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Brazil. Something went wrong, and the bus suddenly broke loose and rolled off the

ferry and into the river. Some of the 38 passengers were injured in the fall but for most

of them the accident itself was not fatal. The real horror came later. It took several

hours for help to arrive, and when at last the rescuers reached the bus, they found that

only a few of the passengers were still alive. Of the others, only their bones remained.

They had been eaten by piranhas.

     For a man-eater, the piranha is not very big: most are only about a foot in

length. But these little fish are designed for efficient killing, with powerful jaws and

teeth as sharp as knives. They live in the rivers and lakes in many parts of South

America, and generally feed in large schools—which is why they can do so much

damage. One of these small fish could bite off your finger, bone and all, so you can

imagine the effect of a hundred or so, all attacking at the same time, mad with hunger.

     These fish are attracted by blood, and there were many stories of wounded

animals being attacked and eaten in a few seconds, as they attempted to cross a stream

infested with piranhas. People with cuts and scratches have gone swimming in the

water and have been attacked. In some places, where cow-boys want to move a herd of

cattle across a dangerous stream, they will first go down-river and shoot an alligator or

throw meat into the river, to divert the attention of the piranhas while the cattle are

rushed across the river some distance away.

With such a reputation, you might imagine that no one ever enters the inland

waters of South America. But this is not so. In fact, the piranhas are not always

aggressive, and in some places people fish and swim freely in the water, although not if

they have wounds. It seems that the piranhas’ behavior varies according to certain

factors, and that they are less likely to be aggressive in deeper water, and where there is

a plentiful supply of other fish for them to feed on. But in times of drought, as the

water level falls, the piranhas become crowded together. When their natural food

supply diminishes, they are likely to become more and more dangerous. There have

even been reports of piranhas leaping out of the water to bring down and devour birds

flying low over the surface.