Whales Use Song as Sonar鲸鱼以歌声为声呐

伯特·甘比尼

Any quick Internet search for recordings of humpback whale song returns audio compilations that can receive tens of thousands， if not millions， of visits.

With such quantifiable popularity， you might ask， “Who doesn’t love listening to whale song？” One surprising answer might be， “whales，” according to an intriguing model developed by a University at Buffalo researcher.

It’s not that listening whales ignore the singers of their species. The question for Eduardo Mercado III， a professor in UB’s Department of Psychology， is how humpback whales perceive the song， which is among the most sophisticated acoustic performances in the animal kingdom.

Mercado has published a paper in the journal Frontiers in Psychology that hypothesizes whale song helps singers perform a type of auditory scene analysis.

He’s not the first researcher to suggest the idea of humpbacks using sonar， but he’s probably the first to analyze the possibility that songs might be used for sonar.

Mercado’s model proposes that the sender is also the receiver. He says whale song provides useful information to the singing whale， not just listening whales.

“Nearly every biologist is going to say this is nonsense， but I still maintain the direction of the current scientific consensus is wrong，” says Mercado. “Assuming whales hear the songs as beautiful displays like a human might is imposing our perception on theirs.”

“What are the whales perceiving？” he asks. “Scientifically， we have to consider that.”

The current assumption has remained for decades that whales sing predominantly for reproductive purposes， using their song as sexual signals that provide a way for females to find high-quality males; for males to attract females; or for males to compete with other males.

That’s the scene for the biologist. In each case， the listening whale would be doing most of the song analysis.

But Mercado says the evidence collected so far provides little support for the sexual advertisement hypothesis.

In his view， the data points more toward it being the singer， not the listener， who is doing most of the analysis through echolocation.

Mercado says humpbacks sing as a way to explore their world.

The goal is still predominantly reproductive， but the song in this case is a like a searchlight that informs singers about the presence of other whales， the direction those whales might be heading and whether or not the singer might be able to catch up to them.

“That’s why they’re singing，” he says. “They’re trying to create a scene that would not be there otherwise. When they create these echoes it’s like shining a searchlight in the dark.”

Mercado began to develop his model by examining the physics of the problem.

To create a simplified version of what would need to happen for echolocation to work he started asking questions： How could this work？ What echoes might come back to singers？ How strong would they be？ Could they be resolved from other sounds？ And what information could they provide？

“The model suggests that singers could easily obtain information about the location of other whales，” he says.

As a graduate student， Mercado accepted a job analyzing whale song. But much of what he heard didn’t make sense. For instance， the library of sound used by whales was changing in different years， demanding whales process new songs every year.

“That’s more difficult than humans trying to annually learn a new language，” says Mercado. “For whales， it isn’t just language， but a whole new range of sounds and new patterns of sounds.”

“For us， it would be like trying to communicate with a new species of humans with different vocal chords that produce a radically different language.”

This apparent learning ability is what interested Mercado， an expert on the effects of learning on brain function， in humpback whale song.

“If my hypothesis is valid it means that whales are doing something much more complicated than what humans can even begin to approach，” he says. “If we understood how whales accomplish this， it could help us understand better how brains work in general.”

Mercado understands why researchers would be skeptical about his model， but he says it’s a testable hypothesis.

If he’s right， Mercado says it should change the direction of how we study whales.

“It’s easy to get locked into believing something that seems obvious. But looks， or in this case， sounds， can be deceiving，” he says. “Right now， whale song is being analyzed in a way that might not be accurate.”

在互聯网上快速搜索座头鲸的歌声录音，每次都能搜到不少的音频选辑，访问量没有数百万也有数万。

这种可量化的人气也许会让你好奇发问：“谁不爱听鲸鱼的歌？”纽约州立大学布法罗分校的一名研究员开发出一个有趣的模型，该模型给出了一个令人意想不到的答案——鲸鱼。

这并不是说听歌的鲸鱼对其种群中的歌唱者不予理睬。布法罗分校心理学系教授爱德华多·默卡多三世所关注的问题是，座头鲸如何感知歌声。鲸鱼歌唱可是动物界最复杂的声学表演之一。

默卡多在《心理学前沿》杂志上发表了一篇论文，他在文中提出一种假说——唱歌的鲸鱼可以借助歌声来完成一种听觉场景分析。

默卡多不是第一个提出座头鲸使用声呐的研究者，但他很可能是第一个分析座头鲸能将其歌声用作声呐的人。

默卡多的模型提出，发声者同时也是听声者。他认为，鲸鱼的歌声不仅将有用的信息提供给听歌的鲸鱼，也提供给唱歌的鲸鱼自己。

“几乎每一位生物学家都会认为我在胡说八道，但我坚信目前科学界的共识在方向上出了错。”默卡多表示，“他們认为鲸鱼就像人类一样，大概是在欣赏歌声之美，这是把人类的感知强加给它们。”

“鲸鱼在感知些什么呢？”他问道，“科学上，我们必须思考这个问题。”

几十年来，人们一直认为鲸鱼歌唱主要是为了繁殖目的，它们用歌声传递求偶信号，雌鲸借以寻找优质雄鲸，雄鲸则以此吸引雌鲸或与其他雄鲸竞争。

这就是生物学家眼中的场景。在每种情况下，都是听歌的鲸鱼做大部分的歌声分析工作。

但默卡多指出，目前为止收集到的证据几乎无法支撑上述的求偶宣传假说。

在他看来，资料更能证明的是，通过回声定位进行大多数分析工作的是歌唱者，而非听歌者。

默卡多表示，座头鲸以歌唱作为探索世界的一种方式。

它们唱歌的目的主要还是为了繁殖，但这种情况下，歌声就像一盏探照灯，告知歌唱者其他鲸鱼的存在、它们可能的前进方向，以及自己能否赶上它们。

“这就是它们唱歌的原因。”他说，“它们正在试图创造一个只有唱歌才会出现的场景。它们创造回声就像在黑暗中点亮一盏探照灯。”

默卡多开始通过探查问题的原理来建立模型。

为了简化回声定位起作用的相关条件，他开始追问：这是如何起作用的？哪些回声会反馈给歌唱者？这些回声有多强？能否将回声与其他声音区别开？它们能提供什么样的信息？

他说：“模型显示，唱歌的鲸鱼能轻易获知其他鲸鱼的位置信息。”

读研究生时，默卡多接受了一份分析鲸鱼歌声的工作。不过，他听到的大多数歌声都毫无意义。比如，不同的年份，鲸鱼使用的声音数据一直在变，要求它们每年要加工新歌。

“这比人类每年都尝试学习一门新语言更难。”默卡多说，“对鲸鱼来说，要加工处理的不单是语言，而是一套全新的声音和新的声音模式。”

“对我们来说，这就像是试图与一个新人种进行交流，这个新人种的声带与我们有别，说出的语言也与我们截然不同。”

默卡多的专长是研究学习对大脑功能产生的影响，正是座头鲸歌声中体现出的这种显见的学习能力引起了他的兴趣。

“如果我的假设成立，这意味着鲸鱼所做的事情远比人类所能企及的复杂得多。”他说，“如果我们明白了鲸鱼是如何做到的，这将帮助我们更好地理解大脑普遍的工作机理。”

默卡多明白为什么研究人员会对他的模型持怀疑态度，但他说这是一个可验证的假设。

默卡多说，如果他是对的，这应该会改变我们研究鲸鱼的方向。

“人们很容易坚信一些看似显而易见的事情。但外表，或我们这里说的声音，可能有欺骗性。”他说，“当下，人们研究鲸鱼歌声的方式或许并不准确。”

（译者单位：江西师范大学）