Amazonian manatees are aquatic mammals and live almost entirely underwater. Indeed the three manatee species and the closely related dugong are unique in that they are the only plant-eating marine mammals (8). They feed entirely on aquatic vegetation near lake edges, such as emergent grasses, water lettuce and floating vegetation. Shy and secretive, only their nostrils protrude from the surface of the water to breathe as they search for lush vegetation (8). Despite being slow grazers they are able to consume up to eight percent of their body weight in one day (2) (8). Most feeding occurs during the wet season, when they graze upon new plant growth in seasonally flooded water. During the dry season, individuals return to the main water courses, or to deep flooded backwaters where herds congregate (8). Here they may not eat for weeks or months due to the lack of food. However, manatees have large fat reserves and slow metabolic rates; at one third of the usual rate for a mammal of its size. This enables them to survive until the water levels rise again and food becomes more abundant (2) (8).
These mammals are active by day and night. They are found individually or in small groups of between four and eight animals (8). Mothers nurse their calves from a teat behind the flipper, and it is the mothers and calves that form the closest bonds (8) (9). A single calf is born after a gestation period of approximately 13 months. It is dependant on its mother for a considerable time, so interbirth intervals may be as long as three and a half years or more. Individuals mature at five or six years of age and members maintain group contact by underwater vocalisations (9). The lifespan of this animal is unknown, but individuals have lived past twelve and a half years in captivity (8).