Alyson Watcher, age 10, of High Point, No. Carolina, for her question:

Why are there no snakes in New Zealand?

Not so long ago, scientists proved that the global map is on the move. Slowly, very slowly the continents have drifted apart. Islands appear and disappear. Strange as it may seem, this can explain why there are no native snakes in New Zealand. Drifting continents take their plant and animal populations on global tours. But their wild¬life fails to reach isolated ocean islands.

Out in the blue Pacific, some 1200 miles southeast of Australia, the New Zealand islands lie like neat tiles, garnished with bright greens, soft browns and sparkling white. The land area is about that of Colorado and, like Colorado, it has lush forested slopes, tall peaks and glistening snowcaps. These ocean islands have been isolated from the teeming continents, while life progressed through countless ages.

This may explain why New Zealand's wild=life is .very special. Many plants and animals developed there and nowhere else. New Zealand has sweet singing bellbirds and tui birds, non flying kiwis, kahes and kakapos. It has more than 1,200 assorted moths and butterflies, plus a poisonous spider and a couple of native bats. It has the one and only tuatara, a four footed reptile whose ancestors predated the dinosaurs. But New Zealand has no native snake to call its own.

This unusual wild life story goes hand in hand with the age old story of wandering geography. As scientists assemble the details, the history of New Zealand seems to fit into the moving global map. Some 200 million years ago, all the earth's land was a single continent in a single ocean. The earliest animals left fossil remains almost everywhere and ancestors of the dinosaurs wandered where they choose.

Gradually, the great land mass cracked and the pieces drifted apart to become separate continents. Chains of ocean islands rose and sank. Far south of Australia there was, and still is, a restless ridge in the deep ocean floor. Its fiery volcanoes erupted lavas to build up New Zealand above the water. It was populated with old style plants and animals, including the lizard like tuataras. But no snakes have been found among these ancient fossils.

Much later, during the northern ice ages, New Zealand sank down again below the waves. Most of its wild life was wiped out. But those old volcanoes never quit and in time they raised up the land again. And nature soon repopulated the new islands with a wondrous assortment of plants and animals. Most of the new tenants came from the faraway continents. But no snakes arrived, most likely because they could not crawl across the wide expanse of ocean water.

Four footed land mammals could not walk across to the new islands either. This may explain why New Zealand's only native mammals are a couple of flying bat species. Obviously, the squat, two foot long tuatara could not cross the water either. It would be nice to think that somehow he managed to cling onto a small speck of land when the rest of New Zealand sank beneath the sea    and waited there until the islands emerged again.