African manatee (Trichechus senegalensis)
|Also known as:||seacow, West African manatee|
|French:||Lamantin D'Afrique, Lamantin Du Sénégal|
|Spanish:||Manatí De Senegal|
|Size||Length: 3 – 4 m (2)|
|Weight||up to 500 kg (2)|
Classified as Vulnerable (VU) on the IUCN Red List 2007 (1) and listed on Appendix II of CITES (3).
The African manatee is the least known of all the Sirenians (4); the unique group of manatees and dugongs that are the only herbivorous marine mammals in existence (5). Despite their strange, seemingly cumbersome, cow-like appearance, they are perfectly suited to their aquatic habitat, with a stream-lined, spindle-shaped body; a tail flattened horizontally like a spatula; and forelimbs, bearing nails, that act as paddles. The skin of the African manatee is greyish-brown, finely wrinkled, and sparsely covered with fine, colourless hairs (2). These hairs, and the stout bristles around the mouth, are the reason for the scientific name Trichechus, meaning “to have hair” in Greek (6)
Occurs in rivers, estuaries and coastal regions of West Africa, from Senegal, to Gabon and Angola (2).
The African manatee inhabits shallow coastal waters and rivers (2), moving freely between salt and freshwater (1), but seems to prefer large, shallow estuaries and weedy swamps (2).
These gentle herbivores feed on plants growing within the water, and occasionally on the leaves of mangroves hanging over the water’s edge (2), using their flexible flippers and bristly lips to push the vegetation into their mouths (6). African manatees consume such vast quantities of aquatic vegetation, maybe around 8,000 kilograms each year, that they have even been suggested as a natural method of aquatic weed control! (2). The large intestine of manatees is suitably enormous, sometimes up to 20 metres in length, in order to digest these great quantities (6). Even though the African manatee shares its habitat with sharks and crocodiles, humans are its only known predator (2).
The social structure of the African manatee is little-known; it was once believed to be a monogamous animal, living in groups of an adult pair with their calves; however now it is thought more likely that the only strong bond is between a female and her calf (2). Like other manatees, the African species is believed to form large mating herds, consisting of a female in oestrus and several males, remaining together for up to a month. Within the month, the female is only receptive to mating for a day or two, during which time the males will shove and push each other in an effort to mate with the female, and the female will mate with several males (6). The African manatee gives birth to a single calf at a time, in a weedy swamp or shallow lagoon (2). The metre long newborn remains with its mother, swimming close by her side, for the first one to two years of its life (6).
Local hunting of African manatees for their palatable meat and their skin, bones and oil has been significant, causing population declines in certain areas (1) (2). Although illegal, hunting is still a common practice all over West Africa (4), but its impact on the species is hard to determine as hunting is carried out secretively by people in fear of prosecution (2).
A further threat to the African manatee is entanglement in fishing nets. In Guinea-Bissau, this is the most immediate threat to the manatee population. Sometimes, the accidentally caught animals are butchered, and even if the manatee escapes from the net alive, injuries from the entanglement may result in death later on (4). Not only are the African manatees threatened by entanglement, but the damage done to the nets in such situations has, in some areas (such as Sierra Leone), instigated people to hunt manatees, reducing their numbers in an attempt to lessen the chance of costly damage being done again (6). Similarly, conflict arises between manatees and humans when, during the rainy season, manatees roam into rice fields, destroying precious crops (4) (6).
The African manatee is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), meaning that any trade in this species should be carefully monitored (3), and it is also protected by national laws in all countries in which it occurs (1). However, this important legal protection lacks the support of enforcement and education (1) (2), and it is thought that hunting continues at unsustainable levels (1). The African manatee may gain a degree of protection within the several protected areas it occurs in, including Basse Casamance National Park, Senegal; Digya National Park, Ghana and Iles Eotiles National Park, Côte d'Ivoire (1), but further action to reduce hunting and entanglement is critical to ensure the future of this fascinating gentle giant.
For further information on the African manatee see:
EDGE of Existence:
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- Herbivores: animals that consume only vegetable matter.
- Monogamous: having only one mate during a breeding season, or throughout the breeding life of a pair.
- Oestrus: the time of ovulation (release of an egg from the ovary) in female mammals, when the female becomes receptive to males, also known as ‘heat’.
IUCN Red List (October, 2007)
- Husar, S.L. (1978) Trichechus senegalensis. Mammalian Species, 89: 1 - 3.
CITES (October, 2007)
- Silva, M.A. and Araújo, A. (2001) Distribution and current status of the West African manatee (Trichechus senegalensis) in Guinea-Bissau. Marine Mammal Science, 17(2): 418 - 424.
- Domning, D.P. (2002) Sirenian Evolution. In: Perrin, W.F., Würsig, B. and Thewissen, J.G.M. (Eds) Encylopedia of Marine Mammals. Academic Press, London.
- Reynolds III, J.E. and Powell, J.A. (2002) Manatees. In: Perrin, W.F., Würsig, B. and Thewissen, J.G.M. (Eds) Encylopedia of Marine Mammals. Academic Press, London.