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Leashing the rattlesnake: a behind-the-scenes look at experimental design

Science News, Sept 27, 2003 by Susan Milius

Depending on how you look at them, snakes have no neck or nothing but neck, and either way, Ron Swaisgood had a problem. To finish his Ph.D. at the University of California, Davis he had to figure out how to put a rattlesnake on a leash. Obviously, dropping a slipknot around the snake's neck wouldn't do. Swaisgood's research project required that the snake comfortably slither, coil, and strike but still be tethered tightly enough that there was no chance it could escape.

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Swaisgood eventually developed a great snake leash, finished his degree, and proceeded to his current job at the San Diego Zoo. The scientific paper based on the research just says he tethered the snake and then goes on to describe the ways that ground squirrels assess snakes as threats (SN: 10/9/99, p. 237). The leash joined thousands of other little unsung triumphs of creativity in experimental design that don't usually show up in scientific articles--or reports in Science News. Ask for the details, though, and another side of research appears. Here, many biologists say, is a lot of the fun.

Experimental science demands creativity in solving problems great and small, and the study of animal behavior makes a dramatic showcase for the process. Animals clearly have minds of their own, and to elucidate such foreign perspectives, researchers have to design cleverly, from the basic strategy of the experiment to dozens of lesser details. The traditions of animal behavior celebrate do-it-yourself flair, and experiments mix the sublimely high tech with the ridiculously simple. Consider the snake leash.

Swaisgood reminisces that the first Northern Pacific rattlesnake he'd caught for his experiment "was kind of a phlegmatic snake." The university veterinary surgeons who frequently prepare animals for experiments gave the rattler an implant of a little plastic loop. Swaisgood then just clipped a line to the loop and staked the snake in place.

The next snake, however, had a completely different personality and moved vigorously. A loop implant didn't look like a good idea. "We were concerned he might hurt himself, Swaisgood says. "We started going through our tackle box of research gear looking for something else." He finally leashed his rattlesnake by attaching fishing line to it with--bonus points to readers who saw this coming--that icon of invention: duct tape.

FOOLING MOTHER NATURE The core of an experiment in behavioral science depends on changing one thing about an animal's world but leaving everything else the same. This challenge sometimes demands a mix of scientific sophistication and parlor tricks.

Ken Kardong couldn't use a silk handkerchief as a blindfold since the eyes he needed to cover belonged to a rattlesnake. After Kardong's lab at Washington State University in Pullman had documented the biomechanical marvels of the snake's strike, he began thinking that the snake's sensory systems needed to be equally marvelous to take advantage of that natural engineering. He decided to study how the snake's senses contributed to strike targeting, so he wanted to block, and then restore, each of its senses.

Snakes' eyes carry a dear, protective layer that lacks the nerve endings that make human eyeballs so tender. "It's like they're wearing glasses," says Kardong. So, with a conventional snake-handling stick, he held a rattler down on a counter, got a firm grip at the back of its head, and placed a patch of black electrical tape over each eye.

Kardong next had to invent another kind of blindfold, this one for the infrared-sensing pits on the snake's face. Depending on the size of the snake, the pair of pockets varies from depressions the size of a pinhead to pits that could hold a BB.

Again, Kardong thought of electrical tape, but he wanted extra insulation to block heat. At first, he considered rolling up little balls of paper. Then, a brainstorm came from a Styrofoam coffee cup. He sliced it into strips and rolled bits between his thumb and forefinger until he had the right size for each snake.

Kardong says, "My definition of cleverness includes simple. Blindfolding either the eyes or the pits, by the way, made no difference in the accuracy of a rattlesnake's strike. Sight or heat sensing was sufficient on its own.

Other scientists have also needed to jam and unjam a sensory organ. For instance, Alejandro Purgue invented earmuffs for bullfrogs.

Now at Cornell University's Laboratory of Ornithology in Ithaca, Purgue had been studying the acoustics of North American bullfrogs. He began to suspect that the power of the male's commanding "ribit" came not from the throat but from vibrations in ear membranes. Purgne needed to damp and then release the membranes to document any differences in calls.

He tried smearing globs of standard laboratory silicon grease on the membranes to prevent them from vibrating. However, cleaning grease off the frogs' ears to reverse the effect turned out to be a nuisance. So, Purgue cut little ear pads out of the shock-absorbing foam used for inserts in running shoes. (He bought the foam at a supply company; no shoes were harmed in this experiment.) To link the pads, Purgue wound a tiny, tight coil of piano wire into a spring that would go over the frog's head.

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Leashing the rattlesnake: a behind-the-scenes look at experimental design

Science News, Sept 27, 2003 by Susan Milius

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