African manatee

African manatee
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Class: Mammalia
Order: Sirenia
Family: Trichechidae
Genus: Trichechus
Species: T. senegalensis
Binomial name
Trichechus senegalensis
Link, 1795
African manatee range

The African manatee (Trichechus senegalensis), also known as the West African manatee or seacow, is a species of manatee; it is mostly herbivorous (eats plants). African manatees can be found in much of the western region of Africa, from Senegal to Angola.[2] Scientists do not know a lot about this species, but they hypothesize the African manatee is very similar to the West Indian manatee (Trichechus manatus).[3]

Taxonomy

The African manatee was officially declared a species under the Trichechus senegalensis taxon in 1795 by the naturalist, Johann Heinrich Friedrich Link. No subspecies of this taxon are known, but unreliable claims have been made that there are morphological disparities between coastal manatee populations and isolated inland populations. After more research, no genetic evidence supports these claims and form any subspecies.[1] The African manatee falls under the genus Trichechus with only two other species, the Amazonian manatee and the West Indian manatee, which are also sirenians.[4]

Range and habitat

African manatees can be found in much of the western region of Africa such as in Angola, Benin, Cameroon, Chad, the Republic of the Congo, the Democratic Republic of the Congo, Côte d'Ivoire, Equatorial Guinea, Gabon, The Gambia, Ghana, Guinea, Guinea-Bissau, Liberia, Mali, Mauritania, Niger, Nigeria, Senegal, Sierra Leone and Togo. Not only are these manatees found in many countries, but also in bodies of water ranging from brackish to freshwater. They can be found in oceans, rivers, lakes, coastal estuaries, reservoirs, lagoons, and calm shallow bays on the coast.[1] However, a limiting factor of where the African manatee can live is temperature. It is very rare to find an African manatee in water with a temperature below 18 °C (64 °F).[5]

Some are located along the west coast of Africa, in the southeastern and central eastern waters of the Atlantic Ocean. Manatees have been found as far offshore as 75 kilometres (47 mi) out, where there are shallow coastal flats and calm mangrove creeks filled with seagrass. Lakes where they dwell include Lake Volta, Inner Niger River Delta in Mali, Lake Léré, and Lake de Tréné. Due to fluctuating flow rates and water levels in rivers, some of these permanent lakes serve as refuges, during the dry season, to manatees in connecting rivers. From north to south, the river systems that they can be found include the Senegal, Saloum, Gambia, Casamance, Cacheu, Mansôa, Geba, Buba, Tombali, Cacine, Kogon, Kondoure, Sierra Leone, Great Scarcies, Little Scarcies, Sherbro, Malem, Waanje, Sewa, Missunado, Cavalla, St. Paul, Morro, St. John, Bandama, Niouniourou, Sassandra, Comoé, Bia, Tano, Volta, Mono, Oueme, Niger, Mekrou, Benue, Cross, Katsena Ala, Bani, Akwayafe, Rio del Rey, Ngosso, Andokat, Mene, Munaya, Wouri, Sanaga, Faro, Chari, Bamaingui, Bahr-Kieta, Logoné, Mitémélé, Gabon, Ogoué, Lovanzi, Kouilou, Congo, Dande, Bengo, and Cuanza. They go up these rivers until they are unable to proceed due to water that is too shallow for them to swim through or strong waterfalls they cannot pass.[1]

Both African and West Indian manatees need habitats with protected water and access to food and fresh water. They occasionally journey to less-sheltered areas. Of all of their habitats in Africa, the most populated areas seem to be Guinea-Bissau, the lagoons of Côte d'Ivoire, the southern portions of the Niger River in Nigeria, Sanaga River in Cameroon, coastal lagoons in Gabon, and the lower parts of the Congo River. A study was done in Côte d'Ivoire to find where most African manatees favoured living. They were radio-tagged and tracked, and then they were sighted the most in coastal lagoons with plenty of their main food source, mangroves and other herbaceous growths. They were also found in grass-lined estuaries of big rivers with plenty of mangroves, and in protected coastal spots with less than 3 metres (10 ft) of water, again, with bountiful mangroves and also marine macrophytes.[1]

Diet

Although generally speaking, manatees are herbivores, the African manatee also eats clams, mollusks, and fish they find in nets. The majority of the diet of the African manatee is composed of many different types of flora found above or hanging over the water, instead of submerged. African manatees inhabiting rivers eat mostly overhanging plants growing on the river banks. The diets of African manatees living in estuaries consist of just mangrove trees. Each day, the African manatee will eat about 4 to 9 percent of its body weight in wet vegetation.[2][3] Microorganisms in the African manatee's long large intestine (which measures up to 20 metres or 66 feet in length) aid the manatee in digesting the large quantity and variety of vegetation it takes in every day.[5]

Description

African manatee on land

The shape of an African manatee's body is such that it is "full around the middle and narrowing to a paddle-shaped tail". It is grey in colour, with small, colourless hairs around its body. However, algae and other tiny organisms often grow on them, so they appear brown or greenish. Calves, however, are darker in colour when they are very young.[2][5][6] In length, African manatees measure up to 4.5 m (14.6 ft), and they weigh about 360 kg (790 lb).[3] African manatees are extremely slow, moving at between 4.8 and 8.0 km (3 and 5 mi) an hour, unless they fear predators, when they can travel at speeds of about 32 km (20 mi) an hour. The African manatee's large forelimbs, or flippers, are used to paddle and to bring food to the manatee's mouth, after which the vegetation is chewed by its strong molars, which are the only teeth it has. Each jaw has two vestigial incisors when the manatee is born, which it loses as it matures.[6] If the African manatee's molars happen to fall out, new molars grow in their place. The manatee's flippers, which bear nails, are also used "to embrace and touch other manatees". The African manatee does not have any hindlimbs.[5][7][8][9] By looking at the exterior of the African manatee, one would not be able to distinguish it from the American manatee, however it is different from the Amazonian manatee, which has characteristic white markings on its abdomen.[8]

Evolution and legends

A form descendents of "coastal South American trichechids" of the late time of Pliocene is believed to have "reached West Africa by way of transoceanic currents, perhaps since the late Pliocene, to give rise to the West African manatee."[10]

According to people of western Africa, Maame (also spelled Mami) Water, a recurring character in many coastal legends, is a goddess of the sea, and a symbol of wealth and beauty. Contrasting with this depiction, Maame Water also flips over canoes and entices their occupants to come "down to her watery kingdom". Scientists from the Institute of Aquatic Biology of the Centre for Scientific and Industrial Research (CSIR) and the Wildlife Department in Ghana have drawn the conclusion that Maame Water is not a sea goddess, in fact, but the West African manatee. According to Dr. Mamaa Entsua-Mensah, who performs research for CSIR, "the female manatee looks like a woman when they [sic] surface to inhale fresh air at night." Entsua-Mensah said "because of the breast with teats, when people sight the mammals jumping out of the sea in the night to take in long deep breath of air, they are perceived as half woman, half fish." It was not allowed to openly speak of the sacred goddess Maame Water except after certain rituals. In Nigeria, stories are passed through generations concerning "persons whose fortunes have changed dramatically when they married Maame Water, the mermaid, but lost everything when they became unfaithful to her".[11]

Behaviour

The African manatee is nocturnal, tending to travel silently, eat, and be active towards the end of the day and the nighttime. During the daytime, the African manatee dozes in shallow (1–2 m deep) water. In countries such as Sierra Leone, African manatees are known to migrate upstream when flooding occurs in June and July. This flooding can lower the availability of food for the manatees and the salinity of waterways.[3] African manatees live in groups of one to six individuals. One reason for the African manatee living in small groups is it has very few natural predators, two of which are sharks and crocodiles.[5][12]

Reproduction

One cannot tell the sex of an individual African manatee without closely examining the manatee's underside. The only visible distinctions between males and females are the genital openings. However, males tend to be smaller than females. Some female African manatees are sexually mature as young as three years of age, and they give birth every three to five years of their estimated 30-year life span. Males take a much longer time to mature, about 9 to 10 years. Rarely will a male African manatee be able to fertilise an egg at two or three years old. African manatees breed at all times of the year. When males and females mate, it is not for life; multiple males will usually mate with one female.[2][6] Males fight with each other by pushing and shoving when the opportunity to mate with a female is at stake. Female African manatees give birth to one calf at a time after being pregnant for about 13 months, and calves can swim on their own at birth. Although the African manatee's social organisation is not well known, research has shown the most common and tightly knit bonds are between a mother and her calf.[5]

Threats

The African manatee has become a vulnerable species because its meat, oil, bones (used to make walking stick handles and "spinning-tops used in a local game called cii"), and skin can bring great wealth to poachers. In some countries, such as Nigeria and Cameroon, African manatees are sold to zoos, aquariums, and online as pets, sometimes being shipped internationally. Anyone visiting such countries would easily notice the manatee meat being sold on the streets and marketplaces, but the lack of law enforcement prevents the poachers from being punished. Residents of countries such as Mali and Chad depend on the oil of the African manatee to cure ailments such as ear infections, rheumatism, and skin conditions.[1]

Urban and agricultural development, increased damming, and increased use of hydroelectric power in rivers in countries such as Côte d'Ivoire and Ghana are more threats to the African manatee's habitat and life, and thick congestion of boats in waterways may cause them to have a deadly run-in with the vessels. However, even natural occurrences, such as droughts and tidal changes, often strand manatees in an unsuitable habitat, and some are killed accidentally by fishing trawls and nets intended for catching sharks.[1]

Some behaviours of African manatees provoke humans' desires to hunt them. When they get tangled up in fishing nets, the animals can do damage to the nets. People in countries such as Sierra Leone feel if they kill and therefore reduce the number of African manatees, the chances of their nets requiring expensive repairs will be lessened. In addition, African manatees have been known to destroy rice crops by drifting into fields during the rainy season, which is another reason for humans to want to kill them.[13]

Conservation

From November 2004 until December 2007, the West African Manatee Conservation Project completed Phase I. During this phase, residents of six African countries (Mauritania, Senegal, The Gambia, Guinea, Guinea Bissau and Sierra Leone) put together a database of previously unknown information about the species (such as population, economic value, and habitat range) by conducting surveys in their countries. Other African countries also contributed reports that broadened knowledge of the African manatee. Because of the work done during this phase, the general public, young children, and experienced scientists alike are receiving better information than ever before as to how to protect the African manatees. Phase I also allowed for up-close examination of the African manatee's way of life through field work.

Due to the large-scale success of Phase I, a Phase II is to be enacted by Wetlands International. During Phase II, the information collected in Phase I will be even more widely distributed around the areas in which the African manatee lives, and the second phase will focus on "improving legislation and developing research, communication, and education." [14]

"The African manatee is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES)", which states that trade in any species on the list is to be very carefully watched out for and terminated. Laws protect the African manatee in every country in which it lives. However, laws will do nothing if they are not enforced, which is unfortunately the case with the African manatee. Due to mass lack of enforcement and education, the African manatee population is still being steadily depleted.[5]

References

  1. 1 2 3 4 5 6 7 Powell, J.; Kouadio, A. (2008). "Trichechus senegalensis". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. Retrieved November 11, 2011.
  2. 1 2 3 4 "Manatee". Sea World. December 30, 2011. Retrieved December 30, 2011.
  3. 1 2 3 4 "West African manatee (Trichechus senegalensis)". Animal Corner. 2012. Retrieved January 5, 2011.
  4. ↑ Husar, Sandra L. (6 January 1978). "Trichechus senegalensis" (PDF). Mammalian Species. 2011.2 (The American Society of Mammalogists) 89: 1. doi:10.2307/3503790. Retrieved November 13, 2011.
  5. 1 2 3 4 5 6 7 "Trichechus senegalensis". Encyclopedia of Life. Retrieved January 7, 2011.
  6. 1 2 3 Jefferson, T.A.; Leatherwood, S.; Webber, M.A. "Trichechus senegalensis". nlbif. Retrieved January 8, 2011.
  7. ↑ "West African manatee". Paradise Earth. 2008. Retrieved December 31, 2011.
  8. 1 2 "West African Manatee". Animal Info. 2006. Retrieved January 7, 2011.
  9. ↑ Dr. Macrini, Ted (2004). ""Trichechus senegalensis" (On-line)". Digital Morphology. Archived from the original on 14 December 2010. Retrieved January 8, 2011.
  10. ↑ O'Shea, Thomas J. (July 1994), "Manatees" (PDF), Scientific American: 7
  11. ↑ "West African Manatee". Sirenian International, Inc. 2002. Retrieved January 8, 2011.
  12. ↑ "Manatee Predators". Infoqis Publishing, Co. 2009. Retrieved January 7, 2011.
  13. ↑ "African manatee (Trichechus senegalensis)". Wildscreen. 2011. Retrieved December 30, 2011.
  14. ↑ Dr. Dagou, Mame; Greatrix, Emma (November 3, 2007), Conservation Prospects for the West African Manatee, retrieved January 8, 2011

Bibliography

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