Archives of The Cold Blooded News

The Newsletter of the Colorado Herpetological Society

Volume 31, Number 7;   July, 2004

The Deadly Secret of 'Harmless' Snakes

by John Veld

This discovery, which is likely to send shivers of concern through the pet trade, was made by Bryan Fry, deputy director of the Australian venom research unit at the University of Melbourne, while on an evolutionary hunt for the first venomous snake.

Fry's discovery has shaken the foundations of current theory on reptile evolution and opened the door for a new class of drugs. And, because many snakes assumed to be harmless are sold in pet shops around the world, experts have started re-evaluating the relative danger of supposedly non-venomous snakes.

Fry, fascinated by venomous snakes and venom evolution, and whose findings have appeared in three scientific journals in recent months, has won R1.2 million grant from the Australian Research Council to continue his work. He set off last year on a worldwide adventure to track down when and in what snake species venom first evolved. The result was the discovery that venom developed only once during snake evolution, about 60 million years ago. This is millions of years earlier than previously thought, and before the snakes now commonly [considered] non-venomous even arrived on the scene.

"Contrary to popular belief, venom appears to have evolved at about the same time as advanced snakes started to appear. Even fangs and large venom glands arrived much later," Fry explained. "This means the first venomous snakes evolved from the heavy-bodied swamp monsters similar to the anacondas." Anacondas are the huge tropical forest snakes from South America, similar to African pythons but even bigger.

"These snakes traded in their heavy muscle for speed and agility, and venom rather than muscle became the tool necessary for these snakes to capture their prey," Fry said. The consequence was that venom was an inherent condition of virtually all advanced snakes, including the assumed non-venomous species, he explained. Fry has now analyzed the venoms from the many different snake lineages collected from his worldwide hunt and elsewhere, some of which were common pet-store snakes. He discovered that their venoms were just as complex as. those of some of the world's deadliest snakes, such as cobras, puff adders, and taipans.

"Some non-venomous snakes have been previously thought to have only mild 'toxic saliva', but these results suggest that they possess true venoms," Fry said. "We even isolated from a rat snake - a snake common in pet stores - a typical cobra-style neurotoxin, one that is as potent as comparative toxins found in close relatives of the cobra. But not all of these snakes are dangerous. It does mean, however, that we need to re-evaluate the relative danger of non-venomous snakes."