Jimmy Stewart,, age 10, of Waynesboro, Va., for his question:
Why did the kangaroos survive in Australia?
This is a story of competition. And competition is not an easy idea to grasp, for there are two kinds. One kind of competition is between human beings and it applies when you run a race, play a game or try for top grades, The other is the merciless competition which goes on in the world of nature.
When you run a race, you put your best foot forward and try to win. But whether you win or lose, you have a good feeling if you understand competition correctly. This feeling comes just from doing your best. When you play a good game, you share a feeling of pride with your team. But in the world of nature, competition is far more grim a struggle. It is a matter of life and death.
The law of nature, which also may be called the law of the jungle, says that every animal is in constant competition for food and safety, Those that fail to win perish from hunger or fall prey to their enemies. When we compete with each other, the two important things are to play fair and do our best. But in the world of nature it does not matter whether an animal is fair or not. He must compete to win, for if he does not win he will not survive.
This harsh rule of nature weeds out the failures from every generation of animals. Those that succeed must prove themselves fit. Only in one area were these rules not quite so strict. Australia is an island continent, cut off from the mayor land masses long ages ago. The big island broke off and drifted away when the mammals, or most of them, had reached the marsupial stage. They had progressed beyond the egg laying stage in which their unborn babies were left to the mercy of prowlers. Most mammal babies were tiny helpless creatures who had to be nursed for weeks and perhaps months in their mothers' pouches.
Most of the animals that drifted off on the floating continent were marsupials, or pouched animals. In the rest of the world, certain animals became meat eaters. They prowled and pounced with tooth and claw. Some creatures survived the competition because they were fast, some because they were smart and some because they had coats that made them almost invisible against their backgrounds. A great many different varieties of animal developed, but only a very few marsupials survived the law of the bungle.
In Australia the marsupials survived because no big meat eaters threatened them. Competition was not so tough. Most of them were vegetarians and their only problem was to find enough green stuff to eat. The koalas and the flying phalangers took to the tree tops. Mousy and ratty marsupials sought a living on the ground. The wallabies and the big kangaroos became browsers. They stood up and ate their food from shrubs and trees. The big kangaroo, seven feet tall and weighing 200 pounds had no enemies except man. He survived in Australia only because he did not have to fight for his life against big cats and other meat eaters.