|Scientific Name:||Trichechus senegalensis|
|Species Authority:||Link, 1795|
|Taxonomic Notes:||There are no recognized Trichechus senegalensis subspecies and limited genetic information indicates high genetic diversity (Vianna et al. 2006, Keith Diagne 2014). Anecdotal assertions of morphological differences between isolated inland populations and coastal populations persist, but there is no genetic or morphological evidence (Domning and Hayek 1986, Vianna et al. 2006, Keith Diagne 2014).|
|Red List Category & Criteria:||Vulnerable A3cd; C1 ver 3.1|
|Assessor(s):||Keith Diagne, L.|
|Contributor(s):||Powell, J. & Kouadio, A.|
This species is data limited with little new quantitative information since the previous assessment. Inference of a single generation time of up to 30 years in an unexploited population is based on data from the assessment for T. manatus latirostris. The level of threats, particularly hunting and incidental catches, appears to be continuing to increase throughout range with locally high rates and near extirpation in some regions. Lack of protein and continued poverty for human populations, and limited enforcement of national laws, are expected to drive increasing illegal hunting levels. Destruction of coastal areas due to development, mangrove harvesting, siltation and dams are resulting in reduced habitat. We infer a high probability that a 30% or greater reduction in population size will result within a 90 year three generation period (Vulnerable A3cd).
Using survey information from Côte d'Ivoire, Gabon, Guinea-Bissau, The Gambia, Senegal and Cameroon, and inferring what is known about Manatee habitat in other range states and Manatee density data for T. manatus, it is estimated that there are fewer than 10,000 Manatees in Africa. A continuing population decline of at least 10% in a 90 year three generation period, is anticipated based on continuing and increasing anthropogenic threats (Vulnerable C1).
The African Manatee therefore qualifies for listing as Vulnerable.
|Previously published Red List assessments:||
Trichechus senegalensis occurs in Angola, Benin, Cameroon, Chad, Republic of the Congo, 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. This species occurs in most of the coastal marine waters, brackish estuaries, and adjacent rivers along the coast of western Africa from southern Mauritania (16°N) to the Cuanza and Longa Rivers, Angola (9°S) (Beal 1939, Allen 1942, Blancou 1960, Robinson 1971, Husar 1978, Nishiwaki 1984, Grigione 1996, Powell 1996, Perrin 2001, Dodman et al. 2008). They ascend most major rivers within their range until cataracts, dams or shallow water prevents their progress. In some rivers, such as along the Benue and Oueme Rivers, Manatees seek refuge during the dry season in permanent lakes that communicate with the rivers during high water but are cutoff when river waters subside (Sykes 1974, Chabi-Yaouré 2012). Manatees can be found 110 km offshore among the shallow coastal flats and mangrove creeks (with abundant seagrasses and calm water) of the Bijagos Archipelago of Guinea-Bissau (Powell 1990) as well as offshore of Delta Saloum, Senegal. In recent times, hydroelectric and agricultural dams have also isolated Manatee populations in many major rivers (see Threats Section). Manatees are found in the upper reaches of Niger River in the inland delta of Mali and as far as Koulikoro, which are the furthest inland records, over 2,000 km from the ocean (Kienta 1982, Timbo 2010, Berthe 2011, Keith Diagne 2014). They occur along the entire length of the Gambia River, penetrating into Senegal where there are records as far upstream as Niokola-Koba National Park (Hill et al. 1998, P. Brillant pers. comm.). There are also reports of Manatees further upstream in the Gambia River in Guinea (Dodman et al. 2008). In Chad, Manatees are present in Lake Léré and Lake Tréné and in the Mayo-Kebbi river (Hatt 1934, Salkind 1998). Manatees are believed to have been extirpated from Lake Chad by 1929 and no longer occur in the Chad Basin (Salkind 1998). Centres of population appear to be Guinea-Bissau, the lakes and coastal lagoons of Gabon, the lagoons of Ivory Coast, the Niger River in Mali and Nigeria, Sanaga River and coastal Cameroon, and the lower reaches of the Congo River (Powell 1996, Silva and Araújo 2001, Keith et al. 2006, Keith and Collins 2007, Keith Diagne 2011, Takoukam 2012). The Manatee population in Africa is reported to be reduced, but their present range appears to be comparable to historic reports (Husar 1978, Dodman et al. 2008).
Occurrence in major rivers from north to south including lakes within these river systems: the Senegal, Saloum, Gambia, Casamance, Cacheu, Mansoa, Geba, Grande de Bulba, Tombali, Cacine, Kogon, Kondoure, Sierra Leone, Great Scarcies, Little Scarcies, Sherbro, Malem, Waanje, Sewa, Missunado, Cavally, St. Paul, Morro, St. John, Bandama, Niouniourou, Sassandra, Comoe, Bia, Tano, Volta, Mono, Oueme, Niger, Mekrou, Benue, Cross, Pie, Katsena Ala, Deb, Okigb, Issa, Bani, Akwayafe, del Rey, Ngosso, Andokat, Mene, Munaya, Wouri, Sanaga, Faro, Chari, Bamaingui, Bahr-Kieta, Logoné, Mitémélé, Gabon, Ogooué, Nyanga, Lovanzi, Kouilou, Loémé, Congo, Loge, Dande, Bengo, Cuanza, and Longa.
Occurrence in major lakes: Lake Guiers (Senegal); Lake Volta (Ghana); Inland Niger delta (Mali); Lake Léré and Lake de Tréné (Chad); Lake Togo (Togo); Lake Aheme (Benin); Lake Onangue, Lake Ezanga, Lake Mandje (Cachimba) (Gabon).
Occurrence in major lagoons: Digboué Lagoon, Tadia Lagoon, Ebrié Lagoon, Fresco Lagoon, Bandama Lagoon, Comoe Lagoon, (Ivory Coast); Sakumono Lagoon, Lake Songaw Lagoon, Keta Lagoon (Ghana), Grand Popo Lagoon, Lake Nokoue (Benin); Badagry Lagoon, Yewa Lagoon, Lagos Lagoon, Lekki Lagoon (Nigeria); Nkomi (Fernan Vaz) Lagoon, N’gowe (Iguela) Lagoon, N’dogo Lagoon, Banio Lagoon (Gabon); Conkouati Lagoon (Republic of the Congo); Massabi Lagoon (Cabinda).
Native:Angola (Angola); Benin; Cameroon; Chad; Congo; Congo, The Democratic Republic of the; Côte d'Ivoire; Equatorial Guinea; Gabon; Gambia; Ghana; Guinea; Guinea-Bissau; Liberia; Mali; Mauritania; Niger; Nigeria; Senegal; Sierra Leone; Togo
|FAO Marine Fishing Areas:||
Atlantic – southeast; Atlantic – eastern central
|Upper elevation limit (metres):||5|
|Lower depth limit (metres):||5|
|Range Map:||Click here to open the map viewer and explore range.|
There are no population estimates based on quantitative information. Nishiwaki et al. (1982) and Nishiwaki (1984) made a number of intuitive estimates for 15 countries, based primarily on interviews rather than direct surveys. Roth and Waitkuwait (1986) and Akoi (2004) made estimates of 750-800 Manatees for Côte d'Ivoire. In 1999 a report by ABE estimated the Manatee population in Benin at 125 individuals. There are no population number estimates for other countries at this time. The first genetics analyses for the species indicated high haplotype diversity and strong population structure but included samples from few individuals (Parr 2000, Parr and Duffield 2002, Vianna et al. 2006). More recent mitochondrial DNA analyses using 63 new samples from eight countries identified sixteen new control region and nine new cytochrome-b haplotypes for the species (Keith Diagne 2014). These are the first African Manatee genetic results from Senegal, Guinea, Mali, Ivory Coast and Benin. New haplotypes were characterized by high haplotype diversity, but low nucleotide diversity, indicating expansion after a period of low effective population size (Keith Diagne 2014). Phylogenetic trees identified two clades aligned geographically, indicating regional population separation likely due to low recent dispersal (Keith Diagne 2014). Ongoing mitochondrial and nuclear genetics analyses will probably allow for population estimates for Gabon and Senegal in the near future (Keith Diagne unpublished data). The Lake Chad population has probably been extirpated. It was reported that Manatees were gone from Lake Chad by 1929 (Hatt 1934, Salkind 1998), and although reports of them occurred in the Chari, Bamingui, Bahr-Kieta, and Logone Rivers leading into Lake Chad, Salkind (1998) reported that they were gone from these waterways as well. Today the drying and desertification of Lake Chad no longer provides much suitable habitat.
|Current Population Trend:||Unknown|
|Habitat and Ecology:||
West and Central Africa contain a variety of suitable habitats for Manatees ranging from large and small rivers, coastal estuaries, freshwater and saltwater lagoons, shallow quiet coastal bays, lakes and reservoirs. Like T. manatus, T. senegalensis inhabits practically every accessible habitat (Powell 1996, Dodman et al. 2008). They have been observed or recorded from coastal areas, estuarine lagoons, large rivers that range from brackish to fresh water, freshwater lakes and the extreme upper reaches of rivers above cataracts. In general, their habitat requirements seem to be similar to T. manatus and require sheltered water with access to food and freshwater (Reep and Bonde 2006, Marsh et al. 2012). They may transit areas of unsheltered coast, but they are usually rare in these areas.
|Continuing decline in area, extent and/or quality of habitat:||Yes|
|Generation Length (years):||30|
|Movement patterns:||Full Migrant|
|Use and Trade:||Manatees are exploited for their meat nearly everywhere they are found, and in many countries the rest of the carcass is discarded. However, in certain countries such as Nigeria, Togo, and Côte d’Ivoire they are also hunted for their skin, bones and oil for traditional medicines and rituals (see details under Threats). Live animals are also occasionally caught and exported to aquaria (see details under Population and Threats).|
T. senegalensis population decline has been largely attributed to hunting and incidental capture in fishing nets (Allen 1942, Cadenat 1957, Blancou 1960, Dodman et al. 2008). Although hunting is now illegal in every country in which the African Manatee occurs, laws are often not enforced and hunting and incidental captures are still not being accurately documented in most countries. Manatees are exploited for their meat nearly everywhere they are found, and in many countries the rest of the carcass is discarded. However, in certain countries such as Nigeria, Togo, and Côte d’Ivoire they are also hunted for their skin, bones, and oil for traditional medicines and rituals. They are hunted by various methods including nets, weirs, large box traps, drop traps using harpoons and snag lines, and hand-thrown harpoons (Kombo and Toko 1991, Powell 1996, Reeves et al. 1988, Roth and Waitkuwait 1986, Akoi 1992, Collins et al. 2011). The African Manatee is at the greatest risk of extinction due to the high levels of human poverty within its range of distribution (Marsh et al. 2012).
In Côte d’Ivoire, Powell (1996) sighted Manatees on a daily basis, but found numerous large box traps situated around the rivers and lagoons from the Ghana border to Fresco. The 4 x 1 m traps are constructed of wooden poles stuck in the bottom and a door weighted with a large rock. Powell (1996) built two of these box traps for catching Manatees to radio tag; he caught five Manatees in two traps over four days. These traps are also used in Nigeria and Ghana (B. Dunsin unpublished data, M. Yelibora pers. comm.). Manatees are also caught in special nets with large mesh used specifically for Manatees. In Guinea-Bissau, Silva and Araújo (2001) reported 209 deaths from 1990–1998; of these, 72% died in fishing gear, 13% were hunted, 4% stranded at low tide and 11% the cause of death was undetermined.
Incidental bycatch in fishing gear is also a major threat in all African countries, and even when captured alive, most incidentally caught Manatees are not released, but are killed. Takoukam et al. (2012) reported 13 Manatees incidentally caught and killed in fishing gear in nine months in coastal Cameroon. Cadenat (1957) recorded the deaths of five Manatees around Joal, Senegal in nets used for catching sharks. Manatees are frequently caught in monofilament nets that are now commonly used in all African countries. Manatees are occasionally killed in fishing trawls. In Côte d’Ivoire, stationary funnel nets are placed across the inlets of major rivers to catch shrimp swept past on tidal currents. These are strong nets that have a wide mouth that faces upstream and then narrows down to a small bag on the cod end. The tidal currents where they are usually set are often strong and several of these nets can block the entire channel. Between 1986 and 1988, three Manatees were killed in the vicinity of Grand Lahou by drowning in these nets, including one radio tagged Manatee (Powell 1996). Akoi (1992) described how Manatees in Côte d’Ivoire are sometimes caught in fishing weirs made of sticks. These weirs are common in Côte d’Ivoire and in many other areas in Africa.
In some locales there have also been reports of killings of large numbers of Manatees over a short period of time, such as 17 individuals killed in the Afram Arm of Lake Volta (Ofori-Danson and Agbogah 1995), 77 Manatees in the Cuanza River Angola in 1998 (Morais 2006), and 133 Manatees killed over three years in the Abanga River in Gabon (Louembet 2008). Johnson (1937) reported that as many as 12 Manatees a day were caught in a 100 mile (161 km) stretch of the Gambia River. Powell (1985) estimated around two Manatees a year were taken between 1978-1983 from this same area though this change cannot be attributed to less hunting pressure or reduced Manatee numbers (or both). If these large scale hunting operations are not curbed, it is entirely possible that the species will become extinct in certain places.
Due to poverty, remoteness and lack of enforcement, Manatees are taken for food and traditional medicinal products throughout their range (Powell 1996). Manatee meat is openly sold in local markets. In Cameroon, Manatee meat was sold along the roadside near Douala and could easily be spotted from a passing car. Manatee meat was seen on three out of five visits during a three month period (J. Powell pers. obs.). In the market in Lambarene, Gabon, Manatee meat was documented nine times between March 2012 and March 2013, as well as additional reports of Manatee being served in local restaurants during the same time period (Mvele and Arrowood 2013a). Manatee meat and oil is reported to move illegally in trade from Chad to Nigeria and Cameroon (Powell 1996, A. Wachoum pers. comm.). In Mali, Nigeria, and Chad, Manatee oil is more prized than the meat. The oil is used for its reputed medicinal properties to cure rheumatism and to condition the skin and hair (Kienta 1982, Reeves et al. 1988). Oil from the head is used to treat ear infections. In Mali and along the Benue River, certain cuts of the meat are considered to have particular useful properties. For example, the parts of the penis are used to cure impotency in men, and the skin can be made into whips (Kienta 1982, Powell 1996). In Sierra Leone, villagers consume all parts of the Manatee carcass except for the heavy ribs (Reeves et al. 1988). The meat is shared among villagers and any remains are sold by the trapper. The bones are used to make handles for walking sticks or spinning-tops used in a local game called cii. Little historical data exists for comparison to the present to know if decreases in catch rates are occurring over time.
Recent threats include loss of habitat due to damming of rivers, cutting of mangroves for firewood and destruction of wetlands for agricultural development. Coastal development all along the western side of the African continent is decreasing Manatee habitat.
In recent times hydroelectric and agricultural dams have also isolated Manatee populations in many major rivers, including in Lake Volta, Ghana (Akosombo Dam, constructed in 1965), the Niger River (Kainji Dam in Nigeria, constructed in 1968, and the Markala Dam in Mali, completed in 1945), and the Senegal River (Diama Dam, constructed in 1983 and the Kayes Dam in Mali). Since 2008, the Niger River Basin Authority has authorized the construction of three additional multi-purpose dams: at Fomi in Guinea, Taoussa in Mali, and Kandjadji in Niger (Diarra 2011). An additional dam has also been authorized at Kayes Mali on the Senegal River. All of these are likely to further restrict Manatee habitat in these countries and lead to genetic isolation of populations. At the Kanji dam on the Niger River, Nigeria and at the Akosombo dam on the Volta River, Ghana, Manatees have been known to be killed in the turbines and intake of the hydro-electric generator (Powell 1996). In Nigeria, for example, Isahaya (pers. comm.) reported seeing as many as six Manatee carcasses at one time below the Kainji dam. An agricultural dam constructed in 2008 at Navel, Senegal on a seasonal tributary of the Senegal River killed five Manatees within the first four years after it was built: three due to drowning against dam grates and two due to entrapment behind the dam. Seven other live Manatees were rescued from behind the same dam and released back into the Senegal River (Oceanium Dakar and L. Keith Diagne unpublished data).
In countries including Benin, Senegal, and Angola, Manatees can become trapped in small lakes as rivers and flooded areas dry up in the dry season (Dossou-Bodjrènou et al. 2006, Morais 2006, Oceanium Dakar unpublished data). In some cases, such as during a severe drought in Lake Guiers in the 1970s, Manatees died due to stranding (Dupuy and Maigret 1978). In other cases, becoming trapped in these smaller bodies of water makes Manatees more vulnerable to hunting.
Coastal development near Abidjan, Côte d’Ivoire resulted in loss of habitat and increased human disturbance contributing to the disappearance of Manatees in the area. Although still rare in Africa, increases in motorized boats and large vessel traffic in some of the rivers and lagoons may also pose a threat from collisions with watercraft, the highest known cause of death in Florida and Belizean Manatee populations. A pregnant female Manatee was struck and killed by a boat at a natural gas port at the mouth of the Congo River in Angola in 2007, and residents of nearby villages report a large decrease in Manatee sightings in the area since construction on the large facility began (L. Keith Diagne unpublished data).
National and international trade in live Manatees exists. In Nigeria and Mali Manatees have been captured for exhibit in local zoos. These Manatees usually die after a short time in captivity because their caretakers have not been properly trained and/or did not provide them enough food. Between 2000 – 2010, CITES records show that a total of 28 live Manatees were exported from four African countries (Cameroon, Guinea, Guinea-Bissau, and Côte d’Ivoire) to aquaria in Asia (Japan, Korea, China, and Taiwan). Wild caught Manatees from Guinea-Bissau are offered for sale on the internet (River Zoo Farms). However, with the up-listing of the species to CITES Appendix I in March 2013, international trade is no longer legal.
The African Manatee is one of the least understood marine mammals in the world, and has recently been shown to be the least studied large mammal in Africa (Trimble and Van Aarde 2010). They are often referred to as the "forgotten" sirenian. African Manatees were up-listed from CITES Appendix II to Appendix I as of the Conference of Parties 16 in March 2013. They are also listed on Appendix I of the Convention on Migratory Species and are protected by national laws in all range states. In 2013 the IUCN SSC Sirenian Specialist Group created an African Manatee Subgroup in order to focus conservation efforts for the species. Though African Manatees are protected throughout their range, enforcement and control of hunting appears negligible. Hunting is largely local and sometimes ritualized and the meat is usually consumed locally. In some regions, hunting is primarily opportunistic and meat and products are traded locally and across borders. Awareness of the protected status of the Manatee is widespread in most areas surveyed, but often there is little perceived fear of arrest and punishment (Powell 1996); enforcement is rare and fines or sentences for the most part have been negligible. Frequently when individuals have been arrested, the fine can be less than what is gained by selling the Manatee meat and oil in the market (Powell 1996). Although in general protection is minimal and offtake is probably at unsustainable levels, progress has been made in some regions to discourage hunting. Oboto (2002) mentions that in some parts of Nigeria people are afraid to hunt Manatees for fear of arrest. In Senegal the Ministries of Water and Forestry and National Parks have been very proactive in participating in Manatee rescue and research activities along the Senegal River and Lake Guiers, so people are aware that they will be arrested if they hunt Manatees, and as a result there has been almost no hunting in these places for at least the last five years (L. Keith Diagne unpublished data). In an effort to encourage law enforcement agencies to arrest hunters, the Species Survival Network is creating informational posters that will be distributed to wildlife law enforcement agencies in all African Manatee range countries. It is important for Manatee researchers to work together with wildlife law enforcement and to provide data to assist the enforcement of Manatee protection laws, but to date these relationships are limited to only a couple African countries.
The species is believed to be in decline throughout much of its range, but without accurate baseline information it is impossible to know how to conserve these Manatees, and conservation is also unlikely without capacity building. A lack of long-term, committed funding, as well as the difficulty of accessing the extremely remote regions where African Manatees live, murky water habitat throughout their range, and the animals’ elusiveness, have severely limited studies. This species is only likely to be conserved through a network of grassroots, localized efforts by African researchers dedicated to long-term conservation and education efforts in their countries, and through increased funding to conservation activities.
Côte d’Ivoire had one of the most important Manatee conservation programs from 1989–2009 (Akoi 1992, Akoi 1994, Akoi 2000, Akoi 2004) but unfortunately it ended with the death of its leader, K. Akoi. Akoi’s staff were left with no support when funding was withdrawn after his death. This was a hard lesson that too often Manatee programs in Africa are dependent on the work of individuals. More people need to be trained and efforts need to be integrated into broader conservation programs so that Manatee conservation initiatives do not end if one person is no longer able to continue the work.
Many new African Manatee conservation initiatives have begun since 2008. From 2007–2009 the Earthwatch Institute (UK) funded annual training workshops for African biologists interested to begin Manatee research and conservation activities. The workshops were held at Lake Volta, Ghana and were led by P. Ofori-Danson, C. Self-Sullivan, and L. Keith Diagne. Over three years 33 participants from 17 African countries were trained, and equally importantly, a spirit of collaboration was born. When Earthwatch funding ended, L. Keith Diagne continued the training workshops in other countries, and built an African Manatee researcher network to increase and sustain communication between researchers in different countries, increase data collection, conservation activities, and educational awareness programs. The long-term strategy is to create a sustainable and cohesive network of African researchers who will determine population sizes and status of African Manatees in a majority of the 21 range countries, as well as develop and implement management plans for conservation of the species. The network continues to try to identify collaborators from all 21 countries. As of 2015, L. Keith Diagne has conducted five additional training workshops in Gabon, Mali, The Gambia, and Guinea-Bissau for 80 African biologists from 19 countries. In May 2010, Wetlands International Africa (WIA) conducted a training workshop in Senegal with a modular course given by P. Ofori-Danson to 17 local experts and wildlife managers from six African countries. General recommendations for this initiative were presented afterwards (Morales-Vela and Castelblanco-Martinez 2011). In 2013 and 2014, A. Kamla Takoukam also conducted two training workshops in Cameroon for 30 biologists. Year-round Manatee research now occurs in nine countries.
Current African Manatee research and conservation projects include:
List of protected areas in western Africa where Trichechus senegalensis is known to occur:
|Citation:||Keith Diagne, L. 2015. Trichechus senegalensis. The IUCN Red List of Threatened Species 2015: e.T22104A81904980. . Downloaded on 24 May 2016.|