英语听力：自然百科 野性俄罗斯之西伯利亚 Siberia—12
时间：2014-05-22 08:13:25
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（单词翻译）
After spending a year or so as larvae1 under water, they transform into winged adults and take to the skies. The millions of tiny flies attract far bigger animals. As they hold a mass mating orgy along the banks of the lake, brown bears come to feed on this fleeting2 feast of protein.
The flies may only live for a week, so must rush to lay eggs on the water before dying. And for ten days or so, bears search them out, dead or alive.
They can eat up to 40 kilos of food a day and flies make a pleasant addition to their mainly
vegetarian3 diet. Many are attracted by this short-lived feast. But even with this abundance, a smaller bear must
defer4 to a bigger one.
While animal life flourishes in the woods around Baikal Lake, a different population of creatures thrives in the middle. Just 1.5 kilometers from the nearest shore lies the island of Olkhon. This is the largest of Baikal’s 25 islands – about the same size as Dubai.
Snakes have managed to cross the water to populate Olkhon Island. This one, a Dione’s ratsnake, isn’t venomous. But they keep the
rodent5 population in check.
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