更多文章请关注微信公众号：英文外刊双语阅读
Why are whales so big? One answer is simply that they can be. The size of land animals is constrained in part by their need to support themselves against the force of gravity. Marine creatures have that support provided free, by the medium they live in.
为什么鲸鱼的体型如此庞大？有一个答案很简单，它们就是能长到这么大。陆地动物体型受限的部分原因是因为它们需要依靠自身对抗地心引力。海洋生物可以通过它们生活的环境为媒介免费获得这种支持。
Even so, what is possible is not always sensible. Resources put into growth are unavailable for reproduction. Given that whales can and do become big, however, a second question arises: what, if anything, stops them being even bigger? Jeremy Goldbogen of Stanford University and his colleagues suspect that the answers to both questions are related to the animals' food supply.
即便如此，可能的事情并不总是明智的。投入生长的资源无法再生产。鉴于鲸鱼可以且确实庞大，第二个问题就来了：如果有的话，有什么可以阻止它们变得更大？斯坦福大学的Jeremy Goldbogen和他的同事怀疑两个问题的答案和动物的食物供应有关。
And, as they describe in a paper in Science, they have gathered data that illuminatehow this might work. Broadly, big whales come in two varieties. Toothed whales, such as sperm whales, hunt individual prey.
正如他们在《Science》杂志中发表的一篇论文所述，他们收集了数据，阐明了可能的运作方式。总的来说，大鲸鱼有两种。齿鲸，如抹香鲸，捕食单个猎物。
Baleen whales suck in mouthfuls of water and extract small organisms such as krill, using fibrous buccal filters. The biggest whales of all (blue, humpback and so on) are baleen whales. This might be viewed as paradoxical, because on land, as predators get bigger, so do their individual prey.
须鲸，用纤维状的口腔过滤器吸入大量的水，并从磷虾等小生物中吸取营养。所有鲸鱼中最大的鲸类（蓝鲸、座头鲸等）是须鲸。这或许被认为是很矛盾的，因为在陆地上，捕食者越大，它们的猎物也越大。
Both toothed and baleen whales often hunt by diving deep—prey being more abundant at depth. To do this they have to hold their breath, which limits how long they can stay underwater. One explanation of giantism in whales is that because bigger whales can hold their breath longer, they can spend more time hunting.
齿鲸和须鲸通常都潜入深海捕食，因为深海里的猎物更多。为了去深海捕食，它们会屏住呼吸，这就限制了它们在深水中停留的时间。鲸鱼巨大体型的解释之一是因为体型越大，屏息时间越长，这样它们就能花更长时间在深海捕食。
But that will only hold good as long as the extra time is spent productively. Dr Goldbogen and his team attached water-and-pressure-proof data-recording tags to a range of both toothed and baleen cetaceans, to see what they got up to on their hunting dives.
对于鲸鱼巨型化的一种解释是，体型越大的鲸鱼屏住呼吸的时间越长，它们才有更多的时间去捕猎。但只有在额外的时间能有效捕猎的情况下，这一理论才能成立。戈德伯格和他的团队将防水且耐压的数据记录仪分别安置在齿鲸和须鲸身上，从而记录它们在潜水时的行为。
Toothed whales, they found, are living on the edge, size-wise. The number of individualprey they are able to chase and capture in a single dive is just enough to sustain animals of their size.
他们发现，齿鲸就体型而言已经到达了极限。它们每次下潜能够捕捉到的单个猎物的数量仅够维持它们现有的体型。
By contrast, the baleen whales the researchers looked at, once they have encountered a shoal of prey, are in nutritional nirvana. A single lunge by a large rorqual, they reckon, can capture ten times as much food as the largest individual prey taken by toothed whales.
相比之下，研究人员观察到，须鲸一旦遇到了一群猎物，就仿佛进入了充满营养的天堂。它们估计，一只大须鲸一次潜水所能捕获食物的量是齿鲸所能捕获到的最大单个猎物的十倍。
Toothed whales thus do seem to have hit some sort of size limit. Perhaps, though, baleen whales might continue to evolve and get bigger still. The blue whale is, at the moment, the largest animal, extant or extinct, known to have lived. Might its descendants be larger yet?
因此，齿鲸似乎确实到了其体型的极限。不过，须鲸或许会继续进化，从而变得更大。目前，蓝鲸是目前已知的（现存的或已灭绝的）体型最大的动物。它的后代会变得更大吗？
重点单词：
prey [preɪ] n.n.牺牲者；被掠食者，猎物
illuminate [ɪ'lumɪnet] v.照亮，照明;阐明，说明
paradoxical [,pærə'dɑksɪkl] adj. 矛盾的;反常的,荒谬的;反论的
更多文章请关注微信公众号：英文外刊双语阅读
閱讀更多 英文外刊雙語閱讀 的文章
