Trilobites Lights, Camera, Venom: What Happens When a Snake Strikes
High-speed video helped researchers to get close-ups of the attack strategies of three snake families.
Slow-motion videos of strikes by a mangrove snake, a puff adder, a blunt-nosed viper, a Cape coral snake and a Chinese moccasin.
Venomous snakes inhabit a different perceptual world than we do. “Before the mammal has even had a chance to detect them and start moving, they’re on top of you,” said Alistair Evans, a zoologist at Monash University in Australia.
That’s because in a race of reflexes, the snake usually wins. For a mouse or human, it takes less than half a second to register a threat and react. But venomous snakes are capable of launching themselves at and biting their prey in a small fraction of that time. “It’s ridiculously fast,” Dr. Evans said.
So fast that it’s been challenging to even visualize. But in a study published Thursday in the Journal of Experimental Biology, Dr. Evans and his colleagues used high-speed video cameras to record and reconstruct the complex, rapid movements of 36 species of venomous snakes.
The result is a harrowing glimpse of the different approaches that these creatures take to sink their fangs into their victims.
To do this work, Dr. Evans needed snakes. So he reached out to Anthony Herrel, an evolutionary biologist at the National Museum of Natural History in Paris who collaborates on research with VenomWorld, a French company that produces venom used to make antivenoms.
Dr. Herrel filmed the snakes at 1,000 frames per second alongside VenomWorld staff and Silke Cleuren, then a Monash graduate student. Operating under strict safety protocols, they placed a cylinder of ballistic gel (warmed to mimic mammalian body temperature) on the end of a long pole. They then presented it to snakes from three families.
The animals missed often. But when their attacks were successful, the results were — striking.
Vipers, one of the groups they studied, are ambush predators. They sit coiled in one place and wait, their large fangs tucked away. When prey moves close, they explode to life, accelerating their heads smoothly and quickly.
In one of the videos featuring the sharp-nosed viper, within tens of milliseconds, “it’s opening its mouth and boom, the fangs are inserted,” Dr. Herrel said. After injecting its venom, the snake released the cylinder.
In the wild, this bite-and-release technique allows a snake to administer its venom and then back off in case the victim retaliates. Even if the prey flees, the venom will ultimately kill it. Then, using its tongue to follow the trail of the doomed animal, the snake can feed in peace.
The researchers also observed vipers adjusting their bites once they had made contact. They removed one fang at a time, walking the teeth forward until they achieved a better, deeper insertion.
Dr. Herrel said this could inform the design of protective clothing. But he also pointed out that if most snakes are simply left alone, “they’re actually not that dangerous.”
In one of the videos, a blunt-nosed viper snapped off its right fang after making contact with the gel, sending the tooth spiraling through the air. “That’s never been caught on film before,” Dr. Evans said. (Not to worry — snakes routinely replace their fangs.)
A second family of snakes to be tested were the elapids, a group that includes cobras, mambas and taipans. The four types the team studied tended to creep closer to their prey, strike more slowly than many of the vipers and squeeze their jaws over and over again. Each time the jaw muscles contracted, venom was pushed into the fangs to be pumped into the prey.
Finally, there were the colubrids, of which only a handful pose a venomous threat to humans. The researchers examined two types whose fangs, unlike those of vipers and elapids, were positioned in the back of the mouth. After connecting with the gel, these snakes raked their teeth across it, lacerating their would-be victim so the venom dispensed from those rear fangs could flow into open wounds.
“It’s a really impressive data set because animals notoriously don’t do what you want them to do,” said Jessica L. Tingle, an integrative organismal biologist at Brown University who was not involved in the research. “That really adds to our understanding of how striking works in part because variation is at the heart of a lot of biology.”
Dr. Tingle’s only critique is that most of the snakes were vipers. “I think we need to be cautious about generalizing the results” to groups like the pythons and boas, she concluded. The study also examined few colubrids, which represent half of all snake species.
Dr. Herrel also found the different snake behaviors notable. “We used to think these strikes are very stereotyped,” he said, “like a little robot always doing the same thing.”
The videos that he and his colleagues collected revealed the opposite.
“These animals are much more flexible,” Dr. Herrel said. “They can do so much more than most people think.”