河马对生态系统的意义

河马对生态系统的意义

A new study says the hippopotamus 1 is very important to the health of Africa’s rivers and lakes. That’s because hippos produce a key ingredient for aquatic 2 life -- and a lot of it. But researchers warn that hippo populations are on the decline and that could damage ecosystems 4.

一项新研究表明河马对于非洲河流湖泊的健康来说很重要，这是因为河马能为水生物制造大量的关键物质。但研究者警告称河马的数量正在下降，这将有损生态系统。

The mighty 5 hippopotamus is the third largest land mammal following the elephant and rhinoceros 6. Its name is derived 7 from the ancient Greek for river horse. Hippos spend up to 16 hours a day in the water and venture on to land at night to feed. They eat tropical grasses, more than 200 kilograms per meal. And what goes in must come out. And there is the magic ingredient for Africa’s aquatic ecosystems – dung.

庞大的河马是仅次于大象和犀牛的第三大陆生哺乳动物，其名字来源于古代希腊的河马。河马一天要在水中16小时，然后晚上冒险上岸觅食。它们吃大量的热带杂草，每顿要吃200多公斤。吃下去就要排泄，这就是非洲水生态系统中的神奇成分—粪便。

Douglas McCauley and his colleagues decided 8 to study it.

道格拉斯·麦考利和同事们决定研究河马的粪便。

“Well, we started looking at hippopotamus and realized that a big part of the story was their poop – was this vast amount of nutrients 10 and energy that are moved across systems via their eating and their defecation,” he said.

“我们研究河马时意识到它们的粪便非常重要，有大量的营养物质和能量通过它们的饮食和排泄来在生态系统内循环。”

McCauley is an assistant professor of ecology, evolution and marine 11 biology at the University of California Santa Barbara. He said hippos cross the boundaries of ecosystems.

麦考利是加州大学圣巴巴拉校区生态、演化和海洋生物学助理教授，他说河马参与了不同的生态系统。

“Transiting between two different domains 12 – between land, the terrestrial world, and then the aquatic world – means that there are also these important nutrient 9 vectors. Because their 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 when you start crunching 13 the numbers to be a huge amount of material and energy and nutrients of this sort of natural fertilizer that is moved across these boundaries,” he said.

“河马在两个不同的领域—陆上和水中进行活动，这意味这些重要的营养物质也在水陆之间传输，因为它们吃大量的陆上食物，然后在水中休息时带到水中，基本上是在河水和湖中将粪便排泄出来。所以如果进行计算，就会发现这种天然粪便中有非常大体量的物质、能量和营养物质在不同的系统间运输。”

So, each hippo contributes, if you will, over 60,000 kilograms of dung to African lakes and rivers every year.

所以，每头河马每年向非洲的河流湖泊中排泄超过6万公斤的粪便。

“It’s a big animal,” he said, “We’re talking about an animal that’s about 4,000 to 8,000 pounds. So, it’s got a big appetite. When you look across the entire continent and our estimate of how many hippos we now have in sub-Saharan Africa that comes out to millions of kilograms.”

“这种动物很庞大，有4000到8000磅，所以它们胃口很大。所以着眼于整个非洲大陆，我们估计现在撒哈拉南部非洲的河马能制造数百万公民的粪便。”

So, by now you understand it’s a tremendous amount of dung. But did you know that hippo dung looks like straw?

这样现在你就明白这些粪便有多少了，但你知道吗？河马的粪便看上去很像干草吗？

“That’s right. So, they are mostly feeding on grass, sort of a straw-like grass. In fact, a lot of African grasses are used as straw and forage 14 for cattle in places like America. So, they have these wonderfully well-developed lips that they use like a lawnmower to go across these short grass lawns that they actually manicure. And they keep them short because it seems to keep this resource accessible just to them,” said McCauley.

“那就对了，河马主要以杂草为生，有点像干草的那种草。事实上，美国等地方会使用很多非洲杂草做为干草和饲料。所以，它们的嘴唇很发达，在吃短草坪时很像除草机那样修剪杂草，它们让杂草保持啃得很短，因为似乎只有它们自己能吃到这么短的草。”

McCauley said it’s even used as a communication device.

麦考利说河马甚至使用粪便来作为通讯工具。

“They actually use dung as a kind of signal amongst themselves. So, a male animal will dung at a sub-dominant male. They actually fling it back and forth 15 with their paddle-like tail.”

“它们使用粪便作为自己族群中的信号，所以，一头雄河马会在地位低的雄河马身上排便，它们会用船桨似的尾巴把粪便抛来抛去。”

But the really important thing about hippo dung is its place in the food chain.

但河马粪便真正重要的意义在于其在食物链中的地位。

“Well, there’s a lot of good stuff in dung. There’s a lot of nitrogen, carbon, even a bit of phosphorus. And some of these nutrients can be limiting in river systems. These are sort of the building blocks of life in some cases. So it really is injecting more of this food into these rivers. And a lot of the animals it seems in the rivers are quite happy to receive it. Some of them eat it up directly and some consumers, like fish, will eat insects that started their lives feeding on dung,” he said.

“粪便里有很多好东西，有大量的氮、碳、甚至还有磷，一些营养物质在河流系统中很有限，在一些情况下它们是构成生命的元素。所以河马是在向河流排出大量的食物，而且似乎河中的很多动物都很喜欢这些粪便，有的动物直接吃粪便，像鱼类这样的捕食者会以食用粪便的昆虫为生。”

McCauley actually described it as a life force in Africa’s rivers and lakes. But he said if the water flow is too low, the dung could overwhelm the ecosystem 3 and be a pollutant 16. Too much water and its value is diluted 17.

麦考利称河马粪便是非洲河流湖泊的生命物质，但他说如果河水流动太慢，粪便就会破坏生态系统，就成了污染物质，如果水太多，粪便的价值就会被稀释。

But as researchers learn more about the importance of hippos, there are fewer of them.

但就在研究者对河马的重要性有更多了解时，河马的数量却在减少。

“Hippos are declining across sub-Saharan Africa. In the past decade or so, we’ve seen about a 10 to 20 percent decline in their numbers. 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. Hippos used to be an iconic god. It was the god of birth in Egypt. You see the hippo god. It’s a goddess turning up on amulets 18 and wands and swords,” he said.

“整个撒哈拉南部非洲的河马数量都在减少，在过去10来年间，我们看到河马数量减少了10%到20%。除了整体数量减少外，它们的栖息地数量也在减少。有的国家已经完全没有了河马，比如埃及。河马过去被当做偶像崇拜的神，在埃及河马是出生之神，你能看到有河马神，护身符、权杖和刀剑上都有这种女神。”

McCauley said humans are responsible for most of the decline in the hippo population through hunting and habitat loss as human populations spread.

麦考利说人类要对河马数量减少负很大责任，随着人口的流动，人类的狩猎和占领栖息地导致河马减少。

“They have to have water. Well, guess what? Everybody else wants water. And it’s really unfortunate if you’ve tied your fate to water because when you compete with humans for water you often lose. So, people want water from rivers and lakes for building out cities – for helping 19 to cool turbines– or damming rivers,” he said.

“河马一定得有水，你猜怎么着？大家都需要水，如果你的命运与水有关，那就很不幸，因为你跟人类竞争时通常会输。人们想获得河流湖泊里的水来建造城市，来冷却涡轮或在河流上筑坝。”

It’s estimated hippos kill about 3,000 people a year. The animals may attack, for example, if people get too near a mother and calf 20.

据估计河马每年导致大约3000人丧生，比如，如果人距离母河马和河马幼崽太近，人类就会被袭击。

McCauley said careful thought must be given to the management of water, both for humans and wildlife. He says if managed intelligently, there should be plenty of water to go around, adding that the fates of humans, wildlife and ecosystems are closely tied together.

麦考利说必须认真管理水，无论是为人类还是为野生物。他说如果管理得当，应该有大量的水可供使用，因为人类、野生物和生态系统的命运是密切关联的。

The study appeared in the journal Ecosphere.

这份研究发表在期刊《生物圈》上。