News Life Boas take pulse as they snuff it out Snakes use waning throb as signal to stop squeezing By Devin Powell January 18, 2012 at 11:59 am - More than 2 years ago Share this:Share Share via email (Opens in new window) Email Click to share on Facebook (Opens in new window) Facebook Click to share on Reddit (Opens in new window) Reddit Click to share on X (Opens in new window) X Click to print (Opens in new window) Print 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.