Fish and Mammals of the Amazonian River

Giant Otter:

The Giant Otter are very large otters and the longest examples of the weasel family. The male otters grow up to six feet. Their diet mostly consists of fish and crabs, which they hunt in family groups of three to eight members. Don’t be fooled by their cute looks, they are more than a match for the other animals on this list, with groups of otters having been spotted killing and eating an anaconda. They hold their own against caiman as well. One family was seen devouring a five foot caiman, which took them about 45 minutes. They are an endangered species, mainly due to human intervention. They are among the most capable predators in the Amazon rain forest, hence their local name of "river wolves".
  

Black Caiman:

                                                                              The Black Caiman is basically an alligator on steroids. They can grow up to twenty feet long, with bigger, heavier skulls than Nile crocodiles, and are the top predators in the Amazonian waters. That means they are basically the kings of the river and can eat nearly anything they can get their teeth into, including piranhas, monkeys, perch, deer, and anacondas. Oh, and yes, they totally attack humans. In 2010, a biologist named Deise Nishimura was attacked by a caiman while cleaning something on her houseboat, and while she managed to fight it off, it bit off her leg. This particular caiman had been living under her houseboat for eight months, waiting for the chance to strike.

Red-Bellied Piranha:

                                                   
The Red-Bellied Piranhas are so widely feared that they have inspired a number of Hollywood movies. Red-bellied piranhas are actually primarily scavengers. That’s not to say they won’t attack healthy creatures. Red-Bellied Piranhas can grow to be over 12 inches long and swim around in large groups. They tend to be more than a match for most animals. Like all piranhas, red-bellies have incredibly sharp teeth, one row on each of their powerful upper and lower jaws. These teeth are interlocking, which makes them perfect for tearing the flesh of their prey. Their fearsome reputation mainly comes from sights of their “feeding frenzies,” where groups of piranhas will congregate on their unlucky prey and strip it to the bone within minutes. These attacks are rare and are usually the result of starvation or provocation.

Pink River Dolphin:

The Pink River Dolphins are not the same dolphins that you would see in the ocean; they have special adaptations to their habitat. In fact, river dolphins are only distantly related to sea dolphins. These friendly, sensitive, mammals with a brain capacity 40% larger than that of humans, have lived in harmony with the people of the Amazon, but now, face extinction. What was considered to be one of the least threatened species of dolphins 20 years ago, has now become one of the most endangered species due to the destruction of the South American tropical rainforest. No one knows the actual number of that live in the Amazon basin, but according to the research and studies the number of pink dolphins from 18 years ago has risen from eight pink dolphins on the Yarapa River to 35 to 45.