为什么黑猩猩喜欢向树扔石头?

为什么黑猩猩喜欢向树扔石头?

Researchers recently discovered some unusual behavior in chimps living in the forests of West Africa. An adult male in the wild would pick up a rock, throw it at a tree while yelling, and then run away.

研究人员最近在生活在西非森林中的黑猩猩身上发现了一些不寻常的行为。野外的成年雄性会捡起一块石头，一边大喊大叫一边扔向一棵树，然后逃跑。

Photo: Abeselom Zerit/Shutterstock

Although researchers aren't certain why the chimps fling the rocks, they have a hint: The chimps seem to prefer trees that create longer-lasting, more resonant sounds when struck.

虽然研究人员还不确定为什么黑猩猩会扔石头，但他们有一个提示:黑猩猩似乎更喜欢在受到撞击时发出更持久、更共振的声音的树。

A team of researchers from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, first uncovered this behavior three years ago. Because the actions appeared to be localized, the researchers suggested the purpose was a local tradition and was likely part of some sort of ritual, Phys.org reports. But they weren't sure what purpose the ritual served.

德国莱比锡马克斯·普朗克进化人类学研究所的一组研究人员三年前首次发现了这种行为。因为这些行为似乎是局部的，研究人员认为这是当地的一种传统，可能是某种仪式的一部分，Phys.org报道。但他们不确定这种仪式的目的是什么。

So the group devised more experiments to determine why the chimps were so interested in lobbing rocks at trees. This time around, they went to the same areas but set up microphones to capture the sounds of the stones as they were thrown. While waiting for the chimps to hurl the rocks, the researchers threw the stones at 13 different kinds of trees in various situations.

因此，研究小组设计了更多的实验来确定为什么黑猩猩对用石头砸树如此感兴趣。这一次，他们去了同样的地方，但设置了麦克风来捕捉扔石头的声音。在等待黑猩猩投掷石块时，研究人员在不同的情况下向13种不同的树木投掷石块。

"It was quite fun, I have to say," coauthor and primatologist Ammie Kalan tells Science.

“我不得不说，这很有趣，”合著者兼灵长类动物学家阿莫米卡兰告诉《科学》杂志。

Researchers analyzed all the recordings and found that the chimps tended to prefer throwing rocks at trees that made lower, longer-lasting sounds. Often these were trees that had exposed roots.

研究人员分析了所有的录音，发现黑猩猩更喜欢向发出低而持久声音的树扔石头。这些树的根常常暴露在外。

In their findings, published in Biology Letters, the researchers write that "low-frequency sounds travel further in the environment and are better suited for long-distance communication." In addition, more resonant sounds will last longer in the environment.

在他们发表在《生物学快报》上的研究结果中，研究人员写道:“低频声音在环境中传播得更远，更适合远距离交流。”此外，更有共鸣的声音在环境中会持续更长的时间。

But if chimps were looking to communicate, it would be more effective for them to drum on the trees or choose the ones that made the loudest noises when struck.

但是，如果黑猩猩想要交流，对它们来说，在树上敲鼓或者选择那些在被击打时发出最大声音的声音会更有效。

Because the researchers saw chimps stick to the same trees and never choose new ones, location could be a factor. Kalan tells Science that maybe the locations of the trees have something to do with nearby resources like food and water, and the sound is a signal to others where to find them.

因为研究人员发现黑猩猩们总是呆在同一棵树上，从不选择新的树，所以位置可能是一个因素。卡兰告诉《科学》杂志说，也许这些树的位置与附近的资源有关，比如食物和水，而这些声音是给其他人找到它们的信号。