Peixe-boi (Brazil), Sea cow, South American manatee, Amazon manatee
The Amazonian manatee (Trichechus inunguis) is a large aquatic mammal with a bizarre appearance, first described as "a curious combination of a seal and a hippopotamus". It is the smallest of the three extant species of manatee. Manatees are often known as sea cows which is a reference to their slow, peaceful, herbivorous nature, reminiscent of that of bovines.
The Amazonian manatee can be distinguished by its smoother rubbery skin and lack of vestigial nails on its flippers. Manatees have forelimbs modified into flippers, no free hind limbs, and the rear of the body in the form of a flat, rounded, horizontal paddle. The flexible flippers are used for aiding motion over the bottom, scratching, touching, and even embracing other manatees, and moving food into and cleaning the mouth. The manatee's upper lip is modified into a large bristly surface, which is deeply divided. It can move each side of the lips independently while feeding. The general coloration is grey, and most Amazonian manatees have a distinct white or bright pink patch on the breast. Their teeth are continuously replaced horizontally from the caudal portion of the jaw to the rostral portion throughout the manatee's life, a unique trait among mammals.
Amazonian manatees occur throughout the Amazon Basin in northern South America (Colombia, Ecuador, Peru, and Brazil). They live in freshwater oxbows, blackwater lakes, and lagoons which have deep connections to big rivers and plenty of aquatic vegetation.
Amazonian manatees are gregarious animals and used to occur in big herds. Due to severe overhunting, however, groups seen today number only 4 to 8 individuals. These manatees are both nocturnal and diurnal and they live their lives almost entirely underwater. Only their nostrils stick up above the water as they search the bottoms of rivers and lakes for lush vegetation. An individual in one day can eat as much as eight percent of its body weight of aquatic vegetation. Manatees have nostrils, not blowholes like other aquatic mammals, which close when underwater to keep water out and open when above water to breathe. They can remain underwater for extended periods but usually surface for air about every five minutes. Manatees make seasonal movements that depend on the flood regime of the Amazon Basin. They are found in flooded forests and meadows during the flood season when food is abundant. Amazonian manatees vocalize alone and with others, particularly between cows and their calves.
Amazonian manatees are herbivores (graminivores, folivores). They eat a wide vriety of aquatic plants such as "water lettuce", grasses, bladderworts, hornworts, water lilies, and particularly, water hyacinths. They are also known to eat palm fruits that fall into the water.
Mating herds form that consist of a male and a few females. The females have the freedom to leave their herd and so may mate with another male, meaning that Amazonian manatees may have a polyandrous mating system. Breeding can take place throughout the year, with peaks occurring at different times in various parts of the system of rivers. In the central Amazon, births mostly occur in February-May, which is when water levels rise. A single young is born after gestation of around one year. Births occur at 2-3 year intervals. Young are very well looked after by their mothers, who will nurse them up to the age of 18 months. Males are 5 to 6 years old when they first mate, and females much younger, with their average age being about 3 years old.
Once occurring in large herds and with healthy population numbers, Amazonian manatee numbers have decreased due to extensive hunting by commercial and subsistence hunters. It has been hunted for meat, fat, and oil, and in the past for its hide, for use as machine belts and water hoses. Current threats include hunting and drowning accidentally in commercial fishing nets. Large areas surrounding the manatee’s river habitats being deforested has also caused the soil to erode, as well as degradation of food sources and reduction in vegetation in the waterways.
Although manatees are widespread through a large area, there is a high level of uncertainty about total population size. According to the IUCN Red List resource, a minimum of 10,000 individuals was estimated in 1977 for the Amazon Basin as a whole. Currently Amazonian manatees are classified as Vulnerable (VU) and their numbers today continue to decrease.
