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Inventors put big squeeze on snakes

Animal Planet show to feature CMU's reptile meter

Sunday, March 03, 2002

By Bill Schackner, Post-Gazette Staff Writer

When an 18-foot-long predator snake gets hungry, how hard will it squeeze its prey?

Believe it or not, there is a scientific answer, thanks to a contraption some are calling the "Constrict-o-meter."

British Broadcasting Corp. director and producer Yvonne Ellis and Pittsburgh Zoo and Aquarium reptile keeper Herb Ellerbrock talk during the taping of a documentary about snakes yesterday at the zoo. (Gabor Degre, Post-Gazette)

It probably won't win a Nobel Prize for them, but Carnegie Mellon University professor Adnan Akay and his colleagues have nevertheless developed what they believe is the only device of its kind.

Yesterday, as a British television crew hovered nearby at the Pittsburgh Zoo and Aquarium, three Burmese pythons provided Akay with an opportunity to test the device as the snakes noshed on frozen, 10-pound rabbits.

It all began when creators of a show due to air this fall on the Animal Planet cable television network set out to learn the constriction pressure exerted by a snake while killing its prey. They approached zoo reptile keeper Herb Ellerbrock, who in turn contacted Akay, head of the mechanical engineering department at Carnegie Mellon.

Workers from both organizations spent two months on the project that culminated with yesterday's demonstration. It will be part of "The Big Squeeze," an hour-long show.

"Personally, what I learned was a lot more about snakes than I ever wanted to know," said Akay after one of the creatures, weighing 160 pounds, finished its meal and was hauled away.

"One is that, as opposed to the common belief that a boa constrictor squeezes its prey and crushes it, it doesn't. It really suffocates it."

The device Akay used is a load sensor attached to a foot-long aluminum probe that is placed between the snake and whatever it is squeezing. The device, linked to a laptop computer, generates electrical signals as the snake constricts.

"A signal proportional to the pressure that the snake applies is sent to a data acquisition system, and then we store that information and analyze it," Akay said. "While we are making a measurement, we can monitor the change in pressure and the amount of pressure on the computer screen."

Readings from the snakes tested yesterday suggested that an 18-foot-long snake applies pressure equal to about 12 pounds per square inch. A smaller snake, say 5 feet long, might exert the equivalent of 6 pounds per square inch as it wraps itself around its prey.

As is true of any research, the unexpected sometimes happens. While British Broadcasting Corp. crew stood just a few feet away, one of the 18-foot-long snakes slipped below a table and took hold of the reptile keeper.

"It's got Herb's leg," said a woman.

Not to worry. The keeper, who had volunteered the use of his arm for a couple of the tests, hardly seemed fazed. The creature let go in moments, and the crew was back filming the snakes at work.

Yvonne Ellis, a BBC director and producer, looked pleased by what she saw.

"This is very good television," she said.
