The truth about piranha attacks
Serrasalmus rhombeus is one of the most aggressive piranhas.
Piranhas aren't the man-eaters folklore would suggest; you're much more likely to lose a toe, according to the results of a new survey of piranha attacks in Suriname.Humans are much more likely to be bitten when piranhas are removed from the water when fishing than they are while bathing in the water, the study claims.
"Many human deaths attributed to piranhas are probably cases of scavenging on drowned or otherwise already dead persons", says Jan Mol of the University of Suriname, who has just published the results of a study on human attacks by piranha.
"In 15 years of field work in Suriname, often wading for hours through 'piranha-infested' streams and catching piranhas with hook and line while bathing in the river, I was never injured by free-swimming piranhas.
"Piranhas are usually more dangerous out of the water than in it and most bites occur on shore or in boats when removing a piranha from a gillnet or hook, or when a 'loose' piranha is flopping about and snapping its jaws."
Other studies have come to similar conclusions, but Mol suggests that under some situations the risk of piranha attack is very real.
"In the low-water season, when hungry fishes become concentrated in pools, some piranha species may be dangerous to any animal or human that enters the water."
Serrasalmus rhombeus
Mol studied Serrasalmus rhombeus attacks at three locations in Suriname; the villages of Donderkamp and Corneiskondre on the Wayombo River and a recreation park at Overbridge on the Suriname River.Dozens of people had been attacked at each location, with most injuries resulting in bites to the heel, soles of the feet and toes.
More serious deeper wounds were also inflicted to the legs, arms and body. Some bites were so severe that the fish completely removed the toes, including the phalange bone.
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Reader Mike Rizzo suffered this bite from his rhombeus last year. Full story �
The recovery of toe phalanges, complete with human flesh and bits of toenail, identified the culprits as Serrasalmus rhombeus, one of the largest and most aggressive piranhas.
"Individuals of this species tend to remain several weeks at one site and this may explain why the respective piranhas were caught at exactly the same spot after their attacks on bathers", says Mol.
"Also, characteristics of wounds of victims from Overbridge resembled bite marks previously documented as caused by S. rhombeus. Furthermore, no Surinamese freshwater fish other than a piranha could be responsible for the injuries reported here."
None of the three locations surveyed had reported any human deaths due to piranha attacks.
Two epileptic bathers whose badly mutilated bodies were retrieved from the water are believed to have suffered seizures and then been scavenged by the fish.
Villagers interviewed by Mol claimed that piranha attacks in the small villages were unheard of until the population of the village began to rise in 1990.
When the human population peaked, the number of piranha attacks increased.
Feeding, not defence
While piranha attacks in other areas have been attributed to attacks by breeding piranhas defending their eggs and fry, Mol believes this is not the case in Suriname."In Surinamese rivers most of the reproductive activity of S. rhombeus occurred in the long rainy season of April to July, while most piranha attacks in Overbridge and Donderkamp occurred during the low-water (dry) season of September to November.
"Nevertheless, there is a small possibility that some individual piranhas were reproducing and guarding their spawn and/or spawning sites out of the main season."
The sites not only lacked stereotypical spawning sites for the species, but the surveys revealed only sexually immature juvenile piranhas, so Mol believes that the attacks stem from feeding behaviour, not the defence of offspring.
How to avoid being eaten
1. Piranhas are only found in certain rivers in the Amazon basin. Avoid swimming in South America, unless you have to. If you must bathe there, fill a bucket and wash on land. But look out for Centromochus!2. Piranha attacks are greatest during the dry season when water levels are lowest and the fish breed, resulting in thousands of hungry young piranhas in the water.
3. Human attacks are most common in areas where human densities are highest in the water, such as popular swimming spots.
4. Noise and splashing attracts piranhas, so try to avoid making a commotion while you're taking a dip. Piranha most commonly attack children for this reason.
5. If you're a menstruating woman, don't swim in the water, as any leaking blood may attract piranhas. In Amerindian villages, women in menstruation are not allowed to bathe for this reason, says Mol.
6. Don't throw dead fish, offal or other food into the water. Piranhas are not strictly carnivorous, so any food in the water might attract them into the area.
7. Piranha attacks are not isolated incidents. If you spot any signs erected by locals saying "Warning Piranhas", it's probably sensible to avoid bathing there.
For more information see the paper: Mol JH (2006) - Attacks on humans by the piranha Serrasalmus rhombeus in Suriname. Studies on Neotropical Fauna and Environment, December 2006; 41(3): 189-195.
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Matt Clarke: 8.1.2007Views: Read 40,429 times
Comments feed
Reader comment
Date: Monday July 2nd, 2007, 12:54 pm
"Wow, how long has it taken for this to hit the mainstream?:http://news.bbc.co.uk/1/hi/s..."
Posted by: Jason Collins-webb - 2 years, 4 months agoDate: Monday July 2nd, 2007, 12:54 pm
Reader comment
Date: Wednesday September 5th, 2007, 1:15 am
"Here in northeast Brazil, when they are spawning among egeria densa and other aquatic plants in shallow water, it is common for the spotted piranha to give warning nips to bathers who come too close.
Usually one bite is enough to send anyone away because it usually causes a deep cut and draws blood.
Sometimes two or three people get bitten almost simultaneously and this scares the tourists, but the locals know that it won't get more serious than this. This occurs primarily in the lakes formed by dams on the São Francisco river.
"
Date: Wednesday September 5th, 2007, 1:15 am
Reader comment
Date: Friday January 11th, 2008, 1:20 am
"A gentleman I met in the upper Purus had two largish "holes" (about 5 cm wide, 1 cm deep) in his lower leg. Wading across a shallow part of the river, he was bitten by two piranhas, one of which he managed to catch with his hands, then take home and grill for dinner. There are some tough buggers out there."
Posted by: Simon Hamilton - 1 year, 10 months agoDate: Friday January 11th, 2008, 1:20 am
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 | Editor-in-Chief, Matt Clarke, writes the regular Interesting Imports column on rare and unusual fish in the UK aquarium trade. He's kept fish for 30 years and holds a degree, two higher degrees and two diplomas in fish biology, taxonomy and computational biology. |
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"The reputation of the piranha being a "man eater" was spawned by a trip to Brazil in the early part of last century, of the US president Teddy Roosevelt.
Posted by: Bill Bradbury - 2 years, 9 months agoIn order to impress the celebrity, the Brazilians contrived a showy demonstration on the Amazon, or one of it's tributaries. They dammed part of the river then set about catching piranha ( the species is not recorded as far as I know). The fish were put into the dammed section of the river until it was teeming with them. Obviously, this was indeed an unnatural environmennt, so the fish behaved unnaturally. They were starved for weeks, until Roosevelt and his entourage of reporters appeared. The Brazilians then drove a cow into the water, having first slit its udder allowing blood to flow freely. The starving piranha attacked en masse, reducing the poor bovine to a skeleton. With all the news reporters on hand, the story soon appeared in the major papers in the US!
This is a true account that can be checked out."
Date: Thursday February 1st, 2007, 2:07 pm