That's right, animals. Scientists have begun to understand what farmers have known for thousands of years. Animals often seem to know in advance that an earthquake is coming, and they show their fear by acting in strange ways. Before a Chinese quake in 1975, snakes awoke from their winter sleep early only to freeze to death in the cold air. Cows broke their halters(缰绳) and tried to escape.Chickens refused to enter their cage. All of this unusual behavior, as well as physical changes in the earth, warned Chinese scientists of the coming quake. They moved people away from the danger zone and saved thousands of lives.

　　One task for scientists today is to learn exactly which types of animal behavior predict quakes. It's not an easy job. First of all, not every animal reacts to the danger of an earthquake. Just before a California quake in 1977, for example, an Arabian horse became very nervous and tried to break out of his enclosure. The Australian horse next to him, however, remained perfectly calm. It's also difficult at times to tell the difference between normal animal restlessness and “earthquake nerves”．A zoo keeper once called earthquake researchers, saying that his cougar had been acting strangely. It turned out that the cat had an upset stomach.

　　A second task for scientists is to find out exactly what kind of warnings the animals receive. They know that animals sense far more of the world than humans do. Many animals can see, hear, and smell things that people do not even notice. Some can sense tiny changes in air pressure, gravity, or the magnetism of the earth. This extra sense probably helps animals predict quakes.

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