Few actions in nature inspire more fear and fascination than snake bites. And the venomous reptiles have to move fast to sink their fangs into their prey before their victim flinches, which may be as little as 60 ms when hunting rodents. Until recently, video technology was not sufficiently sophisticated to capture the deathly manoeuvres in high definition, but recent improvements have made this possible, so Alistair Evans and Silke Cleuren from Monash University, Australia, decided to get to the heart of how venomous viper, elapid and colubrid snakes sink their fangs into their dinner. Publishing their research in Journal of Experimental Biology , the researchers reveal how vipers sink their fangs into their victims before walking them into position to inject venom. Elapids squeeze venom into their victims by biting repeatedly. And colubrids sweep their jaws from side to side to tear a gash in their victim and deliver maximum venom.
But instead of staying in Australia, to reveal the fine detail of how each family of snakes bites, Cleuren travelled to the outskirts of Paris, France, home of Venomworld, where, Remi Ksas collects venom from some of the world's most dangerous snakes for medical and pharmaceutical uses. There, Cleuren, Anthony Herrel (Museum national d'Histoire naturelle CNRS, France) and Ksas tempted 36 species of snake – from western diamondback rattlesnakes (Crotalus atrox) and west African carpet vipers (Echis ocellatus) to the rough-scaled death adder (Acanthophis rugosus) – to lunge at a cylinder of warm muscle-like medical gel resembling a small animal, recording the encounters with two cameras at 1000 frames/s to recreate the lightning-fast manoeuvres in 3D. Cleuren recalls that annoying a venomous snake with a piece of gel attached to a stick was an incredible adrenaline rush, 'I flinched a couple of times', she admits, but adds that it was worthwhile to get the amazing footage.
After capturing more than 100 snake strikes in minute detail, the team saw the vipers embed their fangs in the fake prey within 100ms of launching a smooth strike – with the blunt-nosed viper (Macrovipera lebetina) accelerating up to 710m/s2 and landing its bite within 22ms; the elapid snakes bit their victims as quickly as vipers. In addition, the vipers moved the fastest as they struck, with Bothrops asper – sometimes known as the ultimate pit-viper – reaching speeds of over 4.5m/s after hitting accelerations of more than 370m/s2, although the fastest elapid – the rough-scaled death adder – only reached speeds of 2.5m/s.
Focusing on the vipers' fangs, the team saw the needle-like teeth sink into the fake prey, but if the viper wasn't happy with the position of a fang, it pulled it out to reinsert it at a better angle, effectively walking the fang forward. Only when the fangs were comfortably in place did the vipers close their jaws and inject venom into their catch. In contrast, the elapid snakes, such as the Cape coral cobra (Aspidelaps lubricus) and the forest cobra (Naja melanoleuca), used a stealthier strategy, creeping closer to their victim before lunging and biting repeatedly as their jaw muscles tensed to squeeze the venom into their dinner. Meanwhile, the two colubrid snakes, with fangs further back in their mouths, lunged over the greatest distances before clamping their jaws around their meal, sweeping their jaws from side-to-side to tear a crescent-shaped gash in the victim to deliver the maximum dose of venom. And on one occasion, a blunt-nosed viper misjudged the distance to its prey, hitting the right fang and breaking it off. But the team suspects that this occurs more than you'd think, with fangs turning up in snake scats after being swallowed.
Venomous snakes use dramatically different strategies to deliver their deadly bites. Vipers and elapids strike elegantly before victims are even aware of their presence and colubrid bites inflict the maximum damage. These creatures don't pull any punches when they mean business.
