Deborah Snider, age 10, of Winston Salem, North Carolina, for her question:
Why are there no snakes in Hawaii?
A century or so ago, there were no snakes in Hawaii. Then at least one snaky character arrived and made himself at home there. Of course, this immigrant is not a native of long standing and we can say that he does not rightfully belong in the natural ecology of the islands. There are no native snakes in Ireland either. New Zealand is snakeless, so is Alaska and several other parts of the world.
Snakes are fond of mild climates where the softish ground remains unfrozen through a long season of spring and summer. You would think that the Hawaiian Islands would suit them just fine. So they would if the snakes could find a way to get there. But they are not global travelers by nature. True, they manage to slither short distances, traveling very gracefully, considering that they have no legs. But crossing continents is too much for them. And land snakes cannot cross oceans or even smallish stretches of water.
Scientists tell us that their ancestors were lizards that scuttled along on squat stubby legs. Perhaps 100 million years ago, these snaky ancestors changed their life style. They wiggled around and gradually gave up walking altogether. Mother Nature never lets her animals keep useless items. So gradually the lizards lost their unused legs and became snakes.
It seems that this patient remodeling job happened on the continents and large land masses. And this is where almost all of the non traveling snakes had to stay. None of them reached Hawaii until recent times. It seems that a certain immigrant called the Indian Blind Snake managed to get past the customs officials. Some suspect he was concealed in some cargo unloaded from a ship. Obviously his wife and perhaps other relatives came along too. Because this snake species multiplied and made himself at home in Hawaii.
During the past 100 million years, the earth has shifted the shape of the global map. The continents drifted farther apart. Seas and glaciers cut off sections from some of the land masses.. There are plenty of native snakes in Australia, but none managed to cross the sea to nearby New Zealand. Until recently, no snakes managed to cross the ocean to Hawaii and other Pacific islands.
One brave viper dares to live in northern Scandinavia, just inside the Arctic Circle. But the rest cannot abide these cold tundra regions, where the ground below the surface is always frozen. This may explain why there are no native snakes in Alaska and other far northern parts of Europe and Asia.
Perhaps there were once snakes in Ireland, but the ice age glaciers must have crushed and frozen them. About 32 species survived farther south in Europe. When the ice melted, the flood water cut off Ireland and then England from the mainland. Three of the southern snakes had time to crawl to England. But not one species managed to crawl back to Ireland.