Manatees originated in Africa roughly 60 million years ago, making them one of the oldest lineages of mammals to transition from land to water. They beat whales to the ocean by about 30 million years and seals by about 10 million. Today, three species of manatee live across the tropical and subtropical waters of the Americas and West Africa, but their story starts on land, with ancestors that walked on four legs and share a surprising family tree with elephants.
Ancient Land Animals That Took to the Water
Manatees belong to an order of marine mammals called Sirenia, which first appeared in Africa around 60 million years ago during the early Cenozoic, the era that followed the extinction of the dinosaurs. At that time, Africa was isolated from other continents, and a unique group of mammals called afrotherians evolved there in relative isolation. Manatees are part of this group, and their closest living relatives are elephants. The two lineages split apart roughly 60 to 80 million years ago, and the earliest fossil ancestors of both groups come from northern Africa.
The oldest known fossil sea cows had four limbs and could walk on land. Over millions of years, their bodies reshaped for life in the water: hind limbs disappeared, front limbs flattened into flippers, and their bones became unusually thick and dense. That bone density acts like a built-in weight belt, helping manatees stay submerged and hover near the bottom where they feed. By about 12 million years ago, during the middle Miocene, the ancestors of modern manatees and their close relative the dugong had already settled into the distinct tropical habitats they occupy today.
Three Living Species and Where They Live
There are three species of manatee alive today, each occupying a different part of the world. They share a common ancestor that lived roughly 31 million years ago.
West Indian Manatee
This is the most widespread species and the one most people picture. It has two subspecies: the Florida manatee and the Antillean manatee. Florida manatees live in the coastal waters, rivers, and springs of Florida, ranging west through coastal Louisiana and occasionally as far as Texas. The Antillean manatee stretches from eastern Mexico through Central America, the Caribbean islands, and down the northeastern coast of South America to Brazil. In total, the West Indian manatee is found across more than 20 countries and territories, including Guatemala, Belize, Honduras, Colombia, Venezuela, Cuba, Puerto Rico, and the Bahamas. These manatees move freely between saltwater, brackish water, and freshwater systems.
Amazonian Manatee
The Amazonian manatee is the only species that lives exclusively in freshwater. It is found throughout the Amazon River Basin in northern South America, and its movements track the seasonal flooding of the Amazon. When water levels are high, these manatees spread into flooded forests and grasslands to feed. When the water drops, some populations become confined to the deeper sections of lakes, waiting for the next flood cycle.
West African Manatee
The West African manatee lives along the coast and rivers of West Africa, making it the only manatee species found outside the Americas. It inhabits marine, brackish, and freshwater environments, much like the West Indian manatee. Its presence on both sides of the Atlantic is a living reminder that manatees trace back to the African continent.
Built for Grazing Underwater
Manatees are herbivores, often called “sea cows” because they spend hours slowly grazing on underwater vegetation. Their diet is primarily seagrasses and algae, with smaller amounts of other aquatic plants. They eat a lot: a manatee consumes somewhere between 4% and 15% of its body weight every day, spending four to eight hours feeding. For an adult weighing around 1,000 pounds, that can mean 40 to 150 pounds of vegetation daily.
The balance of their diet shifts depending on what’s available. In Florida’s Indian River Lagoon, stomach analyses from the late 1970s through the 1980s showed manatees eating mostly seagrass (about 62%) with algae making up around 28%. After major seagrass die-offs in recent years, that ratio flipped: algae became the dominant food source at nearly 50%, with seagrass dropping to about 34%. Manatees are flexible eaters, but they depend on healthy aquatic plant ecosystems to survive.
Why Warm Water Is a Survival Need
Despite their size, manatees have relatively little body fat and a slow metabolism, which makes them highly vulnerable to cold. Water temperatures below 20°C (68°F) trigger cold stress, and extended exposure at those temperatures can be fatal. When water drops below that threshold, manatees migrate to warm-water refuges, congregating in large numbers at predictable sites.
In Florida, about two-thirds of the manatee population relies on warm water discharged from power plants to survive the coldest winter days. Another 18% gather at natural warm-water springs, particularly Blue Spring on the St. Johns River and Kings Bay at the head of the Crystal River. Smaller numbers use sites like Fanning Spring, Homosassa Spring, and Chassahowitzka Spring, several of which have been dredged to improve manatee access. In 2015, the Army Corps of Engineers constructed a new thermal refuge along the Faka Union Canal in southwest Florida.
The dependence on power plant outfalls is a growing concern. As aging power plants are retired, it’s unclear whether natural springs and passive thermal basins in southern Florida can support the current population through cold snaps. Cold stress events typically produce manatee deaths starting one to two weeks after water temperatures drop below the 68°F threshold, either from a single sharp cold front or from two or more weeks of sustained cold. One documented cold event saw water temperatures averaging just 13.6°C (about 57°F) over a two-week stretch.
Where Manatees Stand Today
The West Indian manatee is listed as threatened under the U.S. Endangered Species Act. Florida’s population has rebounded significantly from its lowest points in the 20th century, but the species faces ongoing threats from boat strikes, habitat loss, and the collapse of seagrass beds that provide their primary food source. A mass starvation event in the Indian River Lagoon beginning in 2020 killed hundreds of manatees after pollution-driven algae blooms smothered the seagrass.
The Amazonian and West African species are harder to count and study, but both are considered vulnerable. The West African manatee faces threats from hunting, accidental capture in fishing nets, and dam construction that fragments river habitats. The Amazonian manatee contends with illegal hunting and the disruption of seasonal flood patterns that define its entire way of life. All three species are tied to ecosystems under pressure, and their survival depends on the health of the warm, plant-rich waters their ancestors moved into millions of years ago.