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And, now: A heart-stopping update on boa constrictors.

This is Sandra Tsing Loh with the Loh Down on Science.

In 2003, scientists found that constricting prey takes seven times more energy for the snakes than just resting.

You'd think boas wouldn't want to squeeze longer than they have to. Dickinson College biologist Scott Boback and colleagues thought so too--and wondered: How do boas know when to stop?

To find out, they implanted rat cadavers with two types of water-filled balloons: one connected to a pump to simulate a heartbeat, the other to a sensor to measure constriction.

Some rats' "hearts" were programmed to beat continuously, some for ten minutes, and others, not at all.

The researchers then dangled the reanimated rodents in front of 15 captive constrictors.

Results? Boas squoze rats with pulses twice as long and twice as hard as rats without pulses. They also adjusted their coils more often the longer the pulse persisted.

Which means boas use heartbeat as a cue to decide how hard to squeeze, and for how long.

Yikes. I'll never look at a blood pressure cuff the same way again. Just sayin'.



The Loh Down on Science, online, at lohdown.org. Produced by 89.3 KPCC and the California Institute of Technology, and made possible by TIAA-CREF.

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