Super Snake

Brad Moon Snakes inspire both fear and fascination in us, and rightly so. Venomous snakes and even some non-venomous snakes—such as the giant constrictors—can be lethal to humans and animals much larger than the snakes themselves. How strong are giant constrictors and how do they take down such large animals? I joined a team from National Geographic Explorer to find out. It’s constriction, not suffocation… Constriction is a method snakes use to subdue their prey, by coiling their muscular bodies around their otherwise unwieldy victims and squeezing, the constriction prevents even their largest prey from biting or kicking their way free from the snake’s grasp. Constriction was a critical evolutionary innovation that enabled snakes to expand their diets, which now range from ants to antelopes. It also enabled snakes to diversify in body form—without constriction, snakes may not have evolved into the species we have today. Traditionally it was believed that constrictor snakes killed their prey by suffocation, by squeezing their victims so tightly they could no longer breathe. But suffocation can take up to several minutes, which can give a prey animal plenty of time to fight back, and we now know that prey animals are often killed much faster than that. A second explanation for how constriction kills so quickly is that it squeezes the blood vessels closed and causes the circulation to stop. If constriction is strong enough to squeeze the blood vessels closed in the body of a prey animal, then the animal’s circulation stops immediately, which causes the tissues to run out of oxygen and die in seconds rather than minutes. More recent observations on wild anacondas and their prey in the Venezuelan llanos, revealed that they can break the necks of prey animals as large as caimans, capybaras, and deer. These observations suggested that giant constrictors can be extremely strong, but their actual strengths had never been determined. How strong is strong? Before this project, only the strength of small constrictors had been studied. Several years ago, I measured the pressures exerted during constriction by snakes that were approximately 3 ft long and 1.5 inches thick. Constriction pressure is a good measure of a snake’s strength and it is one of the key components that restricts prey movement and kills it. To measure the pressures, I used small balloons attached to a prey animal and connected by tubing to a pressure transducer that gave a digital readout of the constriction pressure exerted by the snake’s coil. I discovered that even small constrictors can squeeze with pressures up to 4 PSI (pounds per square inch). This is strong enough to squeeze blood vessels closed in mice and kill them by circulatory arrest. This result was very important because it showed that the traditional explanation of constriction causing suffocation was probably wrong. The difference is crucial, because circulatory arrest kills prey animals much faster than suffocation, making it a safer and more surefire method for the snakes. But large prey animals such as capybaras and deer are much stronger than mice and rats, and so, much more dangerous to the constrictors. How do constrictors subdue such large prey animals? To find out, we traveled to the llanos region of Venezuela in search of a large anaconda (Eunectes murinus). At Rancho Doña Barbara , we measured constriction by an anaconda that was about 18 feet long and 6 inches thick. This star performer was an amazing animal that took four people to handle safely when we weighed and measured it. he snake constricted one of its favorite prey animals—a local kind of duck—with incredible strength and stamina. The strengths we measured indicated that anacondas can easily squeeze hard enough to take down much larger prey animals with little chance of their escape or retaliation. In fact, if a big anaconda managed to ambush a person, the results could quickly be lethal! It probably wouldn’t matter how big the person is or whether a partner was present to attempt a rescue, because a big constrictor becomes a ball of muscle that feels like solid rock and is just too strong to peel apart. And our anaconda wasn’t especially large—the largest individuals reach lengths of nearly 30 ft and diameters over 12 inches. These gigantic constrictors remain to be measured, but we now know that they must be incredibly strong!
Categories: Animals, Snakes, South America
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