January 19, 2012

Eva Gusnowski

As a first year medical student, I can tell you very little about actual medicine, aside from all of the problems that I am currently convinced that I have. What I can tell you is that a pulse is pretty important. But you didn’t even need me to be the one to tell you that…you could have just looked to the boa constrictor.

In order to kill their prey, boas tightly coil and squeeze around their victim. Each inspiration results in more constriction, eventually preventing any breathing at all. But in and of itself, constriction is an energetically costly process, demanding almost seven times as much energy generation compared to just hanging out, and can last for upwards of 15 minutes. This also places the boa constrictor at risk for harm from its victim, or from other predators. It would make sense then for the snake to monitor whether they should squeeze harder, or if they need to continue constricting at all.


science in seconds, snake-ometer, boa constrictor

Bring in the snake-ometer: not recommended for home pulse analysis, but it works pretty well in the wild.

Scott Boback and colleagues looked at whether a boa constrictor monitors the pulse of a victim and modulates its constricting pressure accordingly. To perform this analysis, they took dead rats and inserted an artificial heart and pressure monitors. The snakes were provided with three scenarios: 1) an artificial heartbeat throughout the constriction; 2) an artificial heartbeat which was turned off after a specified amount of time (10 minutes) or; 3) no heartbeat.


snake-ometer, boa constrictor

It was found that the snakes adjusted their coils frequently while there was still a heartbeat in the cadaver-rat. However, coil adjustments were essentially absent when there was no heartbeat at all. Additionally, the researchers noted that the boas constricted rats with a heartbeat for twice as long as those without a heartbeat, and had a tighter constriction pressure when a heartbeat was present as well. If the heartbeat was discontinued after 10 minutes, snakes constricted with a pressure and a time length approximately midway between the other two values.


These same differences were noted in both wild boa constrictors and captive-bred constrictors that had never been exposed to live prey before, implying that this ability is innate within the species…much like being a scientist and loving nerdy jokes. It just happens.

So if all else fails, you can always ask the boa constrictor to take your pulse…just don’t expect to be getting that arm back any time soon.  Maybe ever.  (More likely never.)



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