Red-bellied piranha

The Red-Bellied Piranha (Pygocentrus nattereri) is the most dangerous type of Piranha. Piranhas have short, sharp, powerful teeth. These fish mostly live together, because alone they are vulnerable, but together they are almost invincible. For the most part, Red-Bellied Piranhas are carnivores and scavengers. 

Anatomy
Piranhas are fresh water fish with a vicious appetite. They mostly live in south America and the Andes Mountains. Piranhas are meat eating creatures, but are very ferocious. They swim in packs of 20 piranhas and go crazy when food comes along. They usually are usually yellow, red, black, and gray. They grow from half a foot to two feet long. Their faces resemble those of bulldogs. Piranhas teeth are like humans, they grow back throughout their lives. Their teeth are obviously super sharp because of their ability to feed so quickly.  These certain piranhas, however, have a very powerful bite, more powerful than normal piranhas.

Reproduction
Piranhas are old enough to have babies at only one years old. First, the females and males go through a courtship ceremony by swimming around each other. The female then lays thousands of eggs on nearby plants so they don't get lost. The nest are usually bowl shaped. The male comes and fertilizes them with sperm and the the eggs hatch in about 2-10 days. The females can lay about 5000 eggs. They can lay more eggs in only 2 or 3 weeks. The males then guard the eggs until they hatch. 

Ecology
The predators of the Red-Bellied Piranha are: Piranhas and Humans. Piranhas eat anything meat. They are carnivores and scavengers. That means they eat meat and they eat anything they can find. Since piranhas have so few predators, the only way that the population is maintained is because they eat each other. It also appears that the reason that Piranhas travel in schools is for defense purposes as well. 

Feeding Frenzy
Piranhas are most known for their incredible ability to eat animal flesh very quickly. Although, this does not happen with only one or two piranhas. It takes dozens of piranhas and a matter of minutes to reduce a fish to nothing but bone. Piranhas will eat about any meat though, even humans. Some even eat their own kids. Red Bellied Piranhas are the ones that are infamous for their aggression.  However, the piranhas most of the piranhas eat animals that are injured and will not put up as much of a fight. When they attack healthy animals it is usually because there is blood in the water.  Red-bellied piranhas are the only group of piranhas that can actually eat animals that quickly.