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科学美国人60秒 SSS What's a Narwhal's Tusk For?

时间:2020-05-06 08:35:29

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(单词翻译)

Although the tusk1 can be a weapon, the variation in tusk length among animals of similar body size points to it being primarily a mating status signal.

Full Transcript2 

Deep beneath the frozen surface of the Arctic swims a sea unicorn3. In reality, it’s a whale with a spiral tusk sprouting4 from its head—the narwhal. Biologists have long debated the purpose of male narwhals’ tusks5. The tusk, like those of elephants, are actually elongated6 teeth. And since narwhals are usually below the sea ice, it’s tough to see how they use their tusk.

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

Arizona State University evolutionary7 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.

“One of the main trends that has been documented in over 100 different animals is disproportionate growth. We call that hyperallometry. 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.”

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

“The majority of them are from the Inuit hunt. So the Inuit have been killing8 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.”

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. [Zackary A. Graham et al., The longer the better: Evidence that narwhal tusks are sexually selected]

The top tusks thus appear to be like a billboard9 that shouts, “Look at me. I’m the biggest.” After all, only the strongest, best fed individuals can afford to produce such an ostentatious ornament10. Of course, tusks can do more than just say, “Hey, how you doin’?”

“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.”

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 diversify11 than those without.

“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.”

—Jason G. Goldman

[The above text is a transcript of this podcast.]


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1 tusk KlRww     
n.獠牙,长牙,象牙
参考例句:
  • The wild boar had its tusk sunk deeply into a tree and howled desperately.野猪的獠牙陷在了树里,绝望地嗥叫着。
  • A huge tusk decorated the wall of his study.他书房的墙上装饰着一支巨大的象牙。
2 transcript JgpzUp     
n.抄本,誊本,副本,肄业证书
参考例句:
  • A transcript of the tapes was presented as evidence in court.一份录音带的文字本作为证据被呈交法庭。
  • They wouldn't let me have a transcript of the interview.他们拒绝给我一份采访的文字整理稿。
3 unicorn Ak7wK     
n.(传说中的)独角兽
参考例句:
  • The unicorn is an imaginary beast.独角兽是幻想出来的动物。
  • I believe unicorn was once living in the world.我相信独角兽曾经生活在这个世界。
4 sprouting c8222ee91acc6d4059c7ab09c0d8d74e     
v.发芽( sprout的现在分词 );抽芽;出现;(使)涌现出
参考例句:
  • new leaves sprouting from the trees 树上长出的新叶
  • They were putting fresh earth around sprouting potato stalks. 他们在往绽出新芽的土豆秧周围培新土。 来自名作英译部分
5 tusks d5d7831c760a0f8d3440bcb966006e8c     
n.(象等动物的)长牙( tusk的名词复数 );獠牙;尖形物;尖头
参考例句:
  • The elephants are poached for their tusks. 为获取象牙而偷猎大象。
  • Elephant tusks, monkey tails and salt were used in some parts of Africa. 非洲的一些地区则使用象牙、猴尾和盐。 来自英语晨读30分(高一)
6 elongated 6a3aeff7c3bf903f4176b42850937718     
v.延长,加长( elongate的过去式和过去分词 )
参考例句:
  • Modigliani's women have strangely elongated faces. 莫迪里阿尼画中的妇女都长着奇长无比的脸。
  • A piece of rubber can be elongated by streching. 一块橡皮可以拉长。 来自《用法词典》
7 evolutionary Ctqz7m     
adj.进化的;演化的,演变的;[生]进化论的
参考例句:
  • Life has its own evolutionary process.生命有其自身的进化过程。
  • These are fascinating questions to be resolved by the evolutionary studies of plants.这些十分吸引人的问题将在研究植物进化过程中得以解决。
8 killing kpBziQ     
n.巨额利润;突然赚大钱,发大财
参考例句:
  • Investors are set to make a killing from the sell-off.投资者准备清仓以便大赚一笔。
  • Last week my brother made a killing on Wall Street.上个周我兄弟在华尔街赚了一大笔。
9 billboard Ttrzj     
n.布告板,揭示栏,广告牌
参考例句:
  • He ploughed his energies into his father's billboard business.他把精力投入到父亲的广告牌业务中。
  • Billboard spreads will be simpler and more eye-catching.广告牌广告会比较简单且更引人注目。
10 ornament u4czn     
v.装饰,美化;n.装饰,装饰物
参考例句:
  • The flowers were put on the table for ornament.花放在桌子上做装饰用。
  • She wears a crystal ornament on her chest.她的前胸戴了一个水晶饰品。
11 diversify m8gyt     
v.(使)不同,(使)变得多样化
参考例句:
  • Our company is trying to diversify.我们公司正力图往多样化方面发展。
  • Hills and woods diversify the landscape.山陵和树木点缀景色。

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