"It was not something that we took lightly and we wanted to make sure that the animals did not experience pain or suffer," he said, explaining that the victims during the experiments were anesthetized.
The sedated rats were then lowered over hungry boa constrictors. Each snake strategically aimed its bite at the rat's head and then rapidly coiled its body around the rodent and began to squeeze.
Video: How Snakes Got Their Venom
ECG electrodes and blood pressure catheters applied to the rats revealed that their blood circulation shut down in a matter of seconds.
"I remember being in the room and the students were looking at the data in disbelief that it happened that fast," Boback said. "We could see the arterial pressure go down, the venous pressure go up and we could see this right when the snake was doing it ."
The researchers suspect that, without blood flow to the brain, any victim attacked in such a manner would pass out in a matter of seconds, helping to eliminate suffering on the part of the victim and, of course, making the process easier for the predator. After the victim passes out, other critical organs begin to fail, eventually killing the prey.
Boa Constrictor Mom Gives Virgin Birth
The research believe that early snakes didn't always have such abilities, and were limited to catching smaller animals. As the bite and squeeze technique evolved, it allowed the snakes to scale up the size of their meals, such that they can now sometimes kill prey that is larger than themselves.
Boback said, "By understanding the mechanisms of how constriction kills, we gain a greater appreciation for the efficiency of this behavior and the benefit it provided early snakes."