Can lizards breathe while running? April, Albuquerque, New Mexico

One cool spring day I hiked up the high mesa west of Albuquerque. A light, gray lizard with a squat toad-like body darted across the path. But then stopped. Was he catching his breath?

Probably yes. In 1987, biologist David R. Carrier of the University of Utah attached recorders to lizard bodies, and demonstrated lizards stop frequently to breathe. Furthermore, they do not breathe as they run. Later, he discovered lizards could breathe without braking to a complete stop, but only by pausing running motions.

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Since lizards cannot run and breathe, they, like sprinters, cannot sustain vigorous activity, says physiologist Gregory K. Snyder of the University of Colorado at Boulder. Most lizards exhaust muscle power after a couple of minutes, and take hours to recover the energy debt.

Lizards, like all reptiles and amphibians, evolved from fish. That's part of the problem. Fins became legs and feet, set far away from the body. Consequently, they walk and run in a "sprawling" way, says geologist Richard Cowen of the University of California, Davis. As a lizard steps on his right front foot for example, he flexes his trunk to the left and squeezes air out of his left lung and, therefore, cannot breathe using both lungs. So he breathes using both lungs only when his body is straight - between steps. At a walking pace, this works fine. But running steps twist the body so quickly there isn't time to breathe between them.

Breathing and running requires that the muscles in the body wall do two entirely different things: move the trunk laterally to run and move the ribs to breathe. They can do either one but "they can't do both simultaneously," says Carrier.

How fast do lizards breathe? Chris, Canaan, Connecticut

We have measured the rest breathing rate of the common dwarf gecko lizard ( Sphaerodactylus macrolepis). In 1975, physiologist Gregory K. Snyder (presently at the University of Colorado, Boulder) found that the lizards breathe about 39 breaths per minute, but the rate varies with temperature. As the outside temperature increases from 70 F to 81 F (21C to 27 C), the lizards breathing rate increased from 24 to 39 breaths per minute, and remained steady at 39 breaths per minute for temperatures from 81F to 91F (27C to 33C). For comparison, the average breathing rate in a healthy adult human is about 12 breaths per minute.

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