The West Indian manatee is a large, fully aquatic herbivore of the order Sirenia, found in the rivers, estuaries, and warm coastal seas of the southeastern United States, the Caribbean, Central America, and northern South America [IUCN 2024]. Often called a "sea cow," it grazes on submerged and floating vegetation and surfaces to breathe through nostrils set on the upper snout. Two subspecies are recognized: the Florida manatee (T. m. latirostris) and the Antillean, or Greater Caribbean, manatee (T. m. manatus) [IUCN 2024].
Although it has no natural predators across most of its range, the species is closely tied to human-dominated waterways, and its numbers are constrained by collisions with boats, loss of the seagrass beds it feeds on, and dependence on a limited number of warm-water sites in winter [MMC 2023; FWS 2017]. It remains at risk throughout its range.
Biology and Identification
Adult West Indian manatees typically measure about 2.7 to 3.5 meters (roughly 9 to 11.5 feet) in length and weigh between 200 and 600 kilograms (about 440 to 1,320 pounds), with females generally larger than males [USACE/FWS]. The body is robust and gray to gray-brown, tapering to a rounded, paddle-shaped tail; the forelimbs are flippers, and the upper lip is divided into prehensile pads used to manipulate plants [USACE/FWS].
Manatees are obligate herbivores, feeding on seagrass, algae, and other aquatic plants in both fresh and estuarine waters [MMC 2023]. Seagrass is a staple of the diet in coastal areas, and individuals consume large quantities of wet vegetation daily [USACE/FWS]. Because they have a low metabolic rate and little insulating body fat, manatees tolerate cold poorly; they seek warm water as temperatures fall, and prolonged exposure to water below about 18 degrees Celsius (65 degrees Fahrenheit) can be lethal [MMC 2023]. This sensitivity drives seasonal movement to warm-water sites in winter.
Habitat and Range
Trichechus manatus occupies shallow rivers, springs, estuaries, lagoons, and nearshore marine waters where aquatic vegetation is abundant [IUCN 2024]. The Florida subspecies is concentrated in the southeastern United States, while the Antillean subspecies ranges discontinuously from the Greater Antilles and the Gulf of Mexico coast of Mexico through Central America to the Atlantic coast of South America, reaching northeastern Brazil [IUCN 2024; Meirelles et al. 2022].
In the colder northern part of the range, winter distribution is governed by access to warm water. Manatees aggregate at natural warm springs such as those in the Crystal River and Blue Spring systems and at the warm-water outfalls of coastal power plants [MMC 2023]. A large share of the Florida population relies on these industrial outfalls during the coldest days, a dependence that ties the population's winter survival to infrastructure that was never designed for that purpose [MMC 2023].
Conservation Status
The West Indian manatee is assessed as Vulnerable on the IUCN Red List, under criterion C1, in the assessment published in 2024 [IUCN 2024]. The minimum number of mature individuals across the species is estimated at about 8,197, with a best estimate near 11,328, and the population is projected to decline by at least 10 percent over three generations (generation length roughly 20 years) due to habitat loss and human-caused mortality [IUCN 2024].
The two subspecies are assessed separately: the Florida manatee is treated as Vulnerable, and the Antillean (Greater Caribbean) manatee as Endangered, reflecting its smaller, more fragmented numbers and higher hunting pressure in parts of its range [IUCN 2024; Morales-Vela et al. 2024]. In the United States, the species is listed as threatened under the Endangered Species Act following a 2017 reclassification from its earlier endangered listing, a change based on the agency's analysis of population growth and habitat improvement [FWS 2017].
Threats
The leading sources of human-caused mortality differ by region. In the United States, collisions with watercraft are the primary cause of human-related manatee deaths [MMC 2023]. Loss of seagrass and other forage is an increasingly severe threat: nutrient pollution fuels algal blooms that block sunlight and kill the seagrass beds manatees depend on, and the Marine Mammal Commission has documented a sharp reduction in seagrass in affected areas since 2011 [MMC 2023].
This dynamic produced an Unusual Mortality Event along Florida's Atlantic coast that ran from December 2020 to April 2022, during which 1,255 manatee carcasses were documented, driven largely by starvation linked to widespread seagrass loss in the Indian River Lagoon; the event was formally closed in 2025 [FWC 2025]. Cold stress, harmful algal blooms (red tide), entanglement and accidental capture in fishing gear, and, in parts of the Caribbean and South America, directed hunting are additional documented threats [IUCN 2024; Meirelles et al. 2022].
What Is Being Done
In the United States, manatees are protected under the Marine Mammal Protection Act and the Endangered Species Act [MMC 2023], as well as the Florida Manatee Sanctuary Act, which underpins the designation of state sanctuary zones [FWS Crystal River]. Protected areas such as the Crystal River National Wildlife Refuge, the only national wildlife refuge established specifically for the Florida manatee, designate seasonal sanctuary zones where access is restricted during the winter months to reduce disturbance at warm-water springs [FWS Crystal River].
Managers are also working to secure the future of warm-water habitat as aging power plants are retired, including efforts to protect and restore natural springs so that manatees are less dependent on industrial outfalls [MMC 2023]. During the recent mortality event, agencies conducted a temporary supplemental-feeding program in the most affected area and expanded rescue and rehabilitation capacity [FWC 2025]. Across the Caribbean and South America, the IUCN SSC Sirenia Specialist Group coordinates population surveys, threat assessments, and national conservation planning [IUCN SSC 2025].
How You Can Help
You can support manatee conservation by learning to recognize the species and its habitat needs, and by sharing accurate, sourced information rather than alarmist claims. Observing posted speed zones and sanctuary boundaries on the water, keeping a respectful distance from animals at springs, and supporting reputable organizations and protected areas that conduct surveys, habitat restoration, and rescue work all contribute to the conservation programs described above [MMC 2023; FWS Crystal River]. Reducing nutrient runoff at the community level helps protect the seagrass beds that underpin manatee survival [MMC 2023].
References
[IUCN 2024] Deutsch, C.J. & Morales-Vela, B. (2024). Trichechus manatus (West Indian Manatee). The IUCN Red List of Threatened Species 2024: e.T22103A43792740. https://www.iucnredlist.org/species/22103/9356917
[Morales-Vela et al. 2024] Morales-Vela, B., Mignucci-Giannoni, A.A. & Quintana-Rizzo, E. (2024). Trichechus manatus ssp. manatus (Greater Caribbean Manatee). The IUCN Red List of Threatened Species 2024: e.T22105A43793924. https://dx.doi.org/10.2305/IUCN.UK.2024-2.RLTS.T22105A43793924.en
[FWS 2017] U.S. Fish and Wildlife Service. (2017). Endangered and Threatened Wildlife and Plants; Reclassification of the West Indian Manatee From Endangered to Threatened. Federal Register, 82(64), 16668. https://www.federalregister.gov/documents/2017/04/05/2017-06657/endangered-and-threatened-wildlife-and-plants-reclassification-of-the-west-indian-manatee-from
[FWS Crystal River] U.S. Fish and Wildlife Service. Crystal River National Wildlife Refuge. https://www.fws.gov/refuge/crystal-river
[MMC 2023] Marine Mammal Commission. Florida Manatee. https://www.mmc.gov/priority-topics/species-of-concern/florida-manatee/
[FWC 2025] Florida Fish and Wildlife Conservation Commission. Closed Manatee Mortality Event Along the East Coast (December 2020–April 2022). https://myfwc.com/research/manatee/rescue-mortality-response/ume/
[IUCN SSC 2025] IUCN Species Survival Commission Sirenia Specialist Group. (2025). 2024–2025 Report of the IUCN SSC Sirenia Specialist Group. https://iucn.org/sites/default/files/2025-07/2024-2025-iucn-ssc-sirenia-sg-report_publication.pdf
[USACE/FWS] U.S. Army Corps of Engineers / U.S. Fish and Wildlife Service. Biological Information on the West Indian Manatee (Trichechus manatus). https://www.saj.usace.army.mil/portals/44/docs/regulatory/sourcebook/endangered_species/manatee/manateeinfo.pdf
[Meirelles et al. 2022] Meirelles, A.C.O. et al. (2022). Don't let me down: West Indian manatee, Trichechus manatus, is still Critically Endangered in Brazil. Journal for Nature Conservation, 67, 126181. https://www.sciencedirect.com/science/article/abs/pii/S1617138122000425