Venomous snakes inhabit a world of perceptions different from our own. “Before mammals have a chance to spot it and start moving, they are already on top of it,” said zoologist Alastair Evans from Monash University (Australia).
This is because in the race of reflexes, the snake usually wins. For a mouse or human, it takes less than half a second to register a threat and respond. But venomous snakes are able to pounce and bite their prey in a fraction of that time.
It is so fast that it was difficult to even visualize the process. Evans and his colleagues decided to use high-speed video cameras to record and reconstruct the fast and complex movements of 36 species of venomous snakes.
The result, described in a study published last month in the Journal of Experimental Biology, is a glimpse into the different methods these creatures use to sink their fangs into their victims.
To conduct the experiment, Evans needed snakes. He then turned to biologist Anthony Herrell, of the National Museum of Natural History in Paris, who is collaborating on the research with VenomWorld, a French company that produces the venom used in manufacturing antivenoms.
Herrell photographed the snakes at a rate of 1,000 frames per second with the VenomWorld team and Silke Clorine, then a graduate student at Monash. Working under strict security protocols, they attached a cylinder of ballistic gel (heated to mimic the body temperature of mammals) to the end of a long stick. Then they presented it to snakes from three families.
Animals made mistakes often. However, when his attacks were successful, the results were impressive.
Snakes, one group studied, are ambush predators. They curl up in one place and wait, with their large prey retreating. When prey approaches, they explode in activity, darting their heads smoothly and quickly.
In one video, a snake, in tens of milliseconds, “opens its mouth and unleashes its fangs,” Herrell said. After injecting its venom, the snake released the cylinder.
In nature, this bite-and-release technique allows the snake to deliver its venom and then retreat if the victim resists. Even if the prey escapes, the poison will eventually kill it. Then, using its tongue to trace the stricken animal, the snake can feed in peace.
Researchers have also observed that pit vipers modify their bites after contact. They removed prey one at a time, moving their teeth forward so they could insert it better and deeper.
According to Herrell, this information can contribute to the design of protective clothing. But he stressed that if left alone, most snakes “are not that dangerous.”
In one video, a snake broke its right fang after coming into contact with the gel, sending the tooth flying into the air. “This has never been captured on film before,” Evans said. (Don’t worry, snakes routinely replace their prey.)
The second family of snakes tested was the Elapids, a group that includes cobras, mambas and taipans. The four species the team studied tended to approach their prey, attack more slowly than many pit vipers, and snap their jaws more frequently. Each time the jaw muscles contract, the venom is forced into the fangs to be injected into the prey.
Finally, there were the colubrids, only a few of which pose a venomous threat to humans. The researchers examined two species whose fangs were positioned at the back of the mouth, unlike fossil vipers and eilipids. Upon contact with the gel, the snakes drag their teeth over it, tearing apart their potential victim until the venom released from these rear fangs flows into the open wounds.
Biologist Jessica L. said: “It’s an impressive data set, because animals don’t do what you want them to do,” said Tingle of Brown University, who was not involved in the research. “This contributes to our understanding of how attack works, in part because variation is at the heart of much of biology.”
Tingle’s only criticism is that most of the snakes were pit vipers. “I think we need to be careful about generalizing the results” to groups like pythons and boas, she said. The study examined a small number of snake species, which represent half of all snake species.
Herrell found the different behaviors of snakes fascinating. “We thought these attacks were very formulaic, like a little bot that always does the same thing.”
The videos he and his colleagues collected revealed the opposite. “These animals are much more flexible. They can do a lot more than most people think,” Herrell said.
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