Reptile venom acts like ketchup in a bottle after shaking.
The normally thick and viscous venom flows easily once it is is in motion, much like ketchup after being shook. Both venom and ketchup are non-Newtonian fluids, meaning they stay viscous until they start flowing, according to a study published in Physical Review Letters.
Like that ketchup bottle that won’t stop once it gets going, the venom too moves more freely the faster it is moving. Except instead of with a ketchup-splattered hot dog, the snake ends up with a dead mouse.
Once the deadly substance is in motion, surface tension helps it continue along its path into the intended victim’s flesh. The stickiness of the venom helps it stay together and move from fang to prey. Similar physical forces cause water to rise slightly up a straw or form a meniscus in a full cup.
The interaction of the fangs and flesh of the bitten animal form a channel along which the venom flows. The flesh acts like blotter paper to wick the venom in. The suction created by the blotting effect helps the venom keep flowing. The wicking of venom into flesh also means that the snake doesn’t need to expend energy to pump the venom in.
J. Leo von Hemmen, a biophysicist at the Technical University of Munich, Germany and Bruce Young, a biologist at the University of Massachusetts in Lowell, started their research after noticing that only a seventh of venomous snakes, such as rattlesnakes, have hypodermic needle-like fangs.
Many venomous snakes and lizards have much simpler set-ups, often only grooves in the fangs, and yet are effective hunters. The fangs of the mangrove snake and banded snake were both examined by the researchers to understand how venom flows.
The physical properties of the venom itself allow venom to get past even bird feathers, which usually deflect liquid. Snakes that regularly eat birds were found to have deeper channels in their fangs, which increased the ability of the venom to evade feathers.
As the snake waits for its prey, the venom stays put because it is a non-Newtonian fluid. That’s one reason why snakes and Gila monsters aren’t constantly dribbling venom. But once the snake makes its lighting quick strike the venom becomes a deadly squirt.
Keep that image in your head at the next summer barbecue.
IMAGE 1: A Gaboon viper, Bitis gabonica, showing its fangs, the largest of any snake. (Wikimedia Commons).
IMAGE 2: The mangrove snake, Boiga dendrophila (WIkimedia Commons).
IMAGE 2: Scanning electron micrographs showing the prominent grooves (horizontal arrows) on the fangs of (a) a banded snake (Bothryum lentiginosum), a lizard eater, and (b) a mangrove snake (Boiga dendrophila), a generalist feeding on both birds and lizards. The Boiga specimen was prepared with
the fang embedded in prey tissue, so only the base of the fang is visible; the prey tissue has separated slightly from the fang forming a clear venom tube (vertical arrow). (COURTESY: J. Leo van Hemmen)