There's an old song that you might remember: "Tiptoe Through the Tulips". As is obvious from the song and from everyday life, we tend to think walking on tiptoes is unusual—and so it is for us. Many mammals, though, would find it unthinkable to proceed in any other way. Animals we're all familiar with would find it as difficult to walk on the whole foot as we do on tiptoe.
Mammalogists have a word for it, of course: digitigrade. Digits are
fingers and toes, and "grade" refers to step: thus those who are digitigrade
are using the digits to step. Observe your cat or dog. That backwards-pointing joint
part way up the leg is the heel, for these animals do indeed go about on tippytoes. Of
course, there are other mammals that make these look like novices in the toe-walking
business. Horses not only go another step further by contacting the ground only on the
very end of a digit, but each foot ends on only a single toe. Let's see your
ballerina top that one!
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.