Maureen Giesing, age 11, of San Diego, Calif., for her question:

HOW FAR CAN A MOLE BURROW UNDERGROUND?

This sort of nature work obviously calls for lots of patience. And even if we watch a busy mole all day and all night we cannot be certain that he is doing his best. However, the mole's remarkable digging activities have been clocked by several qualified observers. We know more or less how far and how fast he can tunnel below.

Some animals are busy during the daytime and sleep through the night. Some doze through the day and work at night. The busy little mole does neither. He lives in a world of total darkness where it is possible to ignore the natural divisions of night and day. As a rule, his calendar day is divided into work periods that last about four and a half hours, followed by three and a half hour rest periods. With this system he can do more digging and consume more food than one would believe possible.

For example, his elaborate system of tunnels may range through one tenth of an acre, often at three different levels. During his work shifts, he digs for grubs and worms at an inch or so below the surface. In a couple of hours he can tunnel six or eight feet  and maybe use the loose dirt to build a mole hill one foot wide and six inches high.

Below this foraging level he maintains a system of permanent horizontal tunnels at three to six inches below the surface. Here and there he has sloping paths that lead down to a second network of horizontal tunnels, perhaps a foot or more below the surface. And this is not all. Below the second level there are zigzagging shafts that dip down to three or four feet.

All this spade work is downright remarkable, especially for a small animal about five inches long. However, it is necessary because the little digger has such an enormous appetite. In order to supply his energy needs, every day he must consume enough food to equal the weight of his entire body. He does not hibernate, though in cooler climates he may tunnel deeper during the winter.  During a year, a mole    may devour more than 50 pounds of food.This includes a lot of destructive grubs and bugs, though, sad to say, most of his menu is earthworms, which are so good for our vegetable gardens. Sometimes he ties knots in earthworms and stores them in an underground pantry. And very often, his headless and half worms manage to escape and regrow their lost parts.