This is Scientific American — 60-Second Science. I'm Jason G. Goldman.
Got a minute?
There's a well-known conspiracy of ravens—that's what you call a group of ravens—that likes to hang out near a zoo in the Austrian Alps. Every day these ravens conspire to steal the food that's set out for the wild boars there.
"So we have a really great opportunity to really watch those individuals daily."
University of Vienna cognitive biologist Markus Boeckle. He spends lots of time ignoring the zoo animals and watching the ravens.
"And what we found is that every time they come they do those food calls, which is very typical for the ravens when they are close to potentially dangerous food resources."
(Raven haa call sounds)
The ravens use these calls to recruit their buddies to show up, both to reduce potential dangers from predators and to overpower dominant ravens who might be trying to hoard all the food for themselves.
But Boeckle and his colleagues began to suspect the calls revealed other information.
"So we had the feeling we could say, this is a juvenile, this is a sub-adult, and this is most probably an adult, just by listening to the calls."
If the researchers could use the calls to distinguish among ravens, then perhaps the ravens themselves could do so too. So Boeckle and his team recorded the calls of around a hundred known individuals—all of which had previously been catalogued by weight, age and sex and were identifiable by colored leg bands.
The researchers combined that data with the acoustic properties of their calls and dumped everything into a computer program. And as they suspected, there were differences in the frequency, duration, and amplitude of the calls that could sort the ravens according to sex and age. The results were published in the journal Frontiers in Zoology.
"So the benefit is, especially for birds like ravens who travel long distances every day, that whenever you encounter a new individual, or listen to a new individual, you are already able to categorize one of the birds just based on the calls... So this really helps to assess whether you're going to be in an aggressive situation or whether you're going to be the more dominant individual, just by listening to the call."
To be clear, the researchers showed that they could categorize ravens according to their calls, not that ravens actually do so. That's what Boeckle and his team are working on now.
Still, the study shows that while a call can primarily refer to some external object, like food, it can also transmit additional social information. And since these sorts of calls are thought of as the precursors for language, this study might shed light on how a simple system for communication can evolve into something far more complex—such as me talking to you right now.
Thanks for the minute for Scientific American — 60-Second Science. I'm Jason G. Goldman.
渡鸦有一个众所周知的秘密，那就是它们喜欢在奥地利阿尔卑斯山的动物园附近游荡，渡鸦群在英语中有“密谋”的含义 。这些渡鸦每天都会合谋窃取动物园为野猪准备的食物 。
维也纳大学的认知生物学家马库斯·博科说到 。他没有关注动物园里的其他动物，而是花了大量时间来观察渡鸦 。
如果研究人员能用叫声来分辨渡鸦，那也许渡鸦自己也可以 。因此，博科和团队记录了约100只已知渡鸦的叫声，此前这些渡鸦均按体重、年龄和性别分类，并用不同颜色的腿带来区分 。
研究人员将这些数据和它们叫声的声学特征结合起来，并将所有信息输入计算机程序中 。正如研究人员所猜测的那样，根据性别和年龄的不同，渡鸦叫声的频率、持续时间和振幅有所不同，可以以此来进行区分 。这项研究结果发表在《动物学前沿》期刊上 。
“特别是对渡鸦这种每天都要长距离飞行的鸟类来说，好处是无论何时遇到新个体，或是听到新个体的叫声，都能仅靠叫声来进行分类 。所以，仅凭听叫声就能帮助评估是否要进入进攻状态，或是否要成为更有主导力的个体 。”
要明确的是，研究人员发现，他们可以根据渡鸦的叫声对其进行分类，但并不是说渡鸦真的分类了 。这是博科和团队正在开展的工作 。
尽管如此，研究表明，虽然叫声的内容可能主要涉及食物等外部对象，但也可以传送额外的社交信息 。而且，由于这种叫声被认为是语言的前身，因此这项研究可能会阐明一个简单的交流系统如何演变成更加复杂的事物，比如我现在正在和你说话这样 。
谢谢大家收听科学美国人——60秒科学 。我是杰森·古德曼 。
1. hang out 闲逛，逗留；
Some of my fondest memories are when I've put together a large group of friends and did nothing but hang out.
2. show up 如约赶到；出现；露面；
When you agree to sh ow up at a certain time, be there.
3. according to 依据，根据，依照；
The salary will be fixed according to qualifications and experience.
4. shed light on 使（某事）显得非常清楚；使人了解（某事）；
Uponthe new experiment may shed light on how animals respond to dangers.