The African manatee (Trichechus senegalensis), also called the West African manatee, is a type of manatee that lives in many areas of Western Africa, from Senegal to Angola. It is the only manatee species found in the Old World. It is also one of the two living Sirenians in the Old World, with the other being the dugong.
Taxonomy
The African manatee was given the scientific name Trichechus senegalensis in 1795 by scientist Johann Heinrich Friedrich Link. No subspecies of this species are known. Although African manatees live in coastal areas and inland regions, genetic studies show the populations are similar. The African manatee belongs to the Trichechus genus, which includes two other species: the Amazonian manatee and the West Indian manatee. These animals are part of a group of aquatic mammals called sirenians.
Range and habitat
African manatees live in the most varied types of habitats among all manatee species. They can be found in offshore islands in the Atlantic Ocean, rivers in the western Sahel region, equatorial rainforest rivers, and other areas. It is reported that manatees near the coast move up rivers during the rainy season and return to the coast during the dry season. The movement and habitats of African manatees have been harmed by the construction of agricultural and hydroelectric dams along rivers, which separate manatee populations. Examples include the Akosombo Dam in Ghana, the Diama Dam in Senegal, and the Felou Dam in Mali. These dams have permanently separated manatees from the coast.
African manatees are found in many regions of West Africa, including 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. They live in both brackish (a mix of salt and fresh water) and freshwater environments, such as oceans, rivers, lakes, coastal estuaries, reservoirs, lagoons, and bays. African manatees rarely live in water colder than 18°C (64°F).
Manatees can be found as far as 75 kilometers (47 miles) from the shore in shallow coastal areas with calm mangrove creeks covered in seagrass. Some inland lakes where manatees live include Lake Volta, the Inner Niger River Delta in Mali, Lake Léré, and Lake de Tréné. These lakes often act as safe areas for manatees during the dry season when river water levels drop. Rivers that support manatees stretch from north to south, including the Senegal, Saloum, Gambia, Casamance, Cacheu, Mansôa, Geba, Buba, Tombali, Cacine, Kogon, Konkouré, 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, Ogooué, Lovanzi, Kouilou, Congo, Dande, Bengo, and Cuanza. Manatees travel up these rivers until they reach shallow waters or strong waterfalls that block their path.
The areas with the most manatees include Guinea-Bissau, the lagoons of Côte d'Ivoire, the southern parts of the Niger River in Nigeria, the Sanaga River in Cameroon, the coastal lagoons of Gabon, and the lower sections of the Congo River. A study in Côte d'Ivoire tracked manatees using radio tags to learn where they prefer to live. The study found that most manatees live in coastal lagoons, mangrove areas, and other vegetation-rich environments. They were also found in grassy estuaries of large rivers with mangroves and in protected coastal areas with less than 3 meters (10 feet) of water that contain both mangroves and underwater plants.
Diet
Manatees are omnivores and sometimes eat clams, mollusks, and fish found in fishing nets. The amount of non-plant material in their diet depends on where they live. Manatees that live near the coast eat about 50% non-plant material on average over their lifetime. The West African manatee is the only type of sirenian that intentionally eats non-plant material. Most of the African manatee’s diet includes plants that grow above or hang over water. African manatees in rivers mainly eat plants that grow along the riverbanks. African manatees in estuaries only eat mangrove trees. Each day, an African manatee eats about 4% to 9% of its body weight in wet vegetation. Microorganisms in the African manatee’s long intestine, which can be up to 20 meters (66 feet) in length, help break down the large amount and variety of plants it eats daily.
Description
The African manatee has a body that is widest in the middle, and its tail looks like a paddle. Its body is gray, and it has small, colorless hairs covering its skin. Algae and tiny organisms often grow on its body, making it look brown or greenish at times. Baby manatees are darker in color when they are very young. African manatees can grow up to 4.5 meters (15 feet) long and weigh about 360 kilograms (790 pounds). They usually move very slowly, traveling 4.8 to 8.0 kilometers (3 to 5 miles) per hour. However, when they are scared by predators, they can swim faster, reaching speeds of about 32 kilometers (20 miles) per hour. The manatee’s large front flippers are used to swim and bring food to its mouth. It chews food with strong molars, which are its only teeth. When a manatee is born, it has two small, early teeth in each jaw, but it loses these as it grows. If its molars are lost, new ones grow in their place. The manatee’s flippers, which have nails, are also used to touch other manatees. African manatees do not have hind limbs. From the outside, they look similar to American manatees, but they are different from Amazonian manatees, which have white markings on their stomachs.
Evolution and legends
The West African manatee is related to manatees that lived in coastal South America during the Pliocene Epoch. These manatees usually live in freshwater, but scientists believe that ocean currents helped them travel to West Africa during the late Pliocene. The manatee’s appearance may be influenced by these currents and the movement of species over time. The ancestors of the African manatee passed on traits that helped them move and find food. African manatees do not live in only one area and do not depend on a single ecosystem for survival. This diversity may help them survive better. They are more varied than other manatees because they can live in saltwater, though they still need fresh water to drink.
In West Africa, people tell stories about Maame Water (also spelled Mami Wata), a sea goddess who is a symbol of wealth and beauty. She is said to capsize canoes and invite people to her underwater world. Scientists from the Institute of Aquatic Biology and the Wildlife Department in Ghana believe Maame Water is inspired by the West African manatee. Dr. Mamaa Entsua-Mensah, a researcher, explains that female manatees look like goddesses when they surface for air. The shape of their bodies can make them appear like a woman with fish-like features.
Among the Serer people of Senegal, the Gambia, and Mauritania, the manatee is considered sacred and highly respected. In their creation myth, the manatee is seen as the guardian of the secrets of the future.
Behavior
The African manatee is active at night. They move quietly, eat, and are most active during the evening and nighttime. During the day, they rest in shallow water that is 1 to 2 meters deep. In countries like Sierra Leone, African manatees move upstream when rivers flood in June and July. This flooding can reduce the amount of food available and make the water less salty. African manatees live in small groups of 1 to 6. They have few natural predators, including sharks and crocodiles. They are also social animals, spending much of their time bonding through touch, verbal communication, and smell. This helps them form strong friendships. When weather changes, manatees travel in larger groups to find warmer water and more food.
Reproduction
The sex of an African manatee can only be identified by carefully examining the area under its body. The only visible difference between males and females is the location of their genital openings. However, males are generally smaller than females. Some female African manatees can become sexually mature as early as 3 years old and give birth every 3 to 5 years during their estimated 30-year lifespan. Males take longer to mature, usually reaching sexual maturity around 9 to 10 years old, and rarely can fertilize an egg at 2 or 3 years old. African manatees can breed anytime during the year. When males and females mate, they do not form monogamous pairs; typically, several males will mate with one female. When competing for the chance to mate, males may push and shove each other. Female African manatees give birth to one calf at a time after a pregnancy lasting about 13 months. Calves are able to swim on their own immediately after birth. Although the social structure of African manatees is not fully understood, research suggests that the strongest and most consistent relationships are between a mother and her calf.
Threats
The African manatee is in danger because people hunt them for their meat, oil, bones, and skin. These items are valuable to poachers. The oil is used to make walking sticks and toy spinning tops. In some countries, like Nigeria and Cameroon, manatees are sold to zoos, aquariums, and online as pets. They are sometimes sent to other countries. Visitors to these areas may see manatee meat for sale in markets. However, weak laws and poor enforcement allow poachers to avoid punishment. In countries such as Mali and Chad, people use manatee oil to treat health issues like ear infections, joint pain, and skin problems.
Other threats to manatees include human activities that harm their environment. Building cities, farms, and dams, as well as using more hydroelectric power in countries like Côte d'Ivoire and Ghana, destroy manatee habitats. Dams have caused some manatee groups to become separated from others, which may affect their survival. At dams such as the Kanji Dam on the Niger River and the Akosombo Dam on the Volta River, manatees have been injured or killed by turbines and intake systems. Heavy boat traffic increases the risk of manatees colliding with vessels. Natural events, like droughts and changes in water levels, can leave manatees stranded in areas where they cannot survive. Some are accidentally killed by fishing nets and trawls meant for catching sharks.
Manatees sometimes act in ways that lead humans to hunt them. When they get tangled in fishing nets, they can damage the nets. In countries like Sierra Leone, people believe killing manatees reduces the need to repair expensive nets. Manatees also harm rice crops by entering fields during rainy seasons.
Many manatees that travel up the Niger River die from starvation. The river dries up during hot, dry periods, but manatees often move there during the rainy season. When the water disappears, they cannot reach other water sources.
Manatees have few natural predators. Sharks and crocodiles sometimes hunt them, but this is rare because manatees and these animals live in different areas. In West Africa, crocodiles are the main natural predators of manatees, aside from humans.
Conservation
From November 2004 to December 2007, the West African Manatee Conservation Project completed Phase I. During this time, people in six African countries—Mauritania, Senegal, The Gambia, Guinea, Guinea-Bissau, and Sierra Leone—gathered new information about the African manatee. They collected data on the manatee’s population, the value of the species, and the areas where it lives by conducting surveys in their countries. Other African nations also shared reports that helped increase understanding of the manatee. Because of this work, the public, children, and scientists now have better information about how to protect the African manatee. Fieldwork during Phase I also allowed researchers to closely study the manatee’s daily life and habits.
Because Phase I was successful, Wetlands International will begin Phase II. In this phase, the information collected during Phase I will be shared more widely in the areas where the manatee lives. Phase II will continue research and work to improve laws and education about manatees.
The African manatee is listed on Appendix I of the Convention on International Trade in Endangered Species (CITES), which means international trade in the species is strictly controlled. Laws exist in every country where the manatee lives to protect it, but these laws are not always followed. Without proper enforcement and education, the manatee’s population continues to decrease.