亚马逊海牛是目前存活的海牛类中体型最小的。体型上较以上两种海牛小且修长。在腹部及胸前有特殊的白色色块，体色也较深。亚马逊海牛的另一项特色是在前鳍上没有指甲。纪录中最大的亚马逊海牛身长约2.8公尺，重量为479公斤。亚马逊海牛是唯一海牛目哺乳动物中生活在淡水水域
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亚马逊海牛
学名 -英文名：
Trichechus inunguis Natterer, 1883 - Amazonian manatee
特征描述：
Amazonian manatees are the smallest, most slender of the 3 species of manatees. They have the rounded tails characteristic of manatees, but the skin of adults and juveniles is smooth, rather than wrinkled as in their relatives. The large flippers lack nails. There are thick bristles on the lip pads of both jaws, and the body has a sparse covering of fine hairs. Amazonian manatees are grey to black; most have white or pink belly and chest patches (these only rarely occur in Florida manatees). Five to 7 functional cheek teeth, and 2 vestigial incisors (resorbed after birth) are found in each tooth row. Typical of manatees, teeth are replaced from the rear. They are smaller than in other manatee species.
容易混淆为：
Amazonian and West Indian manatees may co-occur in or near the mouth of the Amazon River. The size, shape, and coloration differences listed above will help in allowing them to be distinguished. Also, the presence (West Indian) or absence (Amazonian) of nails on the flippers is diagnostic, when seen.
个体大小：
Amazonian manatees reach lengths of only about 3.0 m, and weights of at least 450 kg. Length at birth is about 90 cm; weight is 10 to 15 kg.
地理分布：
This is a freshwater species. Amazonian manatees are found in waters of the Amazon River and its tributaries in Brazil, Guyana, Colombia, Peru, and Ecuador. They may possibly occur in the Orinoco drainage as well.
生物学及行为：
The poorly known Amazonian manatee occurs singly or in feeding groups of up to 8 individuals. The large herds often seen in the past are a rarity today. Their activities are strongly influenced by the seasonal floods. Their behaviour is very cryptic. Breeding occurs throughout much of the year, but there is a peak in February to May, when the water level in the river rises. A single calf is born after a gestation of about a year. Amazonian manatees feed on vascular aquatic and semi-aquatic plants, but they have also been observed to eat floating palm fruits. Some may fast or eat dead plant material during the dry season.
利用价值：
Heavy hunting for meat, hides, and oil in the 17th to mid-20th century has left the species depleted in many areas. Subsistence hunting continues to pose a threat, and damming of tributaries and other forms of habitat destruction create other problems.
IUCN等级：
Vulnerable.
异名：
Trichechus inunguis Natterer, 1883
俗名：
Amazone zeekoe [荷兰语] Amazonian manatee [英语] Lamantin de l'Amazonie [法语] Vaca marina del Amazon [西班牙语]
FAO物种代码：
TRIC Tric 3 [FAO Species code] SEW [FAO Species code]
