We Finally Know Why Boa Constrictors Don't Choke While Crushing Their Prey to Death

Powerful ambush hunters like the boa constrictor snakes are notorious for incapacitating their prey by squeezing them to death before swallowing them whole. Researchers have found a way for the snakes to achieve this.

Contrary to popular belief, these nonvenomous reptiles kill their victims by suffocating them, rather than by cutting off their blood flow. This technique allows them to take down large prey, including wild pigs, monkeys, and ocelots from their forested homes in Central and South America.

The thin layer of muscle mammals like us contract to move air in and out of lungs so they rely entirely on their rib muscles to breathe. When the muscles are busy squashing something or squeezing food through their bodies, snakes cannot move air around.

The nocturnal nope ropes increase oxygen consumption by almost 7 times while subduing their victims compared to resting rates, and up to 17 times to digest prey a quarter of their own body weight. How boa constrictors can squeeze the life out of another animal for up to 45 minutes has been a long-standing mystery.

It sounds like a risky task, but researchers from Brown University used blood pressure cuffs to figure out what happens when different parts of a danger noodle are mangled.

The team was able to measure some big breaths because the reptiles filled their lungs to hiss, and either the animals did not mind the cuff or became defensive and hissed to try to get the researcher to leave.

The team could assess and reconstruct how the boa's ribs moved by compressing the cuff along different points. When the ribs closest to the snake's head were stifled by the gripping cuff, ribs further towards its tail started to heave in and out.

The front part of the snake would move if the cuff gripped the back ribs.

boa constrictors can change which part of their rib cage they use for breathing to save themselves from suffocating.

Capano and colleagues believe that this newfound ability evolved before snakes began to constrict their prey.

While long, noodle-shaped bodies have evolved at least 65 times amongst animals with backbones, snakes have the most stunning array of diversity out of all these groups. The ability to take down a large victim and swallow it whole may have been what gave these animals their edge, according to some researchers.

The ability to subdue and consume such massive prey may have been a key feature in snake evolution.

The Journal of Experimental Biology published this research.