It's harder work being a snake than scientists once believed.
Three University of California at Irvine scientists studying the energy cost of locomotion say that it takes as much energy for a snake to undulate along the ground as it does for an animal with legs to walk.This, says Bruce Jayne, a co-author of a study published Friday in Science, is contrary to what scientists have long believed.
"Our findings do not support the widely held notion that the energetic cost of terrestrial locomotion by limbless animals is less than that of limbed animals," he said.
In plain language, it is as hard to wiggle along as it is to walk along. Or it takes as much energy to slither as it does to stroll.
To find out how hard a snake has to work to get from one place to another, Jayne and his colleagues got a group of black racer snakes and figured out a way to put them through an aerobic workout.
First, the 3-foot-long snakes were fitted with little clear-plastic masks. Leading from each mask was a hose to collect the exhaled reptilian breath.
Then the snakes, one by one, were put on a treadmill - or, perhaps, a slithermill.
Anyway, once placed on the device, a snake crawled like crazy to keep up with the surface moving under it. As it worked, the snake's exhaled breath was drawn through the hose and into a machine that measured the oxygen content.
How much oxygen was depleted from the breath, said Jayne, was a measure of the amount of energy the snake needed to slither along.
The scientists then compared the results with similar studies of limbed animals, such as lizards, of the same mass or weight. The energy used by both the footed and the fanged was about the same, they discovered.
Jayne said the study casts doubt on a long-held notion about the evolution of limbless land animals, such as snakes and some legless lizards.
"One explanation for the evolutionary loss of limbs has been that it was energetically less expensive," he said. Jayne said scientists have suggested that being legless gave some animals an advantage because it was thought to require less energy to move like a snake than to walk on legs.
Now, he said, that theory no longer seems valid.
Jayne said the undulating motion of a snake on a flat surface is only one of several ways the reptile can move.