Myth Debunked: Boa Constrictors Don't Suffocate Prey to Death

by Laura Geggel, Staff Writer | July 22, 2015 06:16pm ET

Boa constrictors are notorious for their deadly grip, squeezing their next meal until it expires. But scientists have long wondered whether this fatal hug kills prey by suffocation or by obstructing blood flow in the snake's victims.

Now, a new study finds that rats attacked by boas don't die from a lack of air. Instead, the boa's tight coils block the rat's blood flow, leading to circulatory arrest. That deadly grip helps to more quickly subdue rats and other prey that might be clawing back, allowing the snake to quickly end the struggle and preserve its energy, the researchers said.

"This is such an efficient behavior, and it allows us to realize that this behavior was really important in snake evolution," said lead researcher Scott Boback, an associate professor of biology at Dickinson College in Pennsylvania. "[Constriction] is extremely efficient at killing their prey and allowing them to be successful." 

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Snakes control blood flow in their 'spectacles'

Snakes can control blood flow in their "spectacles", scientists have found.

The animals are known for their lack of eyelids, and instead have a transparent scale covering their eyes for protection.

These "spectacles" contain blood vessels, and researchers investigated how this arrangement does not obscure vision.

They found blood flow changed when the snakes perceived a threat, allowing for optimal vision.

The study, by scientists from the University of Waterloo School of Optometry in Canada was published in the Journal of Experimental Biology.

"Reptilian spectacles are essentially the result of eyelids that fused and became transparent during embryonic development," said lead researcher Dr Kevin van Doorn.

"And because these are scaly animals we're talking about, a large scale covers its surface and is referred to simply as the 'spectacle scale'."

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