Mike Justis, age 12, of Eugene, Ore., for hIS question:

What is estivation?

When a frog sinks into a deep coma, he may be estivating. His froggy mouth is shut and the lower eyelids are closed over his bulging eyes. His breathing and his heart beat are so slow that you might mistake him for dead. You might also mistake him for a hibernating frog.

In Oregon and other temperate regions, we are 1lsed to the idea that many animals hibernate through the winter season. These fellows are, we might say, winter sleepers. But the animals of the deserts and the tropics must cope with different weather problems. Some of them cannot abide the long droughts or the scorching mid summer heat.

Many of the hot climate animals go into estivation to escape the hardships of summer. The estivator, we might say, are the summer sleepers. An expert would find it hard to tell whether an animal were hibernating or estivating  unless he knew where it was found.

Actually, these animals sink into a coma which is deeper than the deepest sleep. The frog can hibernate or estivate, depending upon where he lives. In the desert, he may hide among the rocks and. Estivate through the mid summer heat. In the mud flats of Australia, he may have to cope with a drought lasting a year or more. Here he burrows himself into the mud, which may turn into a wad of sun baked clay, no matter. When the rains finally come, the estivating frog will come back to life. The tropical swamplands of the crocodiles and alligators often suffer droughts lasting for months. These water dwelling reptiles so1ve the problem by burying themselves in the mud and estivating until conditions improve. The mud nary seal them in solid clay, but the rainy season will set them free and awaken the hungry fellows.

Many snails of the tropics also estivate when the climate becomes too hot or too dry for comfort. Some of them use a wad of mud, to plug up doorways to their shells. This seals in the moisture, and the estivating snails spend the waiting period in air conditioned chambers. At least one snail has been known to estivate for years. But many animals go into estivation only at certain seasons of the year, and they sleep only for a certain length of time.

The lung fish of Africa is one of the most gifted of the estivating animals. This amazing fellow has lungs which he uses to gulp air from above the water. He prepares for estivation by eating extra food and adding a layer of fat to last him through the waiting period. Then he burrows down deep and curls his tail around to his head. He rests in a flask shaped roll with a tunnel from his mouth up to the air above. The room and tunnel are lined with mucus to seal. In the moisture.