VOA慢速英语2015 河马:非洲河流的生命力量

AS IT IS 2015-05-03 Hippos: The Life Force of African Rivers 河马:非洲河流的生命力量

The hippopotamus¹ is an animal very important to the health of Africa's rivers and lakes. Their dung, or solid waste, helps Africa’s aquatic² ecosystem³. But researchers warn that hippo populations are decreasing. They say that could damage ecosystems⁴.

The hippopotamus is the third-largest land mammal, after the elephant and rhinoceros⁵. Hippos spend as much as 16 hours a day in the water. They go on land at night to feed. They eat more than 200 kilograms of tropical grasses at each feeding. They return to the water where they release their waste.

Douglas McCauley is an assistant professor of several environmental and life sciences.  He and his team at the University of California, Santa Barbara, decided⁶ to study the waste of hippos.

“Well, we started looking at hippopotamus and realized that a big part of the story was their poop - was this vast amount of nutrients⁸ and energy that are moved across systems via their eating and their defecation.”

He says scientists are interested in how hippos cross the line of ecosystems. He says living in both the land and water worlds means hippos are important providers of nutrients.

“Because they're eating lots and lots of stuff on land and then taking that all back to the place where they rest in the water -- in lakes and rivers -- and then basically dunging that all out. And it turns out to be a huge amount of material and energy and nutrients of this sort of natural fertilizer that is moved across these boundaries.”

Every year, hippos provide over 60,000 kilograms of dung to African lakes and rivers.

Douglass McCauley says the dung is also used as a communication device. He says a more powerful male hippo will throw dung from its tail to a less powerful male.

The study also showed that some species of river fish need the dung in their diets. Mr. McCauley says some of the nutrients in the dung are the building materials of life. Some fish get the nutrients by eating the dung directly. Others feed on insects that eat the dung.

But as researchers learn more about the importance of hippos, there are fewer of them. Mr. McCauley says hippo numbers are dropping across sub-Saharan Africa. He says there has been a 10 to 20 percent drop in the past 10 years.

“And beyond how many there are they're in a lot fewer places. There are entire countries that have completely lost hippopotamus -- Egypt, for example.

Douglas McCauley says humans are responsible for most of the drop in the hippo population through hunting and habitat loss as human populations spread. He says animals often lose to humans in the competition for water.

“They have to have water. Well, guess what? Everybody else wants water.”

Mr. McCauley says careful thought must be given to the control of water, both for humans and wildlife. He says there should be enough water for all if it is dealt with intelligently. He said the future of humans, wildlife and ecosystems are closely tied together.

Words in This Story

dung – n. solid waste from an animal

ecosystem – n. everything that exists in a particular environment

tropical – adj. of, relating to, occurring in, or used in the tropics

vast – adj. very great in size or amount

poop – n. another word for dung

defecate – v. to pass solid waste from the body

nutrient⁷ –n. a substance that plants, animals and people need to live and grow

habitat – n. the place or type of place where a plant or animal naturally or normally lives or grows

1 hippopotamus   

n.河马

参考例句：

• The children enjoyed watching the hippopotamus wallowing in the mud.孩子们真喜观看河马在泥中打滚。
• A hippopotamus surfs the waves off the coast of Gabon.一头河马在加蓬的海岸附近冲浪。

2 aquatic   

adj.水生的，水栖的

参考例句：

• Aquatic sports include swimming and rowing.水上运动包括游泳和划船。
• We visited an aquatic city in Italy.我们在意大利访问过一个水上城市。

3 ecosystem   

n.生态系统

参考例句：

• This destroyed the ecosystem of the island.这样破坏了岛上的生态系统。
• We all have an interest in maintaining the integrity of the ecosystem.维持生态系统的完整是我们共同的利益。

4 ecosystems   

n.生态系统( ecosystem的名词复数 )

参考例句：

• There are highly sensitive and delicately balanced ecosystems in the forest. 森林里有高度敏感、灵敏平衡的各种生态系统。 来自《简明英汉词典》
• Madagascar's ecosystems range from rainforest to semi-desert. 马达加斯加生态系统类型多样，从雨林到半荒漠等不一而足。 来自辞典例句

5 rhinoceros   

n.犀牛

参考例句：

• The rhinoceros has one horn on its nose.犀牛鼻子上有一个角。
• The body of the rhinoceros likes a cattle and the head likes a triangle.犀牛的形体像牛，头呈三角形。

6 decided   

adj.决定了的，坚决的；明显的，明确的

参考例句：

• This gave them a decided advantage over their opponents.这使他们比对手具有明显的优势。
• There is a decided difference between British and Chinese way of greeting.英国人和中国人打招呼的方式有很明显的区别。

7 nutrient   

adj.营养的，滋养的；n.营养物，营养品

参考例句：

• Magnesium is the nutrient element in plant growth.镁是植物生长的营养要素。
• The roots transmit moisture and nutrient to the trunk and branches.根将水分和养料输送到干和枝。

8 nutrients   

n.（食品或化学品）营养物，营养品( nutrient的名词复数 )

参考例句：

• a lack of essential nutrients 基本营养的缺乏
• Nutrients are absorbed into the bloodstream. 营养素被吸收进血液。 来自《简明英汉词典》