When two snakes fight, it can be hard to work out who’s winning. “They’re both wound together, just two tubes wrestling,” says David Penning, from the University of Louisiana at Lafayette. But if one of the combatants is a kingsnake, then all you have to do is wait. The kingsnake will be the one left slithering.
These animals get their name because they specialize in killing other snakes. They’ll take rodents, lizards, and birds as well, but snakes account for a quarter of their diet. They do so by constriction—wrapping their coils around their opponent and squeezing so hard that they trigger cardiac arrest.1
The kingsnake will launch itself at, say, a ratsnake, bite it, and throw some coils around. Then it inches its way toward the victim’s head, alternating between shifting its bite and adding more coils. The ratsnake tries to escape, but almost never does. Penning has now watched hundreds of these bouts, and “it never ever seemed like the kingsnake is in trouble,” he says. Unless it’s a juvenile that has inadvisedly picked on a target several times its size, it always wins. And, to Penning, that made no sense.
Typically, when scientists study constrictors, they look at big ones like pythons or boa constrictors, as they attack mice or rats. “Big snakes are strong predators; small mammals don’t do well when squeezed,” says Penning. “Rarely is someone surprised when the snake wins that scenario.” But kingsnakes will successfully constrict victims that are the same size or bigger, and that are also constrictors. How do you kill something that’s larger than you, using the very same method that it uses to kill? Why don’t kingsnakes ever get counter-constricted?