Red-bellied Piranhas tend to travel in schools of 20 or more individuals.
They are important scavengers in their Amazon River ecosystems, and a large part of their diet comes from fins nipped from the tails of larger fish.
There are also alpha males among red-bellied piranhas. In mock battles for ranking, they bite into the water just before their opponent and make grunting noises to prove their superiority.
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Red-bellied piranhas communicate with each other through aggressive behaviors (biting, chasing, fighting) and through sounds made by their sonic muscles. While they are hunting prey, these sharp-toothed fish create sounds based on the intensity of the pursuit.
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Piranhas spawn during the rainy season from December through March.
Female piranhas will lay eggs near water plants, onto which the eggs stick. The males then fertilize the eggs. After just two to three days the eggs will hatch.
Several thousand eggs
Adult piranhas will swim side-by-side in small circles, sometimes with two individuals swimming in opposite directions while keeping their ventral surfaces close to one another. Although this may appear to be a courtship display, a closer look reveals that the adults are actually defending nesting sites.
Spawning - Eggs and Fertilization - Hatching - Juvenile Piranhas - Adult Piranhas
Piranhas are usually able to breed by the time they are 1 year old.
In Tropical rivers and murky water
The newly hatched piranhas, known as fry, rely on a yolk sac for nutrition during the first days of life. As they mature, the juvenile fish use water plants as cover and survive on small crustaceans, worms and insects.
Visually you may see the difference only due to continuous observations of the fish behavior, especially during the spawning period. Males become more brightly colored, and the females’ abdomen becomes rounded.