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Boa constrictors famously use their bodies to squeeze prey to death, and the snakes have to do this without suffocating themselves in the process. NPR's Nell Greenfieldboyce reports on how boas perform this trick.
NELL GREENFIELDBOYCE, BYLINE: A classic nature documentary scene is a boa constrictor taking on some big animal, like a wild pig. The snake has got to grab it in its mouth, coiled around it, and then later swallow it down whole.
JOHN CAPANO: Some species of snakes, like boas and pythons, will eat something about their own body size, sometimes about 100% of their own mass.
GREENFIELDBOYCE: John Capano studies snakes at Brown University. He says the trouble is all of that means the part of the snake's body near its head, where the ribs usually are drawing in air so it can breathe, are pretty preoccupied with either clamping down to crush the prey or opening wide to take it in.
CAPANO: Its rib cage is kind of spread out to accommodate that thing inside of it. So there's the chance that they can't move their ribs anymore, because they're already, like, at capacity.
GREENFIELDBOYCE: So the question is, how exactly do they breathe? A while back, Capano and a colleague were feeding snakes and noticed that ribs farther down towards the tail seemed to be doing the breathing work. They eventually did a bunch of studies to explore this. They'd immobilize part of a snake's length by inflating a blood pressure cuff around it, then use X-rays to monitor the movements of its ribs.
CAPANO: You can see that the ribs will stop moving when we put the cuff on the front, and they'll start moving in the back. And if you take the cuff off, they stop moving in the back, and they go back to the front.
GREENFIELDBOYCE: The results appear in the Journal of Experimental Biology. Having this control over breathing must have been super important as snakes first started making their living by constricting. Elizabeth Brainerd is one of the scientists at Brown who worked on this study.
ELIZABETH BRAINERD: As constriction was evolving, it was certainly impeding the ability of those animals to use the ribs in that area for breathing.
GREENFIELDBOYCE: She says there had to be this workaround. Jake Socha thinks this is a cool finding. He's a biomechanics researcher at Virginia Tech.
JAKE SOCHA: This is a really key, important study in helping to explain what might have made snakes so successful.
GREENFIELDBOYCE: Snakes have been very successful. Their long, limbless bodies have proven very adaptive to the point where they can squeeze a big animal to death without losing their breath. Nell Greenfieldboyce, NPR News.
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