West Indian Manatee

The average West Indian manatee is about 2.7–3.5 m (8.9–11.5 ft) long and weighs 200–600 kg (440–1,320 lb), with females generally larger than males. The largest individual on record weighed 1,655 kg (3,649 lb) and measured 4.6 m (15 ft) long. Manatees are estimated to live 50 years or more in the wild, and one captive Florida manatee, Snooty, lived for 69 years (1948–2017). A captive manatee named Romeo, held at the Gulfarium Marine Adventure Park in Fort Walton Beach, was recognized as the world record holder at 71 years of age in February 2026.

The West Indian manatee inhabits mostly shallow coastal areas, including rivers and estuaries. Manatees can withstand large changes in salinity and are found in both freshwater and saltwater. Manatees' extremely low metabolic rate and lack of a thick layer of insulating body fat limits them to locations with warm waters, including tropical regions.

Because manatees evolved in habitats without natural predators, they lack predator avoidance behavior. The large size and low metabolic rates of manatees lends to their capacity for long and deep dives, as well as their relative lack of speed. Manatees are frequently solitary creatures, but they do aggregate at warm-water habitats during the winter and during the formation of breeding herds. In spite of their docile demeanor, due to their large size the West Indian manatee has nearly no natural predators in its native environment. American alligators and American crocodiles have been suspected to on occasion take a manatee. A dying manatee was discovered in Puerto Rico, wounded by a large shark bite thought to be inflicted by either a tiger shark or bull shark.

Male manatees reach sexual maturity at 3–4 years of age, while females reach sexual maturity at 3–5 years of age. Manatees appear capable of breeding throughout their entire adult life, although most females first breed successfully at ages 7–9. Breeding occurs in ephemeral mating herds, where several males aggregate around an estrous female and compete for access to her. These mating herds can last up to 2 to 4 weeks. The estrous cycles of female manatees typically are approximately one month long. Females in captivity have been observed to skip cycles. Larger males, presumably older, have been observed to dominate mating herds and are likely responsible for most successful copulation events. However, between males and females there is a little sexual dimorphism where females are typically slightly larger than males.

The West Indian manatee has been included on the U.S. Endangered Species List since the 1970s. Late in 2023, the International Union for Conservation of Nature (IUCN) assessed the West Indian manatee and the Florida subspecies as vulnerable, and the Antillean subspecies as endangered. The full species and both subspecies qualified for their respective classifications due to a combination of a low number of mature individuals, and a significant projected decline in total population numbers over the next two generations (about 20 years per generation in manatees). Similarly, NatureServe considers both the Florida subspecies and the species as a whole as imperiled.