Manatees are large, fully aquatic, herbivorous marine mammals often called “sea cows” due to their grazing habits. They belong to the order Sirenia, a group of mammals that also includes the dugong. Known for their gentle nature and slow movements, manatees inhabit shallow, marshy coastal areas and river systems globally. Clarifying the specific number of scientifically recognized species is necessary to understand these distinct populations.
The Three Recognized Living Species
The manatee family, Trichechidae, currently contains three accepted species within the genus Trichechus. These species are distinguished primarily by geographic isolation and habitat specialization. The largest and most widely known is the West Indian Manatee (Trichechus manatus), which is distributed across the Caribbean, Gulf of Mexico, and Atlantic coasts of the Americas.
The second species is the West African Manatee (Trichechus senegalensis), found in shallow coastal waters, estuaries, and river systems along the western edge of Africa. The Amazonian Manatee (Trichechus inunguis) is the only species that lives exclusively in freshwater environments. This species is endemic to the Amazon River basin and its tributaries, never venturing into brackish or marine habitats.
The Amazonian manatee is also physically distinct, lacking the nails on its flippers that are present on the other two species. While the West Indian and West African manatees utilize a mix of marine, brackish, and freshwater locations, the Amazonian species is entirely reliant on the South American river system for its survival. Identifying these three species provides the definitive count of living manatees.
Geographic Range and Subspecies Classification
The global distribution of manatees spans three continents: North America, South America, and Africa. The West Indian Manatee (Trichechus manatus) covers the largest range and is categorized into two subspecies based on genetic and morphological differences. This classification recognizes distinct populations within the broader species.
The Florida Manatee (T. m. latirostris) is the northern subspecies, primarily occupying the southeastern United States, including the Florida peninsula and the Gulf Coast. The Antillean Manatee (T. m. manatus) ranges throughout the Caribbean islands, Central America, and the northern coast of South America. These two groups are reproductively isolated by geography, justifying their separate subspecies designation.
The West African Manatee is found along the coast from Senegal to Angola, often moving far up large rivers like the Niger. The Amazonian Manatee is confined to the expansive, warm freshwater networks of the Amazon basin, including parts of Brazil, Peru, and Colombia. This geographic separation, including the division of the West Indian species into two subspecies, highlights the localized nature of manatee populations.
Steller’s Sea Cow and the Sirenian Order
Discussions about manatee species often involve the broader order Sirenia, which contains four living species: the three manatees and the dugong. This group once included the enormous Steller’s Sea Cow (Hydrodamalis gigas), which is sometimes mistakenly counted among manatee species. Steller’s Sea Cow was an extinct sirenian that was dramatically larger than any manatee, reaching lengths of up to 10 meters.
Steller’s Sea Cow belonged to the family Dugongidae, making it a closer relative of the dugong than of the manatees (family Trichechidae). The animal was discovered in 1741 near the Commander Islands in the Bering Sea but was hunted to extinction within just 27 years. Its existence in the cold North Pacific contrasted sharply with the tropical and subtropical habitats of all living manatees and dugongs. Clarifying its classification as a separate, extinct member of the Sirenian order ensures accuracy.
Global Conservation Status and Threats
All three manatee species are currently listed as vulnerable to extinction on the IUCN Red List of Threatened Species. This status reflects the ongoing pressures facing these slow-moving animals across their habitats. The two subspecies of the West Indian Manatee, the Florida and Antillean populations, face an even higher risk, as both are listed as Endangered at the subspecies level under IUCN criteria.
One significant human-related threat is collision with watercraft, commonly known as boat strikes, which frequently injure or kill manatees in coastal areas. Habitat loss poses a serious problem, particularly the destruction of warm-water refuges required for cold weather survival. In Florida, pollution-fueled loss of seagrass, their primary food source, has led to a recent Unusual Mortality Event.
Additional threats include entanglement in fishing gear and exposure to harmful algal blooms, such as red tide, which can be toxic when ingested. The West African Manatee also contends with hunting pressure and habitat disruption from dam construction on its rivers. Conservation efforts focus on regulating boat speeds, protecting warm-water sites, and mitigating pollution to preserve these vulnerable aquatic mammals.