英语听力：自然百科 野性俄罗斯之西伯利亚 Siberia—12

 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.

1 larvae   

n.幼虫

参考例句：

• Larvae are parasitic on sheep.幼虫寄生在绵羊的身上。
• The larvae prey upon small aphids.这种幼虫以小蚜虫为食。

2 fleeting   

adj.短暂的，飞逝的

参考例句：

• The girls caught only a fleeting glimpse of the driver.女孩们只匆匆瞥了一眼司机。
• Knowing the life fleeting,she set herself to enjoy if as best as she could.她知道这种日子转瞬即逝，于是让自已尽情地享受。

3 vegetarian   

n.素食者；adj.素食的

参考例句：

• She got used gradually to the vegetarian diet.她逐渐习惯吃素食。
• I didn't realize you were a vegetarian.我不知道你是个素食者。

4 defer   

vt.推迟，拖延；vi.(to)遵从，听从，服从

参考例句：

• We wish to defer our decision until next week.我们希望推迟到下星期再作出决定。
• We will defer to whatever the committee decides.我们遵从委员会作出的任何决定。

5 rodent   

n.啮齿动物；adj.啮齿目的

参考例句：

• When there is a full moon,this nocturnal rodent is careful to stay in its burrow.月圆之夜，这种夜间活动的啮齿类动物会小心地呆在地洞里不出来。
• This small rodent can scoop out a long,narrow tunnel in a very short time.这种小啮齿动物能在很短的时间里挖出一条又长又窄的地道来。