List of U.S. states by area, smallest U.S. state by area and the List of states and territories of the United States ...
's
Narragansett Bay Narragansett Bay is a bay and estuary on the north side of Rhode Island Sound covering , of which is in Rhode Island. The bay forms New England's largest estuary, which functions as an expansive natural harbor and includes a small archipelago. Sm ...
. A manatee was spotted in the Wolf River harbor near the
Mississippi River The Mississippi River is the List of longest rivers of the United States (by main stem), second-longest river and chief river of the second-largest Drainage system (geomorphology), drainage system in North America, second only to the Hudson B ...
in downtown Memphis in 2006, and was later found dead downriver in McKellar Lake. Another manatee was found dead on a New Jersey beach in February 2020, considered especially unusual given the time of year. At the time of the manatee's discovery, the water temperature in the area was below 6.5 °C (43.7 °F). The West Indian manatee migrates into Florida rivers—such as the
Crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...
, the
Homosassa Homosassa is a census-designated place (CDP) in Citrus County, Florida, United States. The population was 2,578 at the 2010 census. History Homosassa is derived from a Seminole Indian name meaning either "river of fishes" or "pepper ridge". In ...
, and the Chassahowitzka rivers, whose headsprings are 22 °C (72 °F) all year. Between November and March each year, about 600 West Indian manatees gather in the rivers in
Citrus County, Florida Citrus County is a county located on the west central coast of the U.S. state of Florida. As of the 2020 census, the population was 153,843. Its county seat is Inverness, and its largest community is Homosassa Springs. Citrus County compri ...
such as the
Crystal River National Wildlife Refuge The Crystal River National Wildlife Refuge is part of the United States National Wildlife Refuge (NWR) System, located in Kings Bay, in the town of Crystal River, and consists of 20 islands and several small parcels of land. The refuge (only a ...
. In winter, manatees often gather near the warm-water outflows of power plants along the Florida coast, instead of migrating south as they once did. Some conservationists are concerned that these manatees have become too reliant on these artificially warmed areas. The U.S. Fish and Wildlife Service is trying to find a new way to heat the water for manatees that depended on plants that have closed. Studies suggest that Florida manatees need access to fresh water for proper regulation of water and salts in their bodies. Accurate population estimates of the Florida manatee (''T. manatus'') are difficult. They have been called scientifically weak because they vary widely from year to year, some areas showing increases, others decreases, and little strong evidence of increases except in two areas. Manatee counts are highly variable without an accurate way to estimate numbers: In Florida in 1996, a winter survey found 2,639 manatees; in 1997, a January survey found 2,229, and a February survey found 1,706. A statewide synoptic survey in January 2010 found 5,067 manatees living in Florida, the highest number recorded to that time. As of January 2016, the USFWS estimates the range-wide manatee population to be at least 13,000; as of January 2018, at least 6,100 are estimated to be in Florida.
Population viability Population viability analysis (PVA) is a species-specific method of risk assessment frequently used in conservation biology. It is traditionally defined as the process that determines the probability that a population will go extinct within a give ...
studies conducted in 1997 found that decreasing adult survival and eventual extinction were a probable future outcome for Florida manatees unless they got more protection. The U.S. Fish and Wildlife Service proposed downgrading the manatee's status from endangered to threatened in January 2016 after more than 40 years of the manatee's being classified as on the endangered.


Amazonian

The freshwater Amazonian manatee (''T. inunguis'') inhabits the Central Amazon Basin in
Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
, eastern
Perú , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = Seal (emblem), National seal , national_motto = "Fi ...
, southeastern
Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the ...
, but not
Ecuador Ecuador ( ; ; Quechua: ''Ikwayur''; Shuar: ''Ecuador'' or ''Ekuatur''), officially the Republic of Ecuador ( es, República del Ecuador, which literally translates as "Republic of the Equator"; Quechua: ''Ikwadur Ripuwlika''; Shuar: ' ...
. It is the only exclusively freshwater manatee, and is also the smallest. Since they are unable to reduce peripheral heat loss, it is found primarily in tropical waters.


West African

They are found in coastal marine and estuarine habitats, and in freshwater river systems along the west coast of Africa from the
Senegal River ,french: Fleuve Sénégal) , name_etymology = , image = Senegal River Saint Louis.jpg , image_size = , image_caption = Fishermen on the bank of the Senegal River estuary at the outskirts of Saint-Louis, Senega ...
south to the
Cuanza River The Kwanza River, also known as the Coanza, the Quanza, and the Cuanza, is one of the longest rivers in Angola. It empties into the Atlantic Ocean just south of the national capital Luanda. Geography The river is navigable for about from its ...
in
Angola , national_anthem = "Angola Avante"() , image_map = , map_caption = , capital = Luanda , religion = , religion_year = 2020 , religion_ref = , coordinat ...
. They live as far upriver on the
Niger River The Niger River ( ; ) is the main river of West Africa, extending about . Its drainage basin is in area. Its source is in the Guinea Highlands in south-eastern Guinea near the Sierra Leone border. It runs in a crescent shape through Mal ...
as Koulikoro in
Mali Mali (; ), officially the Republic of Mali,, , ff, 𞤈𞤫𞤲𞥆𞤣𞤢𞥄𞤲𞤣𞤭 𞤃𞤢𞥄𞤤𞤭, Renndaandi Maali, italics=no, ar, جمهورية مالي, Jumhūriyyāt Mālī is a landlocked country in West Africa. Ma ...
, from the coast.


Predation

In relation to the threat posed by humans, predation does not present a significant threat to manatees. When threatened, the manatee's response is to dive as deeply as it can, suggesting that threats have most frequently come from land dwellers such as humans rather than from other water-dwelling creatures such as caimans or sharks.


Relation to humans


Threats

The main causes of death for manatees are human-related issues, such as habitat destruction and human objects. Natural causes of death include adverse temperatures, predation by crocodiles on young, and disease.


Ship strikes

Their slow-moving, curious nature, coupled with dense coastal development, has led to many violent collisions with propeller-driven boats and ships, leading frequently to maiming, disfigurement, and even death. As a result, a large proportion of manatees exhibit spiral cutting propeller scars on their backs, usually caused by larger vessels that do not have skegs in front of the propellers like the smaller outboard and inboard-outboard recreational boats have. They are now even identified by humans based on their scar patterns. Many manatees have been cut in two by large vessels like ships and tug boats, even in the highly populated lower St. Johns River's narrow channels. Some are concerned that the current situation is inhumane, with upwards of 50 scars and disfigurements from vessel strikes on a single manatee. Often, the lacerations lead to infections, which can prove fatal. Internal injuries stemming from being trapped between hulls and docks and impacts have also been fatal. Recent testing shows that manatees may be able to hear speed boats and other watercraft approaching, due to the frequency the boat makes. However, a manatee may not be able to hear the approaching boats when they are performing day-to-day activities or distractions. The manatee has a tested frequency range of 8 to 32 kilohertz. Manatees hear on a higher frequency than would be expected for such large marine mammals. Many large boats emit very low frequencies, which confuse the manatee and explain their lack of awareness around boats. The Lloyd's mirror effect results in low frequency propeller sounds not being discernible near the surface, where most accidents occur. Research indicates that when a boat has a higher frequency the manatees rapidly swim away from danger. In 2003, a population model was released by the
United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...
that predicted an extremely grave situation confronting the manatee in both the Southwest and Atlantic regions where the vast majority of manatees are found. It states, According to marine mammal
veterinarian A veterinarian (vet), also known as a veterinary surgeon or veterinary physician, is a medical professional who practices veterinary medicine. They manage a wide range of health conditions and injuries in non-human animals. Along with this, vet ...
s: These veterinarians go on to state: One quarter of annual manatee deaths in Florida are caused by boat collisions with manatees. In 2009, of the 429 Florida manatees recorded dead, 97 were killed by commercial and recreational vessels, which broke the earlier record number of 95 set in 2002.


Red tide

Another cause of manatee deaths are red tides, a term used for the proliferation, or "blooms", of the microscopic marine algae ''
Karenia brevis ''Karenia brevis'' is a microscopic, single-celled, photosynthetic organism in the genus '' Karenia''. It is a marine dinoflagellate commonly found in the waters of the Gulf of Mexico. It is the organism responsible for the "Florida red tides" ...
''. This
dinoflagellate The dinoflagellates ( Greek δῖνος ''dinos'' "whirling" and Latin ''flagellum'' "whip, scourge") are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered algae. Dinoflagellates are ...
produces brevetoxins that can have toxic effects on the
central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...
of animals. In 1996, a red tide was responsible for 151 manatee deaths in Florida. The bloom was present from early March to the end of April and killed approximately 15% of the known population of manatees along South Florida's western coast. Other blooms in 1982 and 2005 resulted in 37 and 44 deaths, respectively.


Starvation

In 2021 a massive die-off of
seagrass Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families ( Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the ...
along the
Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...
coast of
Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and ...
left manatees without enough food to eat. As a result of this ecological disaster Florida's manatees began dying at an alarming rate, largely from
starvation Starvation is a severe deficiency in caloric energy intake, below the level needed to maintain an organism's life. It is the most extreme form of malnutrition. In humans, prolonged starvation can cause permanent organ damage and eventually, de ...
. In early 2022 the U.S. Fish and Wildlife Service began a feeding program to address the situation by distributing 3,000 pounds (1,361 kg) of lettuce per day to save the malnourished animals.


Additional threats

Manatees can also be crushed and isolated in water control structures (navigation locks, floodgates, etc.) and are occasionally killed by entanglement in fishing gear, such as crab pot float lines, box traps, and shark nets. While humans are allowed to swim with manatees in one area of Florida, there have been numerous charges of people harassing and disturbing the manatees. According to the United States Fish and Wildlife Service, approximately 99 manatee deaths each year are related to human activities. In January 2016, there were 43 manatee deaths in Florida alone.


Conservation

All three species of manatee are listed by the
World Conservation Union The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natur ...
as vulnerable to extinction. However, The U.S. Fish and Wildlife Service (FWS) does not consider the West Indian manatee to be "endangered" anymore, having downgraded its status to "threatened" as of March 2017. They cite improvements to habitat conditions, population growth and reductions of threats as reasoning for the change. The reclassification was met with controversy, with Florida congressman
Vern Buchanan Vernon Gale Buchanan ( ; born May 8, 1951) is an American businessman and politician serving as the U.S. representative for Florida's 16th congressional district since 2013. A member of the Republican Party, he first entered Congress in 2007, rep ...
and groups such as the Save the Manatee Club and the Center for Biological Diversity expressing concerns that the change would have a detrimental effect on conservation efforts. The new classification will not affect current federal protections. West Indian manatees were originally classified as endangered with the 1967 class of endangered species. Manatee population in the United States reached a low in the 1970s, during which only a few hundred individuals lived in the nation. As of February 2016, 6,250 manatees were reported swimming in Florida's springs. It is illegal under federal and Florida law to injure or harm a manatee. There are many conservation programs that have been created to help manatees.
Save the Manatee Club Save the Manatee (SMC) is a 501(c)(3) non-profit group and membership organization dedicated to the conservation of manatees. The organization was founded in 1981 by singer and songwriter Jimmy Buffett, and Governor of Florida (and later U.S. Se ...
is a non-profit group and membership organization that works to protect manatees and their aquatic ecosystems. Founded by
Bob Graham Daniel Robert "Bob" Graham (born November 9, 1936) is an American lawyer, author, and politician who served as the 38th governor of Florida from 1979 to 1987 and a United States senator from Florida from 1987 to 2005. He is a member of the De ...
, former Florida governor, and singer/songwriter
Jimmy Buffett James William Buffett (born December 25, 1946) is an American singer-songwriter, musician, author, and businessman. He is best known for his music, which often portrays an "island escapism" lifestyle. Together with his Coral Reefer Band, Buffe ...
, this is today's leading manatee conservation club. The MV ''Freedom Star'' and MV ''Liberty Star'', ships used by
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedin ...
to tow Space Shuttle Solid Rocket Boosters back to
Kennedy Space Center The John F. Kennedy Space Center (KSC, originally known as the NASA Launch Operations Center), located on Merritt Island, Florida, is one of the National Aeronautics and Space Administration's (NASA) ten field centers. Since December 196 ...
, were propelled only by water jets to protect the endangered manatee population that inhabits regions of the
Banana River The Banana River is a lagoon that lies between Cape Canaveral and Merritt Island in Brevard County, Florida in the United States. It is part of the Indian River Lagoon system, and connects at its south end to the Indian River; it is the only ...
where the ships are based. Brazil outlawed hunting in 1973 in an effort to preserve the species. Deaths by boat strikes are still common. Although countries are protecting Amazonian manatees in the locations where they are endangered, as of 1994 there were no enforced laws, and the manatees were still being captured throughout their range.


Captivity

There are a number of manatee rehabilitation centers in the United States. These include three government-run critical care facilities in Florida at Lowry Park Zoo,
Miami Seaquarium The Miami Seaquarium is a oceanarium located on the island of Virginia Key in Biscayne Bay, Miami-Dade County, Florida located near downtown Miami. Founded in 1955, it is one of the oldest oceanariums in the United States. In addition to mari ...
, and SeaWorld Orlando. After initial treatment at these facilities, the manatees are transferred to rehabilitation facilities before release. These include the
Cincinnati Zoo and Botanical Garden The Cincinnati Zoo & Botanical Garden is the sixth oldest zoo in the United States, founded in 1873 and officially opening in 1875. It is located in the Avondale neighborhood of Cincinnati, Ohio. It originally began with in the middle of the c ...
, Columbus Zoo and Aquarium,
Epcot Epcot, stylized in all uppercase as EPCOT, is a theme park at the Walt Disney World Resort in Bay Lake, Florida. It is owned and operated by The Walt Disney Company through its Parks, Experiences and Products division. Inspired by an unre ...
's The Seas, South Florida Museum, and
Homosassa Springs Wildlife State Park Homosassa Springs Wildlife State Park is located near Homosassa Springs, Florida, in the United States. The park is one of the notable locations in the state to view manatees. Visitors can get close to the animals on a floating observatory. Bl ...
. The Columbus Zoo was a founding member of the Manatee Rehabilitation Partnership in 2001. Since 1999, the zoo's Manatee Bay facility has helped rehabilitate 20 manatees. The Cincinnati Zoo has rehabilitated and released more than a dozen manatees since 1999. Manatees can also be viewed in a number of European zoos, such as the
Tierpark Berlin The Tierpark Berlin is one of two zoos located in Berlin, Germany. It was founded in 1955 and is located in Friedrichsfelde on the former grounds of Friedrichsfelde Palace, which is situated within the zoo. , the zoo houses 7,250 animals from ...
and the Nuremberg Zoo in Germany, in
ZooParc de Beauval The ZooParc de Beauval (), more commonly called Beauval Zoo or, more simply, Beauval, is a French zoological park located in Saint-Aignan-sur-Cher, Centre-Val de Loire. It features more than 35,000 animals on 40 hectares, which is one of the larges ...
in France, the Aquarium of Genoa in Italy and the Royal Burgers' Zoo in Arnhem, the Netherlands, where manatees have parented offspring. The River Safari at
Singapore Singapore (), officially the Republic of Singapore, is a sovereign island country and city-state in maritime Southeast Asia. It lies about one degree of latitude () north of the equator, off the southern tip of the Malay Peninsula, bor ...
features seven of them. The oldest manatee in captivity was
Snooty Snooty (July 21, 1948 – July 23, 2017) was a male Florida manatee that resided at the Bishop Museum of Science and Nature's Parker Manatee Aquarium in Bradenton, Florida. He was one of the first recorded captive manatee births, and at age 69 ...
, at the South Florida Museum's Parker Manatee Aquarium in
Bradenton, Florida Bradenton ( ) is a city in and the county seat of Manatee County, Florida, United States. As of the 2020 census, the city's population is 55,698. History Late 18th and early 19th centuries A settlement established by Maroons or escaped sl ...
. Born at the Miami Aquarium and Tackle Company on July 21, 1948, Snooty was one of the first recorded captive manatee births. Raised entirely in captivity, Snooty was never to be released into the wild. As such he was the only manatee at the aquarium, and one of only a few captive manatees in the United States that was allowed to interact with human handlers. That made him uniquely suitable for manatee research and education. Snooty died suddenly two days after his 69th birthday, July 23, 2017, when he was found in an underwater area only used to access plumbing for the exhibit life support system. The South Florida Museum's initial press release stated, “Early indications are that an access panel door that is normally bolted shut had somehow been knocked loose and that Snooty was able to swim in.”


Guyana

Since the 19th century,
Georgetown, Guyana Georgetown is the capital and largest city of Guyana. It is situated in Demerara-Mahaica, region 4, on the Atlantic Ocean coast, at the mouth of the Demerara River. It is nicknamed the "Garden City of the Caribbean." It is the retail, adminis ...
has kept West Indian manatees in its botanical garden, and later, its national park. In the 1910s and again in the 1950s,
sugar estate Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose, fructose, and galactose. Compound sugars, also called disaccharides or double ...
s in Guyana used manatees to keep their irrigation canals weed-free. Between the 1950s and 1970s, the Georgetown water treatment plant used manatees in their storage canals for the same purpose.


Culture

The manatee has been linked to folklore on
mermaid In folklore, a mermaid is an aquatic creature with the head and upper body of a female human and the tail of a fish. Mermaids appear in the folklore of many cultures worldwide, including Europe, Asia, and Africa. Mermaids are sometimes asso ...
s. In
West Africa West Africa or Western Africa is the westernmost region of Africa. The United Nations defines Western Africa as the 16 countries of Benin, Burkina Faso, Cape Verde, The Gambia, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Liberia, Mali ...
n folklore, they were considered sacred and thought to have been once human. Killing one was
taboo A taboo or tabu is a social group's ban, prohibition, or avoidance of something (usually an utterance or behavior) based on the group's sense that it is excessively repulsive, sacred, or allowed only for certain persons.''Encyclopædia Britannica ...
and required penance. In the novel '' Moby-Dick'', Herman Melville distinguishes manatees ("Lamatins", cf. '' lamatins'') from small whales; stating, "I am aware that down to the present time, the fish styled Lamatins and Dugongs (Pig-fish and Sow-fish of the Coffins of Nantucket) are included by many naturalists among the whales. But as these pig-fish are a noisy, contemptible set, mostly lurking in the mouths of rivers, and feeding on wet hay, and especially as they do not spout, I deny their credentials as whales; and have presented them with their passports to quit the Kingdom of Cetology." A manatee called Wardell appears in the Animal Crossing: New Horizons video game. He is part of a paid downloadable content expansion, managing and selling furniture to the player.


See also

* Dwarf manatee *
Manatee of Helena The Manatee of Helena is a creature believed to have once inhabited the coast of Saint Helena, an island supposed to be largely populated by manatee Manatees (family Trichechidae, genus ''Trichechus'') are large, fully aquatic, mostly herbivo ...


References


Further reading

*


External links


Save the Manatee

Murie, James ''On the Form and Structure of the Manatee'' (''Manatus americanus''), (1872) London, Zoological Society of London Year

Florida Fish and Wildlife Conservation Commission

Reuters: Florida manatees may lose endangered status





''Bibliography and Index of the Sirenia and Desmostylia'' – Dr. Domning's authoritative manatee research bibliography
{{Authority control Sirenians Mammal families Extant Pleistocene first appearances Taxa named by Carl Linnaeus Taxa named by Theodore Gill