The findings are published in the Journal of Experimental Biology.
This "circulatory arrest", the scientists say, is a much more efficient, rapid and definite way of finishing off prey than expected.
As the lead researcher, Prof Scott Boback, from Dickinson College in Pennsylvania, explained, restricting blood flow to the brain would also make a rodent "pass out within seconds".
The researchers believe that recording during a constriction could reveal useful details about how crush injuries cause complex tissue damage in humans.
But Prof Boback and his team are interested primarily in the fundamental question of how and why these snakes evolved their unique killing method.