Stingrays are placid fish whose larger species are occasionally known to tolerate the efforts of gung-ho scuba divers to “hitch a ride” by clinging to their fins.
But when the usually non-aggressive creatures feel threatened or are trodden on, they are capable of delivering horrific, agonising injuries by lashing out with the razor-sharp, barbed sting at the end of their tails.
The barbs, which grow out of the bayonet-like sting like fingernails, are designed to snag in the flesh of the ray’s unwary victim. Each barb is serrated and can be up to 20cm (8ins) long, and is coated with a paralysing toxin which the ray secretes along two grooves in its tail.
Stingray injuries are common, as the fish are often found around the coastline where people swim and paddle. Most wounds are sustained to the legs or feet when stingrays are trodden on in the shallows. In some cases the stingray’s toxic barb is broken off and remains in the wound, especially when the fish is pulled off the victim.
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Fatal attacks, such as the one which today cost the life of Australia’s “Crocodile Hunter” Steve Irwin, are however almost unheard of.
It is only when the barb enters the body through the chest area, so that the heart or other vital organs are damaged and the poison is administered directly, causing the blood vessels to constrict, that very serious injuries can occur and death is more likely.
Dr Bryan Fry, deputy director of the Australian Venom Research Unit at the University of Melbourne, said today that a dose of stingray venom was “extraordinarily painful”.
“If (Irwin) was conscious he would have been in agony,” Dr Fry told the Reuters news agency.
Dr Fry said stingray venom was a defensive weapon similar to that in stonefish, whose poison is generally fatal, but in the stingray’s case the toxin was not lethal. It was the serrated barbs on the stingray’s tail that would have delivered the fatal injury, he said.
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“It’s not the going in, it’s the coming out,” Fry said. “They have these deep serrations which tear and render the flesh as it comes out.”
Dr Geoff Isbister, a clinical toxicologist, said that little was known about stingray venom, but he agreed that it was the physical trauma associated with the wound that would have killed Irwin.
“What happened to Steve Irwin is like being stabbed in the heart,” Dr Isbister said.
“The majority of stingray injuries in Australia result from people stepping on them in shallow water and getting a stingray barb in the ankle.”
Victoria Brims, a shark and stingray expert, has said that Irwin’s death was only the third known stingray death in Australian waters. An Aboriginal boy died several years ago, while the previous record death was in Melbourne in 1945. Only 17 such deaths have ever been recorded worldwide.
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“It seems he was incredibly unlucky to die,” said Bernard Lagan, Times correspondent in Sydney.
Stingrays are members of The Dasyatidae family of cartilaginous fish. There are at least 70 different species, found scattered around the world’s oceans and also in freshwater lakes in South America. They are most common in tropical waters such as the area around the Great Barrier Reef in Australia, where Irwin was attacked.
The largest species can grow to more than 7ft (2m) in width and their tails can be twice as long as their bodies. They like to lie half-buried in the sand or mud around coasts, eating small molluscs and crustaceans on the sea floor. The animal has a reflexive defence mechanism causing it to strike the victim with its tail.
Sean Connell, a marine ecologist, said that stingrays are related to sharks and use their long, barbed tails to protect themselves from predators, such as sharks and killer whales. He hinted that Irwin and his cameraman may have made the ray feel threatened.
“I have never heard of an unprovoked attack from a stingray,” Connell said. “Such attacks usually only happen when the ray is under severe stress.”