The Amazonian manatee is the only sirenian that lives its entire life in fresh water, and it is found nowhere on Earth except the Amazon Basin [IUCN 2016] [Society for Marine Mammalogy 2018]. A slow-moving, fully aquatic herbivore, it spends its days grazing on floating and emergent plants in the rivers, lakes, and seasonally flooded forests of northern South America [Rosas 1994]. Centuries of commercial harvest for meat, hide, and oil left the species rare across much of its historic range, and continued hunting paired with one of the slowest reproductive rates among mammals keeps it among the most at-risk large animals of the basin [IUCN 2016] [Rosas 1994].
Its scientific name, inunguis, means "without nails," referring to the absence of nails on its flippers — a feature that distinguishes it from the West Indian and African manatees [Gorog 1999].
Biology and Identification
The Amazonian manatee is a stout, fusiform mammal with a rounded, paddle-shaped tail and nailless front flippers. Adults typically measure about 1.6–2.3 m in length and weigh roughly 120–270 kg, with the largest recorded individuals approaching 380 kg [Best 1984] [Gorog 1999]. The skin is smooth and gray to brownish, and most individuals carry distinctive white or pink markings on the chest and belly that help researchers tell animals apart [Gorog 1999]. Fine hairs cover the body and stiff bristles ring the mobile, divided upper lip used to gather vegetation.
It is an obligate herbivore. Free-ranging animals feed on aquatic macrophytes — water lettuce, water hyacinth, floating grasses, and other plants — and can consume on the order of 8% of their body mass in vegetation each day [Best 1984] [Gorog 1999]. Reproduction is slow: gestation lasts roughly a year (about 328 days), females usually bear a single calf, and births are concentrated during the rising-water season when flooded forests offer abundant forage [Gorog 1999] [Best 1984]. These traits, combined with a long generation time estimated at about 25 years, mean populations recover only gradually from losses [IUCN 2016].
Habitat and Range
Trichechus inunguis is endemic to the Amazon Basin and is the only manatee restricted to fresh water [IUCN 2016] [Society for Marine Mammalogy 2018]. Its range spans the Amazon River drainage across Brazil, Peru, Colombia, and Ecuador, with the basin covering on the order of seven million square kilometers, though the species occupies this area patchily [IUCN 2016]. Animals concentrate in nutrient-rich whitewater channels, oxbow lakes, lagoons, and seasonally flooded forests (várzea), moving seasonally as water levels rise and fall [Rosas 1994] [Gorog 1999].
This dependence on the flood pulse makes the species sensitive to the basin's hydrological cycle. During severe dry seasons, manatees can become confined to shrinking pools, where forage is scarce and the animals are easier to locate [IUCN 2016]. To protect a sensitive species, NRWL describes distribution only at the regional and country scale and does not publish specific aggregation sites.
Conservation Status
The Amazonian manatee is currently assessed as Vulnerable on the IUCN Red List, in an assessment published in 2016 (criteria A3cd) [IUCN 2016]. The listing reflects a suspected population decline of at least 30% over the next three generations — roughly 75 years given an estimated 25-year generation length — driven primarily by continued hunting, rising incidental calf mortality, and habitat degradation [IUCN 2016]. The population trend is reported as decreasing, and a reliable basin-wide population figure does not exist because the turbid water and dense vegetation make the species extremely difficult to survey [IUCN 2016] [Franzini et al. 2013]. The species is listed on Appendix I of CITES, which prohibits international commercial trade [IUCN 2016].
Threats
Hunting remains the dominant pressure. The species was commercially exploited for centuries, and subsistence and opportunistic hunting for meat continue across much of the range despite national legal protection, in part because enforcement is limited [Rosas 1994] [IUCN 2016]. Incidental mortality is also significant: animals drown in gillnets, and calves are sometimes captured or orphaned [IUCN 2016] [Souza et al. 2021]. Habitat degradation from fisheries, river traffic, mining, and pollution affects water quality and forage availability [IUCN 2016]. Increasingly, severe droughts linked to climate variability strand and concentrate manatees, raising both natural mortality and exposure to hunting [IUCN 2016].
What Is Being Done
The Amazonian manatee is legally protected in all four countries where it primarily occurs, and CITES Appendix I status restricts international trade [IUCN 2016]. Protected areas in the central Amazon — including sustainable-use reserves where local communities participate in management — help safeguard key habitat, and research with riverine communities has documented local knowledge useful for conservation planning [Franzini et al. 2013]. Rescue and rehabilitation programs care for orphaned and injured calves with the goal of returning healthy animals to the wild; a study of rehabilitation in the Peruvian Amazon analyzed the clinical factors affecting survival of rescued individuals to improve outcomes [Souza et al. 2021]. Long-term research at institutions in Brazil and Peru continues to refine survey methods and population monitoring for this hard-to-observe species [Franzini et al. 2013].
How You Can Help
You can support the Amazonian manatee by learning about the species and sharing accurate, sourced information rather than sensational claims. Supporting reputable organizations and protected areas that fund Amazon manatee research, habitat protection, and rehabilitation contributes to long-term monitoring and recovery work [IUCN 2016] [Souza et al. 2021]. Because so much about the species' numbers remains uncertain, public attention to verified science helps sustain the surveys and protected areas on which its future depends.
References
[IUCN 2016] Marmontel, M., de Souza, D. & Kendall, S. (2016). Trichechus inunguis (Amazonian Manatee). The IUCN Red List of Threatened Species 2016: e.T22102A43793736. https://www.iucnredlist.org/species/22102/43793736
[Rosas 1994] Rosas, F.C.W. (1994). Biology, conservation and status of the Amazonian Manatee Trichechus inunguis. Mammal Review, 24(2): 49–59. https://doi.org/10.1111/j.1365-2907.1994.tb00134.x
[Gorog 1999] Gorog, A. (1999). Trichechus inunguis (Amazonian manatee). Animal Diversity Web, University of Michigan Museum of Zoology. https://animaldiversity.org/accounts/Trichechus_inunguis/
[Best 1984] Best, R.C. (1984). The aquatic mammals and reptiles of the Amazon. In: Sioli, H. (ed.) The Amazon: Limnology and Landscape Ecology of a Mighty Tropical River and its Basin, pp. 371–412. Dr W. Junk Publishers. https://doi.org/10.1007/978-94-009-6542-3_14
[Franzini et al. 2013] Franzini, A.M., Castelblanco-Martínez, D.N., Rosas, F.C.W. & da Silva, V.M.F. (2013). What do local people know about Amazonian manatees? Traditional ecological knowledge of Trichechus inunguis in the oil province of Urucu, AM, Brazil. Natureza & Conservação, 11(1): 75–80. https://doi.org/10.4322/natcon.2013.012
[Souza et al. 2021] Souza, D.A., Gonçalves, A.L.S., Marmontel, M. et al. (2021). Factors influencing survival of rescued Amazonian manatees (Trichechus inunguis) during clinical rehabilitation in Peru. Conservation Science and Practice. https://doi.org/10.1111/csp2.70235
[Society for Marine Mammalogy 2018] Society for Marine Mammalogy. Trichechus inunguis (Amazonian manatee) species fact sheet. Committee on Taxonomy. https://marinemammalscience.org/facts/trichechus-inunguis/
[CITES 2023] CITES. Trichechus inunguis — Appendix I. Convention on International Trade in Endangered Species of Wild Fauna and Flora. https://cites.org/eng/app/appendices.php
[Animal Diversity Web 2024] University of Michigan Museum of Zoology. Animal Diversity Web species account: Trichechus inunguis. https://animaldiversity.org/accounts/Trichechus_inunguis/