EigoPro 準2級プラス 読解 — Nature's Travellers

Nature's Travellers Every year, countless animals make journeys that would astonish any human traveller. Birds fly thousands of kilometres between continents. Sea turtles cross entire oceans to lay their eggs on the very beach where they were born. Somehow, without maps or signs, these creatures find their way. For a long time, how they did this was a complete mystery. Reading the Sky One of the first clues scientists found was that many animals use the sky. Some birds appear to navigate by the position of the sun during the day and by the stars at night. Young birds raised indoors, who had never seen the night sky, became confused on their first journeys — strong evidence that they normally learn from the stars above them. A Sense We Lack Even more surprising was the discovery that some animals can sense the Earth's magnetic field — the same force that makes a compass needle point north. Humans cannot feel this force at all, but for certain birds, turtles, and even some insects, it seems to act like an invisible map. Using it, they can tell which direction they are heading and roughly where on Earth they are. Many Tools at Once Researchers now believe that most travelling animals do not rely on a single method. Instead, they combine several: the sun, the stars, the magnetic field, and even smells and landmarks along the way. If one tool fails — for example, when the sky is covered by clouds — they can switch to another. This combination makes their navigation remarkably reliable. Still Learning Despite decades of study, scientists admit there is much they still do not understand. As one researcher said, "We have learned that animals are far better navigators than we are. What we have not yet learned is exactly how they do it."

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