We initially thought that boa constrictors like pythons and anacondas killed their prey by asphyxiation, or cutting the animal's airflow and depriving it from oxygen. However, research has suggested that boa constrictors stop the blood flow of their prey, causing immediate death from cardiac arrest.
The difference between asphyxiation and sudden cardiac arrest is that in the first situation, only the airways are constricted, but the heart continues pumping blood throughout the body. In this scenario, one would assume that the prey caught in the stranglehold would try to free itself and show signs of a struggle.
But this anecdote by a doctor who had witnessed the killing of a goat by a python indicated that there had been no signs of a struggle, but he observed depressions on the goat's chest. Granted, this is just one anecdote and the doctor did not investigate further.
Scientists who conducted experiments, however, have been able to figure out exactly how boa constrictors killed their prey. They attached sensors into anesthetized rats and a python in order to measure the rats' blood pressure, blood gases, blood ion balance, and heart function, as well as the amount of pressure that the python was exerting on the rat.
From the experiments, they found that the pythons had been exerting immense pressure on the rats' blood flow at a rapid pace. It caused instantaneous cardiac arrest. Again, a few caveats: rats are mammals, and quite small. So, attacking its circulatory system would entail instantaneous death.
On the other hand, if boas will try and constrict lizards or frogs, for example, will the manner of death be the same, considering cold-blooded animals don't have the same circulatory systems as mammals? This is a question for a future study.
But it makes sense why sudden cardiac arrest is more advantageous for boa constrictors.
First, it eliminates the possibility of harm when the prey struggles. In the example of the rat, it may use its claws or teeth to gnaw away at the python. Or, in the case of the goat, it may use its horns to stab the python or its hooves to trample on it.
Second, it saves the snake time and energy in hunting and eating its prey.
At the end of the day, I think the lesson is the same. Stay away from boa constrictors.
(Image credit: Jan Kopřiva/Unsplash)