Boa constrictors are some big scary snakes. They can grow to as long as 10 feet or more and they are heavy. They are the largest species of the boa genus which includes pythons and anacondas. Their bodies are pretty much a long continuous coil of muscle and they aren't afraid to use it against their prey. Despite their deadly strength, they are non-venomous and often kept as exotic pets Many circus acts as well as daredevil performances have featured a snake handler wrapping a boa around his neck and shoulders while the audience watched in suspense to see if the snake would suffocate the handler. As it turns out, that isn't what constrictor snakes do at all.
A new study conducted by Associate Professor of Biology Scott Boback and a team of student researchers at Dickinson College in Carlisle, Pennsylvania has taken on the myth, which was accepted as fact almost everywhere, that the snakes kill their prey by suffocating them. What actually happens is that the snakes squeeze their prey and within a very short time the circulation of the unlucky captive is shut down. When the blood flow to major organs like the brain and heart is compromised, the animals pass out and die very quickly. The team found that death by this process, which is called "ischemia" is much faster than if the animal had been suffocated.
How did the team discover this? In order to get an accurate picture of what was happening to the vital signs of a prey animal as the snake was squeezing it, they had to use live animals, sedated of course, and these animals had to undergo complex surgery beforehand so devices measuring heart rate and blood pressure could be inserted and hooked up to collect the data.
In a statement from Dickinson College, Professor Boback said, "It was not something that we took lightly, and we wanted to make sure that the animals [rats] did not experience pain or suffer." He was quick to note in the press release about the study that the project proposal underwent a full review by the Institutional Animal Care and Use Committee (IACUC).
Boback's colleague Associate Professor Charles Zwemer and Emmet Blankenship, an Atlanta-based veterinarian, were part of the team as well as three undergraduate students who performed much of the surgery. Once the rats were anesthetized they were placed in a cage with a boa constrictor who had been waiting on a meal. The students observing the data being collected in real-time on the computers were astounded at how quickly the rats' circulation was cut off, sometimes in just a matter of seconds. This constriction caused the animal's heart rate to become irregular. Once the flow of blood to the brain was stopped, the rats passed out.
Boback has done earlier research on constrictors which showed that the snakes can actually sense the heart beat of their prey and adjust the force of their squeezing in response.
Check out the video below to see Professor Boback explain more about the study.
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