Boa Contrictors Kill Their Prey by Stopping Their Blood, Not by Suffocation

First Posted: Jul 23, 2015 09:37 AM EDT

It turns out that boa constrictors don't kill their prey by suffocation. Scientists have found that, in fact, these snakes kill their prey through another method: cardiac arrest.

"We have been studying constriction for a number of years," said Scott Boback, one of the researchers, in a news release. In fact, the researchers have been measuring the pressure exerted by snakes crushing dead rats in earlier experiments.

In this latest study, the researchers wanted to see what was going on inside the rat's victims. They first anesthetized the rats and then inserted ECG electrodes and blood pressure catheters into the rodent's body before offering the rat to a hungry boa constrictor.

In the experiment, the snake struck at the rat, aiming a bite at its head before coiling its body around the rodent. As the team watched, the blood pressure and heart rate data streamed onto the computer. The fat's blood circulation simply shut down in a matter of seconds. This shutdown causes no blood to flow to the brain, which causes the animal to pass out in a matter of seconds before other organs begin to fail. In other words, the prey doesn't die by suffocation.

Boas provide a glimpse into the evolution of crushing behavior in snakes. Ancient species that had not evolved constriction were probably restricted to capturing small meals they could subdue easily. Once the earliest boas had developed their quicker constriction technique, though, they were able to scale up the size of their meals and tackle animals that are larger than themselves.

The findings reveal a bit more about how these snakes kill their prey, and show how they're able to accomplish the feat so quickly.

The findings are published in The Journal of Experimental Biology.