Amazonian Manatee

The Amazonian manatee is the smallest species of manatee and the only sirenian species living exclusively in freshwater. It inhabits the Amazon River basin, where it grazes on aquatic vegetation. Unlike its marine relatives, it lacks nails on its flippers, hence the species name 'inunguis'. It is remarkable for its adaptation to the seasonal flood cycles of the Amazon, moving between flooded forests and river channels.

Brazil, Peru, Colombia, Ecuador

Found throughout the Amazon basin in Brazil, Peru, Colombia, and Ecuador, extending into the upper Amazon tributaries. Its range follows the extent of the Amazon River and its major tributaries, generally absent from fast-flowing or turbulent waters.

Altitude and depth

Lowland freshwater systems, typically below 300m elevation; water depth used ranges from 1 to 10 meters.

Seasonal movements

Exhibits seasonal movements tied to the Amazon's flood pulse, moving into flooded forests during high water season to feed and retreating to deeper river channels and lakes during low water season when food is scarcer.

Exclusively freshwater habitats including slow-moving rivers, oxbow lakes, flooded forests (varzea), and blackwater lagoons within the Amazon basin. It prefers areas with abundant floating and submerged vegetation and calm waters.

Adaptations to its environment

Possesses a low metabolic rate and can survive months with reduced food intake during low water season by relying on fat reserves. Its lack of nails and reduced bone density are adaptations for a purely aquatic freshwater lifestyle, and its skin folds allow expansion during feeding on abundant vegetation.

Classified as Vulnerable (VU) by IUCN due to ongoing population decline estimated at over 30% over three generations, driven primarily by historic and ongoing hunting pressure combined with habitat degradation.

Estimated population

Estimated at fewer than 10,000 mature individuals, with a continuing declining trend across much of its range.

Illegal hunting for meat and oil, incidental entanglement in fishing gear, habitat degradation from deforestation and dam construction, and pollution from agricultural runoff and mining activities.

Diseases and parasites

Susceptible to skin parasites, barnacles-like organisms in some populations, and various internal parasites; disease is not a major known threat but can affect stressed or captive individuals.

Protected under Brazilian and other national wildlife laws prohibiting hunting; rehabilitation and reintroduction programs exist, notably run by INPA in Manaus, Brazil. Several protected areas and reserves within the Amazon basin provide partial habitat protection.

Recommended actions

Strengthen enforcement against illegal hunting, expand protected freshwater habitats, promote community-based conservation and awareness programs, and support rehabilitation and release initiatives for orphaned calves.

Smooth, wrinkled grey to black skin often with a distinctive pale pink or white patch on the belly, a rounded paddle-like tail, and no nails on the flippers (unlike other manatee species). The body is fusiform and streamlined, adapted for slow aquatic movement.

Size

Body length typically ranges from 2.5 to 3 meters.

Weight

Adults weigh between 350 and 500 kg, with some individuals reaching up to 480 kg.

Distinctive features

Distinguished from West Indian and West African manatees by its smaller size, lack of nails on flippers, exclusively freshwater habitat, and often a pale ventral patch.

Differences between males and females

Minimal sexual dimorphism; females are sometimes slightly larger than males, but external differences are subtle.

Generally solitary or found in small, loose groups, though mother-calf pairs are the most stable social unit. Larger aggregations may occur temporarily at abundant feeding sites.

When it is active

Primarily active during daylight hours (diurnal), spending much of the day feeding and resting near the water surface or bottom.

Diet

Strict herbivore feeding on a wide variety of aquatic and floating vegetation including water hyacinth, grasses, and floating macrophytes, consuming up to 8% of its body weight daily.

Communication

Communicates through low-frequency vocalizations such as squeaks and chirps, especially between mothers and calves, along with tactile interactions.

Interactions with other species

Has few natural predators as an adult, though jaguars and caimans may prey on young calves; interacts ecologically with fish and turtles that may follow manatees to feed on stirred-up vegetation and parasites removed from their skin.

Role in its ecosystem

Plays an important ecological role as a grazer that helps control aquatic vegetation growth, maintaining waterway health and influencing nutrient cycling within the Amazon floodplain ecosystem.

Breeding can occur year-round but often peaks during the flood season; gestation lasts about 12-14 months, typically resulting in a single calf.

Raising the young

Calves are cared for exclusively by the mother, nursing for up to two years while also learning to forage on vegetation; the bond between mother and calf is strong and prolonged.

Maturity and lifespan

Sexual maturity is reached around 4-5 years of age; lifespan can reach 30 years or more in the wild, with similar longevity in captivity under good care.

Classification

Mammalia > Sirenia > Trichechidae > Trichechus > Trichechus inunguis

Scientific synonyms

Manatus inunguis, Trichechus inunguis inunguis

Recent studies

Recent studies using satellite tagging and genetic analysis have revealed detailed information on seasonal movement patterns and population connectivity across different Amazon tributaries.

Genome and DNA

Diploid chromosome number is 2n=56, similar to other Trichechus species; genetic studies have helped clarify population structure across the Amazon basin.

Compared with similar species

Compared to the West Indian manatee (Trichechus manatus), the Amazonian manatee is smaller, lacks nails on its flippers, and is restricted to freshwater rather than coastal marine and estuarine habitats.

The Amazonian manatee is the only manatee species that never enters saltwater. It can survive for months during the dry season with minimal feeding by relying on stored body fat, and calves are known to vocalize distinct squeaks to stay in contact with their mothers.

Where and how to see it

Best observed in protected reserves such as the Mamirauá Sustainable Development Reserve in Brazil, especially during the flood season when manatees move into flooded forests; early morning boat tours with experienced guides increase chances of sightings.

Risks to humans

No notable risk to humans; manatees are gentle and non-aggressive herbivores.

Human uses

Historically hunted for meat, oil, and hide by local communities, though this is now illegal in most range countries; currently the species has ecotourism value in some protected reserves.

Myths and legends

In Amazonian folklore, manatees are sometimes associated with river spirits or mermaid-like legends, and indigenous communities have traditional stories linking them to fertility and water spirits.