Why do some dogs walk by moving both legs on one side of the body at the same time, while others use diagonal pairs?

Dear Cecil: Why is it that some dogs walk by moving both legs on one side of the body at the same time, while others (most?) walk by moving the front leg on one side at the same time as the rear leg on the other side? Tim Silva, Washington, D.C.

Cecil replies:

You won’t believe this — I didn’t believe it, until I checked the files — but there is actually an answer to this question. Moving both legs on one side of the body forward at the same time is called “pacing.” It’s generally considered an easier, slower method of locomotion. Moving diagonal pairs of legs forward at the same time is called “trotting.” It’s more efficient since the body doesn’t roll as much and is usually regarded as a step up from pacing speed- and coordination-wise. There are many exceptions to the foregoing; some dogs can move pretty fast while pacing. Personally I’m content to locomote on two legs rather than four, except when I’ve had a very, very bad night.

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.