How snake bites really work
A venomous snake bite is not something you want to encounter while hiking or camping. For brave scientists who study snakes – that is, herpetologists – the mechanics behind the reptiles’ fast-moving fangs are more fascinating than frightening. Snakes must move incredibly quickly to sink their fangs into their prey before the prey jumps. When hunting rodents, this can last as little as 60 milliseconds.
Thanks to advances in video technology, a group from Monash University in Australia is observing up close and personal how venomous vipers, elapids and colubrids flex their fangs. In their study published today in the Journal of Experimental Biologythe team describes the differences between biting tactics in these different types of snakes.
Finding snakes in… France?
Despite working in one of the world’s snake hotspots, study co-authors Alistair Evans and Silke Cleuren traveled from Australia to Venomworld, near Paris. At Venomworld, herpetologist Remi Ksas collects venom from some of the world’s most dangerous snakes for medical and pharmaceutical purposes.
Cleuren, Ksas and Anthony Herrel of France’s National Museum of Natural History studied 36 species of snakes, including western diamondback rattlesnakes (Crotalus atrox), West African carpet vipers (Echis ocellatus), and the large-scale death adder (Acanthophis rugosus). They tempted the snakes to lunge at a muscle-like cylinder of hot medical gel resembling a small animal.
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They used two cameras running at 1,000 frames per second to record the encounters, to recreate the snakes’ lightning-fast maneuvers in 3D. Cleuren remembers that she “flinched a few times,” but the adrenaline rush was worth it to film the footage. They ended up capturing over 100 snake shots in great detail.
They discovered that venomous snakes use radically different strategies to deliver their deadly bites. Vipers and elapids strike more elegantly before their victims are even aware of their presence, while colubrid bites inflict maximum damage.
Vipers: The demons of speed
A viper (Deinagkistrodon acutus) hitting a cylinder of medical gel. The movie plays at 3 percent speed. CREDIT: Silke Cleuren
When a viper strikes, it sinks its fangs into its victim’s skin before moving it into a position where it can inject its deadly venom. They insert their fangs into their prey within 100 milliseconds of launching a strike.
The blunt-nosed viper (Macrovipera lebetina) can accelerate up to 710 meters per second squared, or about 1,588 miles per hour in one second. It will also bite in 22 milliseconds.
The vipers in the study also moved the fastest when they struck. Bothrops asper– or the ultimate pit viper – reaches speeds of over 4.5 meters per second after achieving accelerations of over 370 meters per second squared.
Focusing on the vipers’ fangs, the team watched as their needle-like teeth dug into the false prey. However, if the viper was unhappy with the position of a fang, it would remove it and reinsert it at a better angle. Vipers closed their jaws to inject venom only when their fangs were comfortably in place.
Elapids: Masters of Stealth
An elapid snake (Aspidelaps lubricus) hitting a cylinder of medical gel. The movie plays at 3 percent speed. CREDIT: Silke Cleuren
The elapid snakes in their studies bit their victims as quickly as vipers. However, the fastest elapid – the coarse-scaled death viper – only reached speeds of 2.5 meters per second.
They deployed a different strategy of working the venom into their victims by biting them repeatedly. The Cape coral cobra (Alubricus spidelaps) and the forest cobra (Naja melanoleuca), act more stealthily. They approach their victim before lunging and biting them several times. As they bit, their jaw muscles tensed to squeeze the venom into their meal.
Colubrids: biters with saw-shaped jaws
A colubrid snake (Toxicodryas pulverulenta) hitting a cylinder of medical gel. The movie plays at 30 percent speed. CREDIT: Silke Cleuren.
A colubrid snake (Toxicodryas pulverulenta) hitting a cylinder of medical gel. The movie plays at 30 percent speed. CREDIT: Silke Cleuren.
Both colubrid snakes in the study had fangs further back in their mouths. They would rush the greatest distances before locking their jaws around a meal. Once in place, they swept their jaws from side to side to tear a crescent-shaped gash in the victim. Once the cut was in place, they delivered the maximum dose of venom.
Snakes, they are like us
On one occasion, a blunt-nosed viper misjudged the distance to its prey. The result? His right fang was broken.
According to the team, this type of fang breakage probably happens quite often. Fangs tend to appear in snake droppings after being swallowed.
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