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Trevor says the thunderbirds’ vegetarian diet might partly explain their size.
特雷弗认为，雷鸟食素的饮食习惯可能是它们体型庞大的部分原因。
You can get big; you can have a big gut. And then you can eat a lot of rubbish.
你的体型会变大; 你的胃会变得很大。你可以吃进很多劣质食物。
So if you can ingest a lot of low-quality food, then that is one way of living in an environment.
如果你可以摄入大量品质低劣的食物，那也是在环境中生存的一种方式。
Their big body probably helped them in other ways, too.
雷鸟庞大的身体可能也在其他方面帮助了它们。
Here’s Anusuya again.
以下是金萨米的观点。
Their body size probably evolves in the context of what else is around at the time.
它们的体型可能是根据当时周围的环境而进化的。
In Australia, there were these thylacines. There are these marsupial lions, and I think a big body size would have enabled them to escape predation.
澳大利亚有袋狼，也有袋狮，我认为雷鸟巨大的体型可以让它们逃脱被捕食的命运。
They’re just too big to eat.
雷鸟体型太大了，没法吃。
Yeah. Or otherwise it’s too much of trouble to deal with them. You know, you rather go after something that’s smaller, that’s not going to harm you.
是的。处理雷鸟实在太麻烦了。它们宁愿去找一些体型更小的动物，也不愿伤害雷鸟。
Because, I think, you know, we know ostriches certainly are not predators, but an ostrich can do pretty serious damage to, to any animal that attacks it just by kicking.
因为，我们当然知道鸵鸟不是捕食者，但鸵鸟可以对任何攻击它的动物造成严重伤害。
And if they’re related to geese, I mean, we all know how terrifying geese can be.
如果雷鸟是鹅的近亲，我们都知道鹅有多可怕。
Yes. You know, I had a friend earlier this year that was attacked by a goose, and you’re not going to believe this, but literally, she had to be hospitalized because this goose attacked out of nowhere.
是的。年初，我有个朋友被一只鹅袭击了，你不会相信，实际上，因为这个不知道从哪里冒出来的鹅袭击了我朋友，她不得不住院。
Just imagine if that goose was, you know, 1,300 pounds.
想象一下，如果那只鹅有1300磅重。
Exactly. Exactly.
是的，正是如此。
But how did they grow so big? That’s something Anusuya wanted to understand.
但它们是怎么长这么大的呢? 这正是金萨米想要了解的。
To drill down on that question, she took a very thin section of a thunderbird bone and looked at it under the microscope.
为了深入研究这个问题，她从雷鸟的骨头上取了一小部分，放在显微镜下观察。
And this is fascinating because it tells us about the way in which the bone was deposited. So it tells us about the rates of growth.
这很有趣，因为这展示了雷鸟骨头沉积的方式以及骨头生长的速度。
Bones have rings that correspond to growth. Like tree rings…
骨头上有与生长相对应的骨轮。与树的年轮一样……
Where you have a white band that is growth during the favorable season, and then you have a growth line that indicates growth stopped for a period of time, and then afterward, it resumes.
这里有一个白色条纹，表示生长在适宜的季节里，之后出现了一条生长线，表示生长停止了一段时间，之后又恢复了生长。
So just like tree rings, you can count the number of rings, and you can work out the age of the animal, and you can work out how long it took for an animal to grow to an adult body size.
就像树木的年轮一样，你可以数年轮的圈数计算树龄，同样，你也可以计算出雷鸟的年龄，你可以计算出雷鸟长到成年体型需要多长时间。
This bone ring method is a feather in Anusuya’s cap—she developed it when she was just a fledgling Ph.D. student working on dinosaurs.
这种骨轮法是金萨米的得意成就——当她还是一名研究恐龙的初出茅庐的博士生时，她就发明了这种方法。
And when she applied the method to this giant thunderbird, she found ...
当她把这种方法应用到这只巨大的雷鸟身上时，她发现…...
These birds lived life in the slow lane.
这些鸟生活节奏很慢。
We can find growth cycles in the bones that suggest that they took about 15 years to reach an adult body size.
我们可以发现生长骨环，这表明雷鸟花了大约15年的时间才达到成年体型。
And this is really a long time, compared to modern birds that grow up very quickly.
与现代生长得很快的鸟类相比，这真的是很长的一段时间。
And it took them years to have babies, too, the data suggest.
数据显示，雷鸟要花很多年才能产下幼崽。
Anusuya and Trevor say that gives us some insight, into why these birds don’t exist today.
金萨米和特雷弗表示，关于为什么这些鸟今天不存在了，这给了我们一些启发。
