The idea of suffocating in the grip of a boa constrictor's coils is enough to make anyone gasp for breath with worry. However, some keen-eyed researchers thought that suffocation might not be the true cause of death from a boa constrictor. Instead, it was found that boa constrictors do just that: constrict their prey to death.
Death by suffocation seems logical. The constrictor wraps around the chest and neck of prey, restricting their breathing apparatus. However, Dr Scott Boback, a researcher from Dickinson College, noticed that the animals were killed too quickly for their cause of death to be suffocation, so he decided to do some detective work.
The team decided to set up an experiment to find out exactly what was going on inside an anesthetized rat that was caught in the clutches of a boa constrictor. As described in the Journal of Experimental Biology, the rodent was fitted with blood pressure catheters and ECG electrodes so that the research team could monitor its vitals.
The team may have already predicted the true cause of death, but they could never have predicted how efficient it was.
Boback summarized to IFLScience that there were two main surprises in their results, "One was the speed at which these things occurred." The boa constrictor was shown to constrict its prey to death before suffocation took place.
"Within 30 seconds of the snake starting to constrict, the rat's arterial pressure was plummeting," Boback commented. Interestingly, as soon as the constriction pressure from the snake increased, the pressure in the rat's arteries decreased with respect to one another.
"The other thing that we were really surprised with: there's multiple bad events that are occurring for the rat; it's not just the arterial pressure that goes down, we also measure other things like potassium."
Everyone needs potassium in their bodies to regulate how fluids and minerals flow in and out of cells. It's normally regulated in a tight window. However, Boback and his team were startled to see that the rat's potassium levels increased dramatically as it was constricted.
Boa constrictor coiled around anesthetized prey. Scott Boback.
Boback mused that this strategy made sense when you see how fast the prey's vitals drop. As soon as blood flow stops, the brain fails very shortly after and the animal passes out. "Actually the very very first thing that probably happens is that the rat passes out, and this makes strong evolutionary sense. If the snake causes the rat to pass out really quickly, then there's no danger from that animal retaliating against you," Boback explained. An animal that has passed out is much easier to subdue and eat than one that is struggling.
In the future, Boback and his team are interested in studying the effects in other sorts of prey. Rats and mammals are known as endotherms or "warm-blooded" animals. Boback wonders if the effects of constriction and blood flow are different for ectotherms or "cold-blooded" animals such as lizards. "It would be really interesting to study the results of constriction on ectothermic prey."