Amazonian manatee

Last updated

Contents

Amazonian manatee [1]
Amazonian manatee (Trichechus inunguis).jpg
CITES Appendix I (CITES) [3]
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Sirenia
Family: Trichechidae
Genus: Trichechus
Species:
T. inunguis
Binomial name
Trichechus inunguis
(Natterer, 1883)
Amazonian Manatee.png
Amazonian manatee range

The Amazonian manatee (Trichechus inunguis) is a species of manatee that lives in the Amazon Basin in Brazil, Peru, Colombia and Ecuador. [2] It has thin, wrinkled brownish or gray colored skin, with fine hairs scattered over its body and a white chest patch. [4] [5] It is the smallest of the three extant species of manatee. [6]

Taxonomy

The specific name, inunguis is Latin for "nailless". The genus name Trichechus, comes from Latin meaning "hair", referencing the whiskers around the manatee's mouth. [4]

Physical characteristics

The Amazonian manatee is the smallest member of the manatee family and can be distinguished by its smoother rubbery skin and lack of vestigial nails on its flippers. [7] Ranges of body weight and size observed are 7.5–346 kg (17–763 lb) and 76.0–225 cm (2 ft 5.9 in – 7 ft 4.6 in) for captive males, 8.1–379 kg (18–836 lb) and 71.0–266 cm (2 ft 4.0 in – 8 ft 8.7 in) for captive females, and 120.0–270 kg (264.6–595.2 lb) and 162.0–230 cm (5 ft 3.8 in – 7 ft 6.6 in) for free-ranging manatees, respectively. [8] The maximum actual Amazonian manatee weight reported is 379 kilograms (836 lb). [8] Calves of the species are born weighing 10–15 kg (22–33 lb) and 85–105 cm (33–41 in) long. [8] The Amazonian Manatees increase in length approximately 1.6-2.0 mm per day. This length is measured along the curvature of the body so absolute length can differ between individuals. As calves, they gain an average of 1 kilogram per week. [9]

Amazonian manatees are large, cylindrically shaped mammals, with forelimbs modified into flippers, no free hind-limbs, and the rear of the body in the form of a flat, rounded, horizontal paddle. [10] The flexible flippers are used for aiding motion over the bottom, scratching, touching, and even embracing other manatees, and moving food into and cleaning the mouth. [10] The manatee's upper lip is modified into a large bristly surface, which is deeply divided. [10] It can move each side of the lips independently while feeding. [10] The general coloration is grey, and most Amazonian manatees have a distinct white or bright pink patch on the breast. [10]

Amazonian manatees, similar to all living manatee species in the family Trichechidae, have polyphyodont teeth. Their teeth are continuously replaced horizontally from the caudal portion of the jaw to the rostral portion throughout the manatee's life, a unique trait among mammals. Only the closest living relative of order Sirenia, elephants, show a similar characteristic of teeth replacement, but elephants have a limited set of these replacement teeth. As the teeth migrate rostrally in the manatee, the roots will be resorbed and the thin enamel will wear down until the tooth is eventually shed. Referred to as cheek teeth, differentiation of manatee teeth into molars and premolars has not occurred, and manatees additionally do not have incisors or canine teeth. These teeth migrate at a rate of about 1–2 mm/month, based on wear and chewing rates. [11]

The Amazonian manatee lacks nails on its flippers, setting it apart from other manatees. [4] Additionally, Amazonian manatees have a very small degree of rostral deflection (30.4°), which can be used as an indication of where in the water column the animal feeds. A small degree of deflection means that the end of the snout is straighter with regard to the caudal portion of the jaw. Animals with a greater degree of deflection, such as D. dugong at about 70° of deflection, are more of a benthic species, feed on the seafloor, and have snouts that point almost completely ventrally. Only T. senegalensis has a smaller rostral deflection of about 25.8°. This is believed to maximize the efficiency of feeding. A small degree of rostral deflection allows Amazonian manatees to feed more effectively at the surface of the water, where much of their food is found. [12]

Behavior and biology

The Amazonian manatee is the only sirenian that lives exclusively in freshwater habitat. [8] The species relies on changes in the peripheral circulation for its primary mechanism for thermoregulation by using sphincters to deflect blood flow from areas of the body in close contact with water. They also rely on subcutaneous fat to reduce heat loss. [13]

Manatees have nostrils, not blowholes like other aquatic mammals, which close when underwater to keep water out and open when above water to breathe. [14] Although manatees can remain under water for extended periods, surfacing for air about every five minutes is common. [15] [16] The longest documented submergence of an Amazonian manatee in captivity is 14 minutes. [17]

Manatees make seasonal movements synchronized with the flood regime of the Amazon Basin. [7] They are found in flooded forests and meadows during the flood season, when food is abundant. [7] The Amazonian manatee has the smallest degree of rostral deflection (25° to 41°) among sirenians, an adaptation to feed closer to the water surface. [18] It is both nocturnal and diurnal and lives its life almost entirely underwater. [19] Only its nostrils protrude from the surface of the water while it searches river and lake bottoms for vegetation. [19]

The Amazonian and West Indian manatees are the only manatees known to vocalize. They have been observed vocalizing alone and with others, particularly between cows and their calves. [20]

Diet

The manatees themselves feed on a variety of aquatic macrophytes, including aroids (especially Pistia , aka "water lettuce" [19] [21] ), grasses, bladderworts, hornworts, water lilies, and particularly, water hyacinths. [22] They are also known to eat palm fruits that fall into the water. [19] Maintaining a herbivorous diet, the manatee has a similar post-gastric digestive process to that of the horse. [18] The manatee consumes approximately 8% of its body weight in food per day. [18]

During the July–August dry season when water levels begin to fall, some populations become restricted to the deep parts of large lakes, where they often remain until the end of the dry season in March. [7] They are thought to fast during this period, their large fat reserves and low metabolic rates – only 36% of the usual placental mammal metabolic rate – allowing them to survive for up to seven months with little or no food. [7]

Reproduction and lifecycle

The Amazonian manatee is a seasonal breeder with a gestational period of 12–14 months and a prolonged calving period. Most births take place between December and July, with about 63% between February and May, during a time of rising river levels in their native region. [23] After the calf is born, it will begin to eat while staying with its mother for 12 – 18 months. [24]

Wild individuals have a lifespan of about 30 years. [19] The record captive lifespan is 17 years. [25]

Population and distribution

As of 1977 the population count of the Amazonian manatee was estimated to be around 10,000. [7] As of now the total population count is undetermined, however the population trend seems to be decreasing. [7] They are mainly distributed throughout the Amazon River Basin in northern South America, ranging from the Marajó Islands in Brazil through Colombia, Peru, and Ecuador. [7] They are occasionally found overlapping with the West Indian manatee along the coasts of Brazil. [7]

Amazonian manatees occur through most of the Amazon River drainage, from the headwaters, in Colombia, Ecuador and Peru to the mouth of the Amazon (close to the Marajó Island) in Brazil over an estimated seven million square kilometers. [2] However, their distribution is patchy, concentrating in areas of nutrient-rich flooded forest, which covers around 300,000 km2 [2] They also inhabit environments in lowland tropical areas below 300 m asl, where there is large production of aquatic and semi-aquatic plants; they are also found in calm, shallow waters, away from human settlements [2]

The Amazonian manatee is completely aquatic and never leaves the water. [7] It is the only manatee to occur exclusively in freshwater environments. [26] The Amazonian manatee favors backwater lakes, oxbows, and lagoons with deep connections to large rivers and abundant aquatic vegetation [26] They are mainly solitary but sometimes they will gather in small groups consisting of up to eight individuals. [24] They engage in long seasonal movements, moving from flooded areas during the wet season to deep water-bodies during the dry season [2]

Natural predators include jaguars, sharks, and crocodiles. [19]

Illegal hunting

The main threat to the Amazonian manatee is illegal hunting. They are hunted for subsistent and local use, not commercially. The hunting has led to the large decline in the population and low population numbers. Between 1935 and 1954, over 140,000 manatees are estimated to have been killed. Despite the laws in place against hunting, hunting continues to occur even in protected areas. Traditional harpoons are the most common weapon used against the manatees but in Ecuador they are also known to be caught in Arapaima fish traps. [2]

They are mainly hunted for their high value meat but the fat and skin are also used for cooking and in medicines. The meat is sold locally to neighbors or at produce markets. It can be illegally sold as sausage or mixira in public markets in Brazil and Ecuador. Mixira is a meat preserved in its own fat and is expensive which drives the hunters. [2]

Between 2011 and 2015, 195 manatees were killed for meat in a single region of Brazil. In another region, 460 were killed in a protected area between 2004 and 2014. [2]

Conservation

Rehabilitation of an infant at "IBAMA" on Marajo Trichechus inunguis.jpg
Rehabilitation of an infant at "IBAMA" on Marajó

The IUCN red list ranks the Amazonian manatee as vulnerable. Population declines are primarily a result of hunting, as well as calf mortality, climate change, and habitat loss. [2] However, due to their murky water habitat it is difficult to gain accurate population estimates. [2]

There are no national management plans for the Amazonian Manatee, except in Colombia. [2] As of 2008, the INPA takes care of 34 captive manatees and the CPPMA is caring for 31 manatees. [2] The manatee has been protected by Peruvian law since 1973, via Supreme Decree 934-73-AG, prohibiting hunting and commercial use of the manatee. [17]

Hunting remains the largest problem and continues in much of its range, even within reserves. [2] In 1986, it was estimated that the hunting levels in Ecuador were unsustainable and it would be gone from this country within 10–15 years. [22] While hunting still occurs, an increasing risk to its continued survival in Ecuador is now believed to be the risk of oil spills. [2] The oil exploration also means an increase in boat traffic on the rivers. [2]

The Amazonian manatees of Peru have experienced much of their decline due to hunting by human populations for meat, blubber, skin and other materials that can be collected from the manatee. [17] Such hunting is carried out with harpoons, gillnets, and set traps. [17] Much of this hunting occurs in the lakes and streams near the Pacaya-Samiria National Reserve in northeastern Peru. [17] The species is slow-moving, docile, and is often found feeding at the surface of the lakes and rivers it inhabits. [7] Manatees are also at risk from pollution, accidental drowning in commercial fishing nets, and the degradation of vegetation by soil erosion resulting from deforestation. [7] Additionally, the indiscriminate release of mercury in mining activities threatens the entire aquatic ecosystem of the Amazon Basin. [7]

See also

Related Research Articles

<span class="mw-page-title-main">Manatee</span> Genus of mammals

Manatees are large, fully aquatic, mostly herbivorous marine mammals 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 West Indian manatee, and the West African manatee. They measure up to 4.0 metres long, weigh as much as 590 kilograms (1,300 lb), and have paddle-like tails.

<span class="mw-page-title-main">Sirenia</span> Order of aquatic herbivorous mammals

The Sirenia, commonly referred to as sea cows or sirenians, are an order of fully aquatic, herbivorous mammals that inhabit swamps, rivers, estuaries, marine wetlands, and coastal marine waters. The extant Sirenia comprise two distinct families: Dugongidae and Trichechidae with a total of four species. The Protosirenidae and Prorastomidae families are extinct. Sirenians are classified in the clade Paenungulata, alongside the elephants and the hyraxes, and evolved in the Eocene 50 million years ago (mya). The Dugongidae diverged from the Trichechidae in the late Eocene or early Oligocene.

<span class="mw-page-title-main">Dugongidae</span> Family of mammals

Dugongidae is a family in the order of Sirenia. The family has one surviving species, the dugong, one recently extinct species, Steller's sea cow, and a number of extinct genera known from fossil records.

<span class="mw-page-title-main">Trichechidae</span> Family of mammals

Trichechidae is a family of sirenians that includes all living manatees and several extinct genera.

<span class="mw-page-title-main">Desmostylia</span> Extinct order of mammals

The Desmostylia are an extinct order of aquatic mammals native to the North Pacific from the early Oligocene (Rupelian) to the late Miocene (Tortonian). Desmostylians are the only known extinct order of marine mammals.

<i>Hydrodamalis</i> Extinct family of mammals

Hydrodamalis is a genus of extinct herbivorous sirenian marine mammals, and included the Steller's sea cow, the Cuesta sea cow, and the Takikawa sea cow. The fossil genus Dusisiren is regarded as the sister taxon of Hydrodamalis: together, the two genera form the dugong subfamily Hydrodamalinae. They were the largest member of the order Sirenia, whose only extant members are the dugong and the manatees. They reached up to 9 metres (30 ft) in length, making the Steller's sea cow among the largest mammals other than whales to have existed in the Holocene epoch. Steller's sea cow was first described by Georg Wilhelm Steller,

<span class="mw-page-title-main">African manatee</span> Species of mammal

The African manatee, 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 Old World.

<span class="mw-page-title-main">West Indian manatee</span> Species of mammal

The West Indian manatee, also known as the North American manatee, is a large, aquatic mammal native to warm coastal areas of the Caribbean, from the eastern US to northern Brazil. Living alone or in herds, it feeds on underwater plants and uses its whiskers to navigate. It is divided into two endangered subspecies, the Florida manatee in the US and the Antillean manatee in the Caribbean, both of which face pressure from habitat loss, pollution, and other human activity. The West Indian manatee is the largest living member of the sirenians, a group of large aquatic mammals that includes the dugong, other manatees, and the extinct Steller's sea cow.

<span class="mw-page-title-main">Aquatic mammal</span> Mammal that dwells partly or entirely in bodies of water

Aquatic and semiaquatic mammals are a diverse group of mammals that dwell partly or entirely in bodies of water. They include the various marine mammals who dwell in oceans, as well as various freshwater species, such as the European otter. They are not a taxon and are not unified by any distinct biological grouping, but rather their dependence on and integral relation to aquatic ecosystems. The level of dependence on aquatic life varies greatly among species. Among freshwater taxa, the Amazonian manatee and river dolphins are completely aquatic and fully dependent on aquatic ecosystems. Semiaquatic freshwater taxa include the Baikal seal, which feeds underwater but rests, molts, and breeds on land; and the capybara and hippopotamus which are able to venture in and out of water in search of food.

<i>Halitherium</i> Extinct genus of mammals

Halitherium is an extinct dugongid sea cow that arose in the late Eocene, then became extinct during the early Oligocene. Its fossils are common in European shales. Inside its flippers were finger bones that did not stick out. Halitherium also had the remnants of back legs, which did not show externally. However, it did have a basic femur, joined to a reduced pelvis. Halitherium also had elongated ribs, presumably to increase lung capacity to provide fine control of buoyancy. A 2014 review presented the opinion that the genus is dubious.

<span class="mw-page-title-main">Evolution of sirenians</span> Development from a Tethytherian ancestor and radiation of species

Sirenia is the order of placental mammals which comprises modern "sea cows" and their extinct relatives. They are the only extant herbivorous marine mammals and the only group of herbivorous mammals to have become completely aquatic. Sirenians are thought to have a 50-million-year-old fossil record. They attained modest diversity during the Oligocene and Miocene, but have since declined as a result of climatic cooling, oceanographic changes, and human interference. Two genera and four species are extant: Trichechus, which includes the three species of manatee that live along the Atlantic coasts and in rivers and coastlines of the Americas and western Africa, and Dugong, which is found in the Indian and Pacific oceans.

The dwarf manatee is a disputed species of manatee allegedly found in the freshwater habitats of the Amazon, though restricted to one tributary of the Aripuanã River. According to Marc van Roosmalen, the scientist who proposed it as a new species, it lives in shallow, fast-running water, and feeds on different species of aquatic plants from the Amazonian manatee, which prefers deeper, slower-moving waters and the plants found there. The dwarf manatee reportedly migrates upriver during the rainy season when the river floods to the headwaters and shallow ponds. Based on its small range, the dwarf manatee is suggested to be considered critically endangered if indeed a separate species, but is not recognized by the IUCN.

<i>Eotheroides</i>

Eotheroides is an extinct genus of Eocene sirenian. It is an early member of the family Dugongidae, which includes the extant dugong. Fossils have been found from Egypt, India, and Madagascar. Eotheroides was first described by Richard Owen in 1875 under the name Eotherium, which was replaced by the current name in 1899.

<i>Metaxytherium</i> Extinct genus of dugong

Metaxytherium is an extinct genus of dugong that lived from the Oligocene until the end of the Pliocene. Fossil remains have been found in Africa, Europe, North America and South America. Generally marine seagrass specialists, they inhabited the warm and shallow waters of the Paratethys, Mediterranean, Caribbean Sea and Pacific coastline. American species of Metaxytherium are considered to be ancestral to the North Pacific family Hydrodamalinae, which includes the giant Steller's sea cow.

Protosiren is an extinct early genus of the order Sirenia. Protosiren existed throughout the Lutetian to Priabonian stages of the Middle Eocene. Fossils have been found in the far-flung locations like the United States, Africa (Egypt), Europe and Asia.

<i>Nanosiren</i>

Nanosiren garciae is an extinct sirenian dugong that lived in warm shallow seas in what is now Venezuela, approximately 11.610—3.6 Ma during the Miocene and Pliocene. The species is listed in the Paleobiology Database, funded by the Australian Research Council.

<span class="mw-page-title-main">Prorastomidae</span> Extinct family of mammals

Prorastomidae is a family of extinct sirenians from Jamaica, related to the extant manatees and dugong. The family includes the oldest known fossils of Sirenians, represented in two genera:

<span class="mw-page-title-main">Caribbean Manatee Conservation Center</span> Organization to help endangered manatees

The Caribbean Manatee Conservation Center is a research, education, rescue, and rehabilitation partnership established in 2009 in the Caribbean island of Puerto Rico in order to help endangered manatees survive from extinction.

<i>Trichechus hesperamazonicus</i> Extinct species of manatee

Trichechus hesperamazonicus, the western Amazonian manatee, is an extinct species of manatee that lived about 40 thousand years ago in the Madeira River, in the Brazilian state of Rondonia. It is known from this single locality, with possible occurrences in the Brazilian state of Acre.

<i>Sobrarbesiren</i> Extinct sirenian

Sobrarbesiren is a genus of extinct sirenian that lived in the Eocene, about 47 million years ago. The type and only species is S. cardieli, known from a multitude of specimens from the Spanish Pyrenees. Sobrarbesiren was a medium-sized animal, 2.7 m long and still retaining both pairs of limbs. Although initially thought to be amphibious, later studies instead suggest that they would have been fully aquatic and been selective sea grass browsers. Unlike modern dugongs and manatees, they likely lacked a tail fluke, although it would have appeared horizontally flattened.

References

  1. ↑ Shoshani, J. (2005). Wilson, D.E.; Reeder, D.M. (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. p. 93. ISBN   978-0-8018-8221-0. OCLC   62265494.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Marmontel, M.; de Souza, D.; Kendall, S. (2016). "Trichechus inunguis". IUCN Red List of Threatened Species . 2016: e.T22102A43793736. doi: 10.2305/IUCN.UK.2016-2.RLTS.T22102A43793736.en . Retrieved 11 November 2021.
  3. ↑ "Appendices | CITES". cites.org. Retrieved 2022-01-14.
  4. 1 2 3 "Manatees". Canisius Ambassadors for Conservation. Archived from the original on 2010-06-29. Retrieved 2008-11-03.
  5. ↑ Husar, Sandra L. (1977). "Trichechus inunguis". Mammalian Species (72): 1–4. doi:10.2307/3503928. JSTOR   3503928.
  6. ↑ Trials of a Primatologist. - smithsonianmag.com. Accessed March 16, 2008.
  7. 1 2 3 4 5 6 7 8 9 10 11 12 13 "Amazonian manatee (Trichechus inunguis)". edgeofexistence.org. Zoological Society of London. Archived from the original on 10 August 2016. Retrieved 24 October 2014.
  8. 1 2 3 4 Amaral, Rodrigo S.; Silva, Vera M. F. da; Rosas, Fernando C. W. (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. doi:10.1017/S1755267210000886.
  9. ↑ Rosas, Fernando Cesar Weber (1994). "Biology, conservation and status of the Amazonian Manatee Trichechus inunguis". Mammal Review. 24 (2): 49–59. doi:10.1111/j.1365-2907.1994.tb00134.x.
  10. 1 2 3 4 5 "Animal Info - Amazonian Manatee". Animal Info. animalinfo.org. Retrieved 23 October 2014.
  11. ↑ Domning, D.P.; Hayek, L.-A.C. (1984). "Horizontal tooth replacement in the Amazonian manatee (Trichechus inunguis)". Mammalia. 48 (1): 105. doi:10.1515/mamm.1984.48.1.105. S2CID   83985834.
  12. ↑ Domning, D.P.; Morgan, G.S.; Ray, C.E. (1982). "North American Eocene Sea Cows (Mammalia: Sirenia)" (PDF). Smithsonian Contributions to Paleobiology (52): 1–69. doi:10.5479/si.00810266.52.1.
  13. ↑ Gallivan, G. J.; Best, R. C.; Kanwisher, J. W. (1983). "Temperature Regulation in the Amazonian Manatee Trichechus inunguis". Physiological Zoology. 56 (2): 255–262. doi:10.1086/physzool.56.2.30156057. JSTOR   30156057. S2CID   88367955.
  14. ↑ "Facts about Manatees". Manatee World. 2014. Retrieved 8 December 2014.
  15. ↑ "Manatee Trichechus". National Geographic. 11 November 2010. Archived from the original on January 14, 2010. Retrieved 8 December 2014.
  16. ↑ Gallivan, G. J.; Best, R. C. (1980). "Metabolism and Respiration of the Amazonian Manatee (Trichechus inunguis)". Physiological Zoology. 53 (3): 245–253. doi:10.1086/physzool.53.3.30155787. JSTOR   30155787. S2CID   87433725.
  17. 1 2 3 4 5 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.
  18. 1 2 3 Pazin-Guterres, Michelle (2014). "Feeding Ecology of the Amazonian Manatee (Trichechus inunguis) in the Mamirauá and Amanã Sustainable Development Reserves, Brazil". Aquatic Mammals. 40 (2): 139–149. doi:10.1578/AM.40.2.2014.139.
  19. 1 2 3 4 5 6 Gorog, Antonia (1999). "ADW: Trichechus inunguis: INFORMATION". Animal Diversity Web. University of Michigan. Retrieved 9 April 2014.
  20. ↑ Bullock, Theodore H.; Domning, Daryl P.; Best, Robin C. (1980). "Evoked Brain Potentials Demonstrate Hearing in a Manatee (Trichechus inunguis)". Journal of Mammalogy. 61 (1): 130–133. doi:10.2307/1379969. JSTOR   1379969.
  21. ↑ "Amazon manatee | WWF". wwf.panda.org. WWF - World Wide Fund For Nature. 2017. Retrieved 29 March 2018.
  22. 1 2 Timm, Robert M.; Albuja, Luis; Clauson, Barbara L. (1986). "Ecology, Distribution, Harvest, and Conservation of the Amazonian Manatee Trichechus inunguis in Ecuador". Biotropica. 18 (2): 150–156. doi:10.2307/2388757. hdl: 1808/6920 . JSTOR   2388757.
  23. ↑ Best, Robin C. (1982). "Seasonal Breeding in the Amazonian Manatee, Trichechus inunguis (Mammalia: Sirenia)". Biotropica. 14 (1): 76–78. doi:10.2307/2387764. JSTOR   2387764.
  24. 1 2 "Amazonian Manatee". theanimalfiles.com. Retrieved 24 October 2014.
  25. ↑ Morales, Patricia (1986). "The Life and Death of an Amazon Manatee". Proceedings of the International Association of Aquatic Animal Medicine. 1 (3): 43–48.
  26. 1 2 "Arkive closure". Archived from the original on 2015-01-20. Retrieved 2014-10-24.

Further reading

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.