Manatee Facts

An adult West Indian manatee runs 8 to 13 feet and 440 to 1,300 pounds, some females over 3,000, on a streamlined body ending in a broad, flattened paddle tail that drives it with slow, undulating strokes. Its forelimbs are flexible flippers tipped with three or four vestigial toenails — a nod to its land ancestors — used to steer, crawl the riverbed, and hold vegetation. Manatees belong to the order Sirenia (family Trichechidae); despite looking seal- or whale-like they are not related to those groups but, by convergent evolution, are closest to elephants and hyraxes. Dense, marrow-free bones act as ballast against the buoyancy of their large lungs and gut, their whole body is sparsely covered in tactile hairs (vibrissae) that read water movement where visibility is poor, and a muscular, split upper lip grips and gathers plants.

The West Indian manatee ranges through the warm western Atlantic, Caribbean, and Gulf of Mexico, from the southeastern U.S. — chiefly Florida — through the Greater Antilles, eastern Mexico, and Central America to Brazil. It moves freely between marine, brackish, and freshwater — shallow coasts, mangrove estuaries, slow rivers, and quiet bays — but temperature sets the limit. With a very low metabolic rate and no insulating blubber, manatees suffer cold stress below about 68°F, so in winter Florida animals crowd into warm-water refuges around natural springs and the thermal outflows of power plants.

As one of the ocean's only strictly herbivorous mammals (with the dugong), a manatee grazes up to eight hours a day, eating 10 to 15% of its body weight — 100 to 150 pounds of wet vegetation — daily across more than 60 plant species, favouring manatee grass, turtle grass, shoal grass, water hyacinth, and red mangrove leaves. Its bristly, prehensile lips strip plants from the bottom. Because that diet is so abrasive with silica and sand, it grows "marching molars": lacking incisors and canines, it has only identical molars that wear down, drop out at the front, and are replaced by new ones erupting at the back and migrating forward through life. A huge hindgut ferments the cellulose over 5 to 7 days.

Manatees are largely solitary or loosely social, with no territories or hierarchy; they may gather in the hundreds at winter warm-water sites or rich feeding grounds, but those groupings are temporary, and the only lasting bond is between a cow and her calf. They are extremely docile, spending most of their time eating, traveling, and resting — a resting manatee sinks and rises automatically to breathe every 3 to 5 minutes while asleep — and keep contact through chirps, squeaks, and grunts, vital between cow and calf in cloudy water. Cruising at 3 to 5 mph, they can still burst to 15 mph if startled.

Manatee reproduction is slow and high-investment. Females mature at 3 to 5 years, and a female in estrus draws a "mating herd" of a dozen or more bulls that pursue her for weeks. Gestation is a long 12 to 14 months, and the cow bears a single 60-to-70-pound calf underwater (twins are very rare); it can reach the surface for its first breath at once and nurses from mammary glands behind the front flippers. The calf stays with its mother up to two years, learning warm-water refuges, migration routes, and feeding grounds. Manatees that survive the early years often live 40 to 60 years.

The West Indian manatee is Vulnerable, downlisted from Endangered after slow population gains in places like Florida, but still heavily imperiled by human activity; it has essentially no natural predators, though sharks or crocodiles may rarely take a calf. The foremost threat is collision with boats — slow and needing to surface, manatees are struck by hulls and propellers, and most adults can be identified by the unique white propeller scars on their backs. Habitat degradation is the looming crisis: nutrient pollution from farm runoff and failing septic systems fuels persistent harmful algal blooms that block sunlight and kill the seagrass beds manatees depend on, causing localized starvation. Protecting coastal habitat, enforcing slow-speed zones, and restoring water quality are essential to the sea cow's future.

• Save the Manatee Club: Manatee Facts and Information
• Florida Fish and Wildlife Conservation Commission (FWC): Manatee Program
• IUCN Red List of Threatened Species: Trichechus manatus
• U.S. Fish and Wildlife Service: West Indian Manatee Profile