经济学人下载:海豹如何享用它的午餐

Science and technology
科学技术

How leopard seals lunch
海豹如何享用它的午餐

Suck, swish, gulp
吸，吮，咽

Eating big and little
大小通吃

JUST about every place on the planet has a predator at the top of the food web.
地球上每个地方都有一个处于食物网顶端的捕食者。

The African savannahs have the lion, the jungles of Asia the tiger and the arctic tundra the polar bear.
比如非洲大草原上的狮子，亚洲丛林里的老虎以及北极冻原上的北极熊。

In the Antarctic it is the leopard seals who dominate as voracious hunters of penguins and other seal species.
而南极的霸主则是那些贪婪地捕食着企鹅和其他海豹种群的豹海豹。

But a new study examining their feeding habits led by David Hocking of Monash University in Australia, has revealed something unusual:
但是一个验证豹海豹进食习惯的新研究显示了一些不寻常的东西：

how leopard seals use an efficient filter-feeding system to eat near the bottom of the food chain too.
那就是豹海豹如何利用一个高效的食物过滤系统同时享用靠近食物链底端的生物。来自澳大利亚蒙纳什大学的大卫霍金是此项研究的负责人。

Researchers have long known that a sizeable portion of the seals’ diet is made up of krill.
研究者们很早就知道在豹海豹的食谱中一大部分是由磷虾组成。

But exactly how they consume these tiny crustaceans has been a mystery as the seals’ mouths have large sharp teeth that seemed utterly inappropriate for capturing them.
但是由于豹海豹嘴里的尖牙似乎完全不适合捕捉这些磷虾，从而它们是如何享用这些微小的甲壳类生物便成了一个迷。

Some researchers have theorised that the seals might suck water into their mouths and swish it past their closed teeth to capture krill.
一些研究者们从理论角度分析豹海豹也许可以通过先入吸海水再闭紧牙齿将海水吐出的筛选法捕捉磷虾。

But such behaviour depends upon leopard seals being able to suck up food from water, a specialised feeding behaviour that is rarely seen in top predators.
但是完成这些动作需要豹海豹具备从海水中吸吮食物的能力，而这种特定的进食行为在位于食物链顶端的捕食者身上并不常见。

Keen to explore this, Mr Hocking turned his attention towards Casey and Sabine, two leopard seals at the Taronga Zoo in Sydney.
热衷于探索这一问题的霍金先生将注意力转向了凯西和萨宾这两只悉尼塔龙加动物园的豹海豹身上。

He and his colleagues designed a clear plastic box with thin tubes in which fish could be placed.
他和同事们设计了一种透明的塑料盒子，里面安装了可以盛放鱼的浅的管道。

The seals could not get at them with their teeth, and instead sucked the fish right out of the tubes.
豹海豹无法用它的牙齿来取食这些鱼，而是从管道中把它们吸出来。

Moments later, the team saw clouds of murky water and bubbles being expelled from the sides of the seals’ mouths.
过了一会，研究小组发现一团一团的浑浊的水体和泡沫从豹海豹的嘴里喷出。

This, they realised, was a filter-feeding system in action.
研究者们意识到，这表示一套进食过滤系统正在工作。

In examining the wear on the teeth of skulls from wild leopard seals, Mr Hocking was able to work out which teeth the seals were using to filter out tiny prey.
在检查野生豹海豹颅骨上牙齿的磨损度时，霍金先生弄明白了豹海豹是用哪些牙齿来过滤出微小猎物的。

He found extensive abrasions on canines and incisors, the sharp teeth at the front of their mouths.
他发现位于口腔前端的那些锋利的犬齿和门齿上存在大面积磨损的情况。

This, Mr Hocking points out in Polar Biology, indicates that these teeth are used to chomp penguins and other seals.
霍金先生在《极地生物》杂志上指出，这表明豹海豹利用这些牙齿来撕咬企鹅和其他海豹。

But since there is no such wear on the sharp and delicate postcanines, he believes that although these triangular rear teeth look fierce, when closed they form a sieve that is the perfect size for filtering.
但是，由于在锋利而精致的犬齿后齿上并没有发现磨损的情况，他认为尽管这些三角形的后槽牙看上去非常凶狠，但是当咬合时，它们可以充当一个对于过滤事物来说其尺寸可谓完美的筛子。

Ideal dentistry, if you like, for a mixed diet.
如果你乐意，这是一套进行混合膳食的理想的牙科学。