Boas take pulse as they snuff it out

Snakes use waning throb as signal to stop squeezing

A boa constrictor knows to stop squeezing a juicy rat by sensing the heartbeat of its prey, easing up only when the pulse stops, a new study finds.

TIME OF DEATH A boa constrictor takes the pulse of a dead rat implanted with an artificial heart, letting go only when the faux vital sign disappears.