他们曾观察过这些动物的习性。
They had observed regularities in the behaviour of the animals.
游客可以观察大熊猫的自然习性，还可以帮助研究人员饲养并与这些美丽濒临灭绝的动物玩耍。
Tourists can observe pandas in their natural habitat and can also help researchers feed and play with these beautiful and threatened animals.
在1959年，他到中非与这些野生动物住在一起，观察它们的习性。
In nineteen fifty-nine, he moved to Central Africa to live in the wild with the animals and observe their behavior.
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