Komodo dragons have venomous bite

Komodos grow to two metres in length

The Komodo dragon has a bite tinged with a deadly venom, according to researchers.

Previously it was thought the Komodo's mouth harboured virulent bacteria that quickly infected and subdued prey.

But an analysis of Komodo specimens has shown a well-developed venom gland with ducts that lead to their large teeth.

The Proceedings of the National Academy of Sciences report shows that rather than using a strong bite force, Komodos keep a vice-like grip on their prey.

In this way, the venom can seep into the large wounds they make with their teeth.

The work is a follow-up to a 2006 study by Bryan Fry of the Australian Venom Research Unit at the University of Melbourne.

The study showed that known venomous lizards, such as the Gila monster of the south-western US, were in the same lineage as Komodo dragons.

It went on to describe how the venom systems in the lizards and snakes actually came from a common ancestor.

Members of the same team have now used a computer simulation to model the skulls of Komodo dragons. They found that their bite was only one-sixth as strong as that of the Australian saltwater crocodile, which has a similarly-sized skull.

Instead, Komodo skulls seem optimised to withstand stress along their length - that is, to resist prey that is pulling away.

Further, the team took MRI scans of Komodo heads, identifying a large venom gland and ducts that lead to spaces between the animals' teeth.

Dissection of the duct showed toxins that are known to lower blood pressure and act as anti-coagulants - causing prey to go into shock and bleed to death.

'Radical' suggestion

Megalania may have been the largest venomous animal in history

The researchers suggest that Komodo dragons produce a small amount of comparatively weak venom, and the delivery method is not the most efficient.

"These lizards make a huge wound using their teeth; that's good enough to get the venom in," says Christofer Clemente, a comparative physiologist at the University of Cambridge and a co-author of the study.

"They are robust enough that they can hang on to prey. Other groups like snakes are much more fragile - they have to bite something and let it go. So they have these hollow fangs and more deadly venom."

The findings would put another leading theory for Komodo predation to rest: that bacteria present in their mouths quickly infect prey.

That suggestion was first posited briefly in a seminal book by Walter Auffenberg in 1981. However, more recent experiments have failed to show a bacterium species common to all Komodos.

"That whole theory has been touted around for years, but has never really been proven," said Ian Stephen, curator of herpetology at the London Zoo.

Dr Stephen told the BBC that the suggestion of the venomous nature of Komodo dragons was a "radical" one that raises the question of why the venom gland had not been discovered in dissected specimens before now.

But, he said of the paper, "it is very interesting and it does all seem to make sense".

The results also suggest that the now-extinct Megalania - a close relative of Komodos that grew to seven metres in length - would also have been venomous. It would therefore have been the largest venomous animal ever to have lived.