Python with an impala.

Constriction is a method used by some snakes to kill prey. While a few venomous snakes employ constriction, most constrictors lack venom. The method involves the snake grabbing its prey with its jaws and wrapping a number of coils around it. With each breath, the snake tightens its grip further, until death from axphyxiation, though it has been suggested that cardiac arrest is a possibility: this would almost certainly kill prey faster than the former. The snake's belly scales are sensitive to the prey's heartbeat, which allow the snake to ascertain the prey's death. Constriction allows for quicker capture, and due to the high requirements for a constrictor's size and muscle mass, allows prey as large as antelope to be consumed by those among the largest species.