How many piranhas are there

These fish are only found in freshwater streams and rivers. They are mostly found in the Amazon Basin in South America. Piranhas prefer water that is swiftly moving. The water that they live in is usually degrees Fahrenheit, which is nice and warm. The only way that these fish would go after humans is because they feel threatened or they are especially hungry.

In captivity, piranhas can live longer than they would in the wild. The oldest known piranhas in captivity lived to eight years old. Whenever a female piranha lays eggs , they will usually number in the thousands. These eggs are then fertilized by a male and guarded over by the shoal.

More Animals facts. Please email or share this article! Email Pin FB. They will snap a finger off a hand incautiously trailed in the water; they mutilate swimmers—in every river town in Paraguay there are men who have been thus mutilated; they will rend and devour alive any wounded man or beast; for blood in the water excites them to madness.

They will tear wounded wild fowl to pieces; and bite off the tails of big fish as they grow exhausted when fighting after being hooked. Roosevelt went on to recount a tale of a pack of piranhas devouring an entire cow.

According to Mental Floss , locals put on a bit of a show for Roosevelt, extending a net across the river to catch piranhas before he arrived. After storing the fish in a tank without food, they tossed a dead cow into the river and released the fish, which naturally devoured the carcass.

A fish that can eat a cow makes for a great story. Though estimates vary, around 30 species inhabit the lakes and rivers of South America today. A study suggests that modern species diverged from a common ancestor around 9 million years ago. Also, the Atlantic Ocean rose around 5 million years ago, expanding into the flood plains of the Amazon and other South American rivers.

The high salt environment would have been inhospitable to freshwater fish, like piranhas, but some likely escaped upriver to higher altitudes. Genetic analysis suggests that piranhas living above meters in the Amazon have only been around for 3 million years. Piranhas attract a certain type of pet lover, and sometimes when the fish gets too large for its aquarium said pet lover decides its much better off in the local lake. In this manner, piranhas have shown up in waterways around the globe from Great Britain to China to Texas.

Piranhas are known for their razor-sharp teeth and relentless bite. Adults have a single row of interlocking teeth lining the jaw. True piranhas have tricuspid teeth, with a more pronounced middle cuspid or crown, about 4 millimeters tall. The actual tooth enamel structure is similar to that of sharks. But, while sharks replace their teeth individually, piranhas replace teeth in quarters multiple times throughout their lifespan, which reaches up to eight years in captivity. Though they are hardly as menacing as fiction suggests, piranhas do bite with quite a bit of force.

Using a tooth fossil model, they found that piranhas' million-year-old extinct ancestor, Megapiranha paranensis , had a jaw-tip bite force—the force that jaw muscles can exert through the very tip of its jaw—of as high as 1, pounds. For reference, the M. Science notes that T. Humans and capybaras are only part of the piranha diet if these prey are already dead or dying.

The idea that a piranha could rip a human to shreds is probably more legend than fact, too. For the curious, Popular Science spoke to some experts who estimate that stripping the flesh from a pound human in 5 minutes would require approximately to piranhas.

Cases of heart attack and epilepsy that ended with the afflicted drowning in a South American river do show evidence of piranha nibbles, but in those instances, the victim was already deceased when piranhas got involved.

In other words, they're a renewable food source: A piranha can repeatedly pluck scales off the same victim for years without killing it. The wimple piranha has turned the scale-grazing strategy into an art form.

Though the wimple spends its entire life eating scales, some other piranhas will only feed on them as juveniles. Native to the upper half of South America, the black piranha measures 8 to 15 inches long. South American arapaima can grow to be 10 feet long and weigh over pounds.

The slow-moving fish have little to fear from the piranhas who share their habitats. Piranha teeth measure up to 4 millimeters long. The upper and lower teeth interlock , allowing the piranha to slice through vegetation, meat, bone, and even metal.

For that reason, piranhas shed the teeth on one side of their head—both lower and upper jaws— at once. A study in Evolution and Development found that piranhas grow a new set of teeth in their jaws and then swap out the old teeth for the new set several times during their lives.

During his travels in the Amazon, TR heard tales of the piranha's vicious nature and recounted them in his book Through the Brazilian Wilderness. But as scientists now know, this characterization is false. Piranha , a cult classic directed by Joe Dante, rode the wave of this trend.