托福听力短文 II-12-1

(WA) If you liked the colorful animals we just saw, you're going to love these next animals. Frogs. You might not normally think of frogs as being colorful, but these frogs definitely are. They are the dart-poison frogs of Central and South America. Look at their striking colors --- often yellow with black stripes or deep blue with black spots.

Beyond being nice to look at, these markings have a purpose. They warn predators¹ that these frogs are poisonous. When threatened, these frogs secrete² a substance through their skin that would easily kill whatever animal might try to eat them. Their bright colors communicate this, and so most animals tend not to hunt them.

Now, speaking of hunting, for centuries these frogs were sought after by hunters. As you might think, the hunters didn't want to eat the frogs, but rather, they captured them for their poison. They would add the poison to the tips of their hunting arrows --- of course, nowadays most hunters use guns.

These days dart-poison frogs are of less interest to hunters than to medical researchers. Researchers believe that they can make new heart medicine from the poison, because it acts as a stimulant³ on the body's nervous system. Researchers think they could use it to stimulate⁴ a weak heart.

There is, however, a problem with doing research on these frogs. Those that are caught in the wind will produce their poison until they die. However, those that are born in captivity⁵, like the ones you see here, will not produce any poison at all.

1 predators   

n.食肉动物( predator的名词复数 )；奴役他人者（尤指在财务或性关系方面）

参考例句：

• birds and their earthbound predators 鸟和地面上捕食它们的动物
• The eyes of predators are highly sensitive to the slightest movement. 捕食性动物的眼睛能感觉到最细小的动静。 来自《简明英汉词典》

2 secrete   

vt.分泌；隐匿，使隐秘

参考例句：

• The pores of your body secrete sweat.身上的毛孔分泌汗液。
• Squirrels secrete a supply of nuts for winter.松鼠为准备过冬而藏坚果。

3 stimulant   

n.刺激物，兴奋剂

参考例句：

• It is used in medicine for its stimulant quality.由于它有兴奋剂的特性而被应用于医学。
• Musk is used for perfume and stimulant.麝香可以用作香料和兴奋剂。

4 stimulate   

vt.刺激，使兴奋；激励，使…振奋

参考例句：

• Your encouragement will stimulate me to further efforts.你的鼓励会激发我进一步努力。
• Success will stimulate the people for fresh efforts.成功能鼓舞人们去作新的努力。

5 captivity   

n.囚禁；被俘；束缚

参考例句：

• A zoo is a place where live animals are kept in captivity for the public to see.动物园是圈养动物以供公众观看的场所。
• He was held in captivity for three years.他被囚禁叁年。