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Komodo Dragon Found to be Venomous

Thursday 21st May 2009

Komodo dragons feeding on a buffalo carcass

Following research into the Komodo dragon’s feeding behaviour, scientists have made the exciting discovery that the world’s largest lizard is venomous. The report, published in Proceedings of the National Academy of Sciences, shows that the gigantic monitor lizard possesses complex venom glands in its jaw, which excrete a variety of toxic substances that prevent blood clotting and lower blood pressure in its prey. In contrast to the elaborate venom injection system used by snakes, the Komodo dragon’s venom is administered relatively crudely, seeping into the large wounds made by the teeth. This means that even if the injured animal escapes, it will rapidly succumb to shock and blood loss induced by the venom.

The study also helps to shed light on why such a large, powerful carnivore would require venom in order to help bring down prey. Through analysis of the structure and mechanics of the skull and jaw muscles, it was discovered that bite force of the Komodo dragon is not particularly strong. Rather than inflicting devastating bites, the jaws are best suited for clamping on to prey and resisting it from pulling away, giving time for the venom to penetrate the wound. This means that less effort is required to subdue its victim, and allows larger animals to be preyed upon.

The findings challenge the commonly accepted theory that toxic bacteria found in the Komodo dragon’s mouth help to take down prey by infecting bite wounds, leading to fatal blood poisoning. While a previous study has demonstrated that Komodo dragon saliva does contain a variety of toxic bacteria, no single disease-causing strain was found to be consistently present in all individuals sampled. In addition, all of the bacteria species were generally similar to those found in the mouths of other reptiles or in the guts of mammals on which the Komodo dragon preys.

It was previously thought that only two lizard species, the Gila monster (Heloderma suspectum) and the beaded lizard (Heloderma horridum) were venomous. However, a study by the same team of researchers published in 2006, showed that other lizard species such as the lace monitor (Varanus varius) and the bearded dragon (Pogona barbata) may also possess mild venom.

Further information

To find out more about the study see:

Fry, B.G. et al. (2009) A central role for venom in predation by Varanus komodoensis (Komodo Dragon) and the extinct giant Varanus (Megalania) priscus. Proceedings of the National Academy of Sciences, In Press. Available at:
www.pnas.org/cgi/doi/10.1073/pnas.0810883106

Both mammals and lizards have several representatives which, in surprising contrast to the rest of the group, are venomous. See below for some of those found on ARKive:

Gila monster (Heloderma suspectum)

The venomous bite of the Gila monster is used as a defensive measure rather than to attack prey. If threatened, these lizards will back away hissing with their mouth open, and if provoked they attack surprisingly quickly. The bite can be extremely painful to humans, but is rarely life-threatening.

Water shrew (Neomys fodiens)

Water shrews have voracious appetites and must eat about half their own body weight in food every 24 hours to stay alive. Unusually amongst mammals, they possess venomous saliva, which aids in stunning prey.

Bengal loris (Nycticebus bengalensis)

One of the more curious aspects of loris biology is the production of a toxic substance from glands on the insides of the elbows. This toxin, secreted in sweat, is licked off the gland and mixed with saliva (activating the toxin) where it appears to be channelled up the fine comb-like teeth at the front of the mouth. When defending itself, the Bengal loris' bite transmits this poison, and people who have been bitten have reported it to be particularly painful, with anaphylactic shock occurring in some cases.

Platypus (Ornithorhynchus anatinus)

In male platypuses, the rear ankles are equipped with a horny spur connected by a duct to a venom gland, which is used to inflict wounds on predators and other males.

Visit MyARKive to view a selection of images and videos in the Surprisingly Venomous Species scrapbook.

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