Snakes such as pythons and boas “feel” the heartbeat of their victims as they are slowly asphyxiated to decide when it is safe to loosen their grip.
New research led by Dr Scott Boback, a herpetologist and professor of biology at Dickinson College, Pennsylvania, has revealed this unnerving serpent trait.
“We looked at what might be the cue that allows snakes to determine when it might be safe to release their prey during a constriction event,” explained Dr Boback.
Dr Boback’s team used a dead rat fitted with an artificial heart to simulate the prey of constricting snakes. The rat’s body was also warmed to mimic a live rat. This allowed them to isolate the heartbeat from other vital signs, which the snakes use to decide when it is safe to release their victims. The research showed that, once the heart had stopped beating, the constrictors relinquished their victims and began to feed.
Dr Scott Boback talks constrictors (mp3)
Constrictors will typically hunt animals that are between 15-20 per cent of their body mass, such as small birds or rodents, although they have been known to kill much larger prey. The snake family has evolved an expansive armoury and employs a wide range of methods to successfully detect, identify and ultimately dispatch their prey.
Constrictors, as ambush predators, surprise their prey and wrap tightly around it, using their muscular bodies to prevent the animal from inhaling. The snake can feel each time the animal exhales and tightens its grip to slowly suffocate the animal.
This process has been understood for some time but, until now, scientists had no idea that snakes were also monitoring the heartbeat of their quarry. The constrictors apparently use the cue to determine when to release their hold, as an animal that is still alive might escape or attack the snake.
Many people view snakes as audacious killers, incapable of the complex functions we typically reserve for “higher” vertebrates. This research wonderfully illustrates that misconception and highlights one of the key advancements that forged the success of the entire snake group.
Image courtesy of Eisen Jiao