10 Unique Animals of the Amazon River Basin

The Amazon River basin, which includes the Amazon Rainforest, covers almost three million square miles and overlaps the boundaries of nine countries: Brazil, Colombia, Peru, Venezuela, Ecuador, Bolivia, Guyana, Suriname, and French Guiana. By some estimates, this region is home to one-tenth of the world's animal species. They include everything from monkeys and toucans to anteaters and poison dart frogs.

01
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Piranha

Piranhas
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There are many myths about piranhas, such as the idea that they can skeletonize a cow in less than five minutes. The fact is that these fish don't even particularly like to attack humans. Still, there's no denying that the piranha is built to kill, equipped as it is with sharp teeth and extremely powerful jaws, which can chomp down on prey with a force of over 70 pounds per square inch. Even more terrifying is the megapiranha, a giant piranha ancestor that haunted the rivers of Miocene South America.

02
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Capybara

Capybara
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Weighing up to 150 pounds, the capybara is the world's largest rodent. It has a wide distribution across South America, but the animal especially likes the warm, humid environs of the Amazon River basin. The capybara subsists on the rain forest's copious vegetation, including fruit, tree bark, and aquatic plants, and has been known to congregate in herds of up to 100 members. The rain forest may be endangered, but the capybara isn't; this rodent continues to thrive, despite the fact that it's a popular menu item in some South American villages.

03
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Jaguar

Jaguar
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The third-largest big cat after the lion and the tiger, the jaguar has had a difficult time over the last century, as deforestation and human encroachment have restricted the animal's range across South America. However, it's much harder to hunt a jaguar in the dense Amazon River basin than out in the open pampas, so the impenetrable portions of the rain forest may be Panthera onca's last, best hope. No one knows for sure, but there are at least a few thousand jaguars preying on the megafauna of the Amazon rain forest; an apex predator, the jaguar has nothing to fear from its fellow animals (except, of course, human beings).

04
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Giant Otter

Giant Otter
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Also known as "water jaguars" or "river wolves," giant otters are the largest members of the mustelid family, and closely related to weasels. The males can grow up to six feet long and weigh up to 75 pounds, and both sexes are known for their thick, glossy coats—which are so coveted by human hunters that there are only about 5,000 giant otters left across the entire Amazon River basin. Unusually for mustelids (but fortunately for poachers), the giant otter lives in extended social groups consisting of about half a dozen individuals.

05
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Giant Anteater

Giant Anteater
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So large that it's sometimes known as the ant bear, the giant anteater is equipped with a comically long snout—ideal for poking into narrow insect burrows—and a long, bushy tail; some individuals can approach 100 pounds in weight. Like many of the plus-sized mammals of tropical South America, the giant anteater is severely endangered. Fortunately, the vast, swampy, impenetrable Amazon River basin affords the remaining population some level of protection from humans (not to mention an inexhaustible supply of tasty ants).

06
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Golden Lion Tamarin

Golden Lion Tamarin
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Also known as the golden marmoset, the golden lion tamarin has suffered terribly from human encroachment. By some estimates, this New World monkey has lost a whopping 95 percent of its South American habitat since the arrival of European settlers 600 years ago. The golden lion tamarin only weighs a couple of pounds, which makes its appearance all the more striking: a bushy mane of reddish-brown hair surrounding a flat, dark-eyed face. (The distinctive color of this primate likely comes from a combination of intense sunlight and an abundance of carotenoids, the proteins that make carrots orange, in its diet.)

07
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Black Caiman

Black Caiman
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The largest and most dangerous reptile of the Amazon River basin, the black caiman (technically a species of alligator) can approach 20 feet in length and weigh up to half a ton. As the apex predators of their lush, humid ecosystem, black caimans will eat pretty much anything that moves, ranging from mammals to birds to their fellow reptiles. In the 1970s, the black caiman was seriously endangered—targeted by humans for its meat and its valuable leather—but its population has since rebounded.

08
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Poison Dart Frog

Poison Dart Frog
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As a general rule, the more brightly colored a poison dart frog, the more powerful its venom—which is why the predators of the Amazon River basin stay far away from iridescent green or orange species. These frogs don't manufacture their own venom but collect it from the ants, mites, and other insects that constitute their diet (as evidenced by the fact that poison dart frogs kept in captivity, and fed other types of food, are much less dangerous). The "dart" part of this amphibian's name derives from the fact that indigenous tribes across South America dip their hunting darts in its venom.

09
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Keel-Billed Toucan

Keel-Billed Toucan
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One of the more comical-looking animals of the Amazon River basin, the keel-billed toucan is distinguished by its enormous, multi-colored bill, which is actually much lighter than it appears at first glance (the rest of this bird is comparatively muted in color, except for its yellow neck). Unlike many of the animals on this list, the keel-billed toucan is far from endangered. The bird hops from tree branch to tree branch in small flocks of six to 12 individuals, the males dueling each other with their protruding schnozzes during mating season (and presumably not inflicting a whole lot of damage).

10
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Three-Toed Sloth

Three-Toed Sloth
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Millions of years ago, during the Pleistocene epoch, the rain forests of South America were home to giant, multi-ton sloths like Megatherium. Today, one of the most common sloths of the Amazon River basin is the three-toed sloth, Bradypus tridactylus, which is characterized by its greenish, algae-crusted fur, its ability to swim, its three toes, and its agonizing slowness—the average speed of this mammal has been clocked at about a tenth of a mile per hour. The three-toed sloth coexists with the two-toed sloth, and these two animals will sometimes even share the same tree.