Animal Diversity Web

Geographic Range

Trichechus senegalensis occurs along the west coast of Africa. The Senegal River marks the northern limit of their range while the Cuanza River of Angola serves as the southern boundary.

• Biogeographic Regions
• ethiopian
  • native
• atlantic ocean
  • native

Habitat

Trichechus senegalensis are found in shallow coastal wasters and freshwater rivers. They appear to prefer large, shallow estuaries and weedy swamps, and have been reported to avoid salt water (Nowak 1991 and Nishiwaki 1984). Their range is limited by temperature. They are rarely found in waters of less than 18 degrees celsius (Nowak 1991).

• Habitat Regions
• tropical
• saltwater or marine
• freshwater

• Aquatic Biomes
• rivers and streams
• coastal
• brackish water

• Other Habitat Features
• estuarine

Physical Description

• Other Physical Features
• endothermic
• bilateral symmetry

Reproduction

Trichechus senegalensis is a poorly studied species, and much of the information about their behavior and reproduction has been inferred based on their close similarity to the very well studied Trichechus manatus. They are capable of reproducing throughout the year; however, a peak in calving tends to occur in late spring or early summer (CMC 1997). Females are sexually mature as early as three years of age. A female in estrus is joined by a dozen or more males. Together they form a mating group in which copulation appears to occur at random (Save the Manatee Club 1997). Gestation lasts about 13 months and usually a single calf is born at a time, but twins do occur occasionally. Calves are born tail first, and they can swim on their own (CMC 1997). They feed from a pair of pectoral mammary glands. Trichechus senegalensis are believed to live to about 30 years of age, and females can bear young every three to five years (Sikes 1974 and CMC 1997).

• Key Reproductive Features
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual

Behavior

Again, the behavior of this species is poorly studied. They are believed to be at least partially nocturnal, as this is when most hunters successfully take manatees (Sikes 1974). Trichechus senegalensis may live singly or in family groups of up to four to six individuals (Nowak 1991). They have few natural predators, and perhaps as a result they do not have a very sophisticated social system. The strongest bond between individuals occurs between a mother and her calf. Calves may remain dependent on their mothers for up to two years (Save the Manatee Club 1997).

• Key Behaviors
• motile

Communication and Perception

• Perception Channels
• tactile
• chemical

Food Habits

Trichechus senegalensis feeds primarily on aquatic vegetation, and adults may consume up to 8000kg per year. They may also feed on overhanging bank growth, and populations living in estuarine environments are reported to feed exclusively on mangroves (Nowak 1991). In many areas, local fishermen claim that Trichechus senegalensis are responsible for stealing fish from nets. However, this behavior has yet to be confirmed (Reeves et. al. 1988). Trichechus senegalensis are dependent upon microorganisms living in their large intestines to aid in the digestion of certain plant materials (Rathbun 1990).

Economic Importance for Humans: Positive

Villagers in Sierra Leone and Nigeria hunt Trichechus senegalensis for their meat (Reeves et. al. 1988). They have developed elaborate means of trapping the animals which they eventually kill with harpoons or guns (Sikes 1974 and Robinson 1971). In contrast to this, villagers in Cameroon have a different perception of Trichechus senegalensis. They do not like the taste of the meat and they believe that Trichechus senegalensis are fierce animals that become violent when attacked. Nigerian fishermen are often responsible for the poaching of Trichechus senegalensis in Cameroon (Grigione 1996). It has also been reported that the skin of Trichechus senegalensis has medicinal and therapeutic properties (Reeeves et. al. 1988).

Economic Importance for Humans: Negative

Villagers in Sierra Leone consider Trichechus senegalensis a major pest of rice crops. Fishermen believe these animals are responsible for removing fish from nets, but this is unconfirmed (Reeves et. al. 1988).

Conservation Status

• IUCN Red List

  Vulnerable
  More information

Other Comments

Trichechus senegalensis are the source of many myths and legends. They have often been mistaken for mermaids. The blubber is believed to have curative powers and possession of body parts, especially the skull and teeth, is believed to confer special status in many aspects of life, including sports, politics, and academics (Sikes 1974).

They are known in West Africa as "dikunge" and "peixe-muhler".

Contributors

Ethan Kane (author), University of Michigan-Ann Arbor.

References

Center for Marine Conservation. 1997. Manatees and Dugongs. http:// www.cmc-ocean.org./22231m2_manatee.html

Grigione, M. M. 1996. Observations on the Status and Distribution of the West African Manatee in Cameroon. African Journal of Ecology, 34:189-195.

Nishiwaki, M. 1984. Current Status of the African Manatee. Acta Zoologica Fennica, 172:135-136.

Nowak, R. M. 1991. Walker's Mammals of the World. Fifth Edition. Johns Hopkins University Press, Baltimore.

Rathbun, G. B. 1990. Manatees. Grzimek's Encyclopedia of Mammals. McGraw-Hill, New York.

Reeves, R. R., D. Tuboku-Metzger, and R. A. Kapindi. 1988. Distribution and Exploitation of Manatees in Sierra Leone. Oryx, 22:75-84.

Robinson, P. T. 1971. Wildlife Trends in Liberia and Sierra Leone. Oryx, 11:117-122.

Save the Manatee Club. 1997. Membership Handbook. Maitland, Florida.

Sikes, S. 1974. How to Save the Mermaids. Oryx, 12:465-470.