Vipers, colubrids and alpids have different ways of behaving, and these have been revealed in great detail for the first time.
Few acts in nature inspire more fear and curiosity than snake bites. Venomous reptiles must move quickly to sink their teeth into their prey before it can escape—in rodents, this can happen in as little as 60 milliseconds. Until recently, videography technology did not allow for the capture of these deadly maneuvers in high quality; recent improvements have made it possible, so Alistair Evans and Silke Clauren of Monash University, Australia, decided to study how snakes from the families Viperidae, Elapidae, and Colubridae sink their teeth into their prey. In a study published inJournal of Experimental Biology Researchers reveal: Vipers bar their teeth and then move them to an optimal position before injecting venom; Elpids “squeeze” venom through repeated bites; and Colubrids move their jaws from side to side to tear a cut and inject maximum venom.
Instead of staying in Australia to uncover the intricacies of the bite, Klorane traveled to the outskirts of Paris, France, to Venomworld, where Remi Casas milks venom from some of the world’s most dangerous snakes for medical and pharmaceutical purposes. There, together with Anthony Herrell of the Muséum national d’Histoire naturelle CNRS , Casas challenged 36 species of snakes—from the western rattlesnake (Crotalus atrox) and the West African carpet viper (Echis ocellatus) to the spiny-scaly adder (Acanthophis rugosus)—to leap into a warm, muscle-like cylinder of medical gel that simulates a small animal. The encounters were recorded with two cameras at 1,000 frames per second and the lightning-fast maneuvers were recreated in 3D. Kloren recalls that stun- ning a venomous snake with a gel ball on a stick was an adrenaline-pumping experience—“I jumped a few times,” she admits—but it was worth it for the amazing footage.
One hundred hops
After filming more than 100 snake leaps in minute detail, the team found that vipers sink their teeth into simulated prey within 100 milliseconds of the leap—with the blunt-nosed viper (Macrovipera lebetina) accelerating to 710 m/s² and sinking its teeth within 22 milliseconds; elphidian snakes bit (stung) at a similar speed to vipers. In addition, vipers moved fastest when leaping. Bothrops asper, sometimes called the “ultimate pit viper,” reached speeds of more than 4.5 m/s after accelerating from over 370 m/s², while the fastest elphidian—the spiny-scaly adder—reached “only” 2.5 m/s.
Focusing on the vipers’ teeth, the researchers saw the sharp “teeth” embedded in the simulated prey, but if the viper was “not happy” with the tooth’s placement, it pulled it out and reinserted it at a better angle—in effect, moving the tooth forward. Only after the teeth were firmly in place did the vipers close their jaws and inject venom. In contrast, alpids such as the South African coral cobra (Aspidelaps lubricus) and the forest cobra (Naja melanoleuca) adopted a more cunning strategy: crawling to the prey before lunging and repeatedly biting, while the jaw muscles tensed to “squeeze” the venom in. Meanwhile, the two colubris—whose teeth are located further back in the mouth—pounced from greater distances, gripped the prey with their jaws around it, and moved their jaws from side to side to tear a crescent-shaped incision and inject a maximum dose of venom. In one case, a blunt-nosed viper misjudged the distance, hitting and breaking a right tooth; the team believes such cases are more common than previously thought, as teeth are sometimes found in snake feces after being swallowed.
Venomous snakes use very different strategies to deliver a lethal bite: vipers and alpids strike elegantly before the victim is even aware of their presence, while colubrid bites inflict maximum damage.
for the scientific article inJournal of Experimental Biology
