Picture pushing a block of clay against a wall. The clay next to the wall would be crunched upward.. The area behind where it was pushed up would buckle downward. That corresponds to the formation of the Amazon Basin, a depression in the earth that runs the length of South America east of the Andes.. It left behind a thick, rich lake bed that is now a grass- and forest-covered plain with many thousands of rivers and lakes.
This huge Amazon Basin, with its lush plant life and many bodies of fresh water, is the biggest basin in the world and home to a vast number of fish species, including the piranhas. Piranhas are found in much of South America-but nowhere else in the world, at least not naturally.
The fish range from Venezuela south to the northern part of Argentina. They are found in all the major South American rivers that flow to the Atlantic Ocean, including the Amazon, Orinoco, Essequibo, La Plata, and Soa Francisco. Piranhas are lowland fish that live in both big rivers and small streams. They also inhabit lagoons, ponds, lakes, and reservoirs. They live in fresh waters in both tropical forests and tropical savannas, or grasslands.
Piranhas do not live in mountain streams or lakes, probably because the water is much too cold and flows too swiftly to allow the fish to catch what little food there is in such places. South America’s climate can vary greatly from one region to another, from the hot deserts of Chile to the cold peaks of the Andes. Since the continent crosses the equator, most of South America is warm most of the time. Rather than having a true summer or winter, the tropics have a rainy season and a dry season. And the piranha’s world is quite different from one season to another. The heavy rains start very suddenly and slowly taper off months later. Some areas that are flat and grassy in the dry season become covered with water in the wet season.
These flood plains are home to a huge number of animals-ducks, storks, herons, turtles, crocodiles, snakes, and capybaras (the biggest rodents-more than 4 feet [1.2 meters] long). And of course, there are lots of fish-catfish, stingrays, electric eels, and many more, including piranhas and pacus. Some animals prey upon piranhas. Many fish, birds, and other animals that live in or near water eat small or young piranhas. The large piranhas have fewer predators, but even they can make a meal for wading birds, giant otters, river dolphins, large catfish, and caimans (South and
Central American alligators)-as well as for humans. During the rainy season, South American rain forests in lowland areas often flood, creating swamps. These areas, called flooded forests, are underwater up to ten months of the year, and the plants have all kinds of special features that allow them to survive being underwater for so long. After the rain stops, the flooded areas gradually dry and the water level of rivers, streams, lagoons, and water holes drops, crowding the fish into smaller and smaller areas.
Wary Neighbors(Piranhas at Home)
In almost any place where there is one kind of piranha, there will be several other species, too. Usually, three or more species of piranhas can be found in the same area. Different kinds of piranhas may bite at one another. Piranhas are usually most active during the day. Different species, though, sometimes hunt at different times. This may keep the several sorts of piranhas in a body of water from competing for the same food at the same time. It may also prevent them from eating one another.
Even within the same species, piranhas of different ages may be active at different times. At night, younger, smaller fish tend to rest among the water plants, leaving the open waters to older and bigger fish.
This prevents adult piranhas from making a meal of young fish. By about 10.00 PM ,even the largest piranhas has usually retired for the night. Some kinds of piranhas gather in groups .others swim alone .they may pick out an area and patrol it, checking it for food .At night or when they are resting they hide among plants in the shallow water .
A Skilled Hunter
At first glance, it may seem that piranhas just swim around in a group, eating anything at any time. But in fact, piranhas use many different hunting methods. They may hide among plants or rocks, waiting for prey to come close. Then they rush out and capture or bite it. They might sneak up on their prey. They might even act as if they’re not interested in a fish until they’re close enough to reach it. Some piranhas that look like the fish they eat approach in disguise, behaving like one of their targets until they get close enough to grab a bite. Some fins, and kinds tails, of piranhas, are slimmer like the and ones faster that than eat scales, other.
species, and they chase down other fish. Most piranhas, however, aren’t fast enough to catch fish racing through open water. Some piranhas behave like lions that hunt zebras or antelope. A scientist saw a group of scaleeating piranhas hunting a school of fish. One piranha rushed in and scattered the group of prey fish. Then each piranha picked out one fish to bite some scales from. Piranhas will also take advantage of the confusion when other hunting fish scatter a school. Piranhas also scavenge, searching for bits of flesh and dead animals. Many aquatic animals such as catfish and crabs are scavengers, but when the piranhas come, they back away and let the piranhas eat.
Avoiding the Hunters
Some fish have evolved behaviors or features that lessen their chances of being attacked by piranhas. Fish that are preyed on by fin-eating piranhas may hide their tails in plants. Some of these, such as the Oscar, have a circular mark near their tail that looks very much like an eye. This false eye probably confuses piranhas, and therefore they do not attack. Some schools of fish have one fish keep watch while the rest eat. Sometimes prey fish fight back, or a group of them might rush toward a piranha and chase it away. Many other fish avoid piranhas by coming out only at night. Most piranhas have some red coloring on their body.
Many of the fish that piranhas eat also have red coloring. The red color might fool the piranha into thinking the other fish is one of its own kind and give the fish a chance to escape. Or the red color might make other fish avoid eating the red fish, mistaking it for a piranha. Scientists aren’t entirely sure what the purpose of this particular mimicry is. Lords of the Water Piranhas are very important fish in the freshwater ecosystem of the Amazon Basin and throughout most of South America. Because they are such successful predators, their behavior affects the way other prey fish behave and perhaps even how they look. It’s easy to see why piranhas are sometimes called “lords of the water.”
