Croc Jaws More Sensitive Than Human Fingertips
Unlike crocodiles, alligators, such as this Texas specimen, have supersensitive dots only on their snouts.
They may be lethal, leathery, and literally armored to the teeth, but crocodiles and alligators, it turns out, are sensitive types. Their snouts, in fact, are even more touch-sensitive than human fingertips, a new study says.
Part of the crocodilian reptile order, alligators have some 4,000 of tiny, raised black spots, or domes, on their heads, particularly along their jaws, inside their mouths, and between their teeth. Crocodiles have a similar setup, plus a liberal sprinkling over the rest of their bodies, bringing their total to about 9,000.
Scientists have known about these bumps—called integumentary sensory organs, or ISOs—for more than a century. But for a long time their purpose was a mystery.
Perhaps, some biologists suggested, the domes have a waterproofing purpose. Or maybe they detect faint electrical fields given off by prey—or salt, to alert crocs to unsafe drinking water.
In 2002 an alligator study seemed to crack the mystery. Croc dots, it revealed, could detect ripples from even a single drop of water-and therefore even very weak prey movements.
Until now, though, a couple of big questions continued to intrigue scientists: How did the domes work—and just how sensitive are they?
Feeling the Unfeelable
Vanderbilt University student Duncan Leitch took it upon himself to solve the mysteries. The results of his croc research appear today in a Journal of Experimental Biology report coauthored with his advisor, biologist Ken Catania.
After taking a croc-handling course (pro tip: poke an unruly croc on the nose—especially sensitive due to those dots), Leitch ordered relatively small alligators from refuges and crocodiles from commercial breeders.
Shannon Fischer
for National Geographic News
Published November 8, 2012
