科学美国人60秒：独角鲸的长牙有什么用？

　　What's a Narwhal's Tusk For?

　　独角鲸的长牙有什么用?

　　Deep beneath the frozen surface of the Arctic swims a sea unicorn. In reality, it's a whale with a spiral tusk sprouting from its head—the narwhal. Biologists have long debated the purpose of male narwhals' tusks. The tusk, like those of elephants, are actually elongated teeth. And since narwhals are usually below the sea ice, it's tough to see they use their tusk.

　　在北极的冰面下，一只海麒麟正在游动。事实上，这是一只头上长着螺旋状獠牙的鲸鱼——独角鲸。生物学家对雄性独角鲸长牙争论已久。它的牙和大象的一样，实际上是细长的牙齿。由于独角鲸通常生活在海冰下面，所以很难看到它们使用长牙。

　　"It turns out we don't know pretty much anything about them, because they're impossible to study in the wild."

　　“事实证明，我们对它们知之甚少，因为在野外研究是不可能的。”

　　

　　Arizona State University evolutionary biology graduate student Zackary Graham. He wondered if the males’ tusks were a sign of status as a potential reproductive partner. Comparing tusk size to the whales' overall body size could provide evidence.

　　亚利桑那州立大学进化生物学研究生扎卡里·格雷厄姆说道。他想知道雄鲸的长牙是否是潜在生殖伙伴身份的象征。将象牙的大小与鲸鱼的整体体型进行比较可以提供证据。

　　"One of the main trends that has been documented in over one hundred different animals is disproportionate growth. We call that hyper-allometry. All that means is that the sexual trait is growing disproportionately compared to the rest of the body. So it's not like the biggest narwhal is just a scaled up version of a baby narwhal. What we see is that the tusk is disproportionately long…and then we also see that there is intensive variation."

　　“在一百多种不同的动物身上记录的主要趋势之一是不成比例的增长。我们称之为超光速测量。所有这一切意味着，性特征与身体的其他部分是不成比例地增长。不像最大的独角鲸只是小独角鲸的放大版。我们看到的是，牙长得不成比例，然后还有强烈的变异。”

　　So Graham and his team turned to measurements collected from 250 adult males over 35 years.

　　所以格雷厄姆和团队转向了收集了250名成年男性超过35年的测量数据。

　　"The majority of them are from the Inuit hunt. So the Inuit have been killing narwhals for thousands and thousands of years. And any time they do that, the Greenland Institute of Natural Resources asks them to collect a bunch of data."

　　“他们中的大多数来自因纽特狩猎。因此，数千年来，因纽特人一直在捕杀独角鲸。每次他们这么做的时候，格陵兰自然资源研究所都会要求他们收集大量数据。”

　　Turns out the length of the tusks can vary widely even for males the same size, ranging from a foot and a half to more than eight feet. The finding is in the journal Biology Letters.

　　结果表明，即使是同样大小的雄性，牙的长度也会有很大的差异，从1.5英尺到超过8英尺不等。研究i结果发表在《生物学快报》杂志上。

　　The top tusks thus appear to be like a billboard that shouts, "Look at me, I'm the biggest." After all, only the strongest, best fed individuals can afford to produce such an ostentatious ornament. Of course, tusks can do more than just say “Hey. How you doin’?”

　　上面的牙看起来就像一块广告牌，上面写着:“看看我，我是最大的。”毕竟，只有最强壮、吃得最饱的人才有这种招摇的装饰品。当然，长牙能做的不仅仅是说“嘿，你好吗”。

　　"But the fact that these narwhals always have these scars on them makes us think that it's likely a communication structure that also functions as a weapon."

　　但事实是，这些独角鲸身上总是有些伤疤，这让我们认为，这可能是一种沟通结构，同时也是一种武器。”

　　For Graham, there’s also a larger issue. Some evolutionary biologists have recently proposed a hypothesis that groups of animals with elaborate sexual signals are more likely to speciate and diversify than those without.

　　对格雷厄姆来说，还有一个更大的问题。一些进化生物学家最近提出了一种假设，拥有复杂性信号的动物群体比那些没有性信号的更有可能形成物种并多样化。

　　"We know the world is changing around us more than ever, so understanding how and why species are going to be able to adapt and deal with this is key if we are to protect and manage the species we have on Earth today."

　　“我们知道，周围的世界正在发生前所未有的变化，因此，如果我们要保护和管理今天在地球上拥有的物种，了解物种如何以及为什么能够适应和应对变化是关键。”