Typically, the animals are about 12 feet (4 meters) long, a foot (30 centimeters) in diameter, and weigh several hundred pounds (75 to 150 kilograms). While other snakes can grow longer, they cannot match the anaconda's length and bulk.
Killing With Stealth and Strength
The massive snakes may eat only a few times a year, but when in the mood for a meal they are a formidable animal to be respected by anything or anyone in their area.
Constrictors hunt by ambush, as do many other snakes. It's their method of killing and consuming their prey that has made them the stuff of legend.
"What she does is try to squeeze the heart of the animal so tight that it can't fill up with blood," Rivas explained. "Then there's a total circulatory arrest in the animal." The snakes also twist while constricting, in order to break the backs of their unfortunate prey.
"Most snakes just eat their prey alive," Rivas continued. "But constrictors eat prey that is too big, animals that could do the snake harm. So they have to kill it first. These animals developed a way to kill without claws, or cutting teeth."
While the anaconda can deliver a painful bite, the animal's head is quite flexible and has mobile hinging jaws that are unable to deliver a really crushing bite. The adapted skull, however, serves another purpose: it gives the snake the ability to swallow prey wholeincluding animals of human size or even larger.
Anacondas have long been known as "man-eaters." Although such an event is a terrifying thought, few deaths have been recorded. "The reason that they don't eat people is that people don't come into contact with these snakes very much," said Rivas. "But even a medium-size snake could kill a full-size person."
Birds are much more common victims. Snakes smaller than 10 feet (3 meters) dine primarily on birds. Bigger anacondas tackle other prey like caiman, turtles, white-tailed deer, and the capybara, a pig-sized rodent that Rivas describes as "kind of a hybrid between a hippo and a chipmunk."
While a decade of wrestling snakes represents a lot of work, Rivas explained that his study is far from finished and that science still has much to learn about the constrictors.
"In general the biology, reproduction, diet, and lifecycle of these animals in the wild are very poorly understood," he said. "These animals live for probably 20 years or maybe even 40 yearsso studying them for 10 years is not going to get you the whole picture. The animals I caught in 1992, well, I caught them again this year, so they are still alive. They might outlive me for all I know. It's a challenge. Studying natural history in the wild takes time. When you are studying an animal that lives for 30 years you need to follow it for at least that long."
SOURCES AND RELATED WEB SITES