会拉出方块的动物

有一种动物，它的粪便是方块形的。把这个故事分享给那个觉得大自然没有幽默感的人。在澳大利亚，有一种身形低矮、体重不轻、浑身长毛的动物，叫袋熊。它整夜挖掘长长的地道、吃草，留下的却是一个个整整齐齐的小方块。

One animal makes square poop. Send this to someone who thinks nature has no sense of humour. In Australia there is a low, heavy, furry animal called a wombat. It digs long tunnels, it eats grass all night, and it leaves behind small neat cubes.

多年来没有人能解释这个现象。要做出棱角原本是很困难的事情，地球上其他任何动物排出的软便，不是圆的就是条状的。于是科学家仔细研究了袋熊的身体内部，在它肠道的最后一段找到了答案。

For years nobody could explain it. Corners are difficult to make. In every other animal on the planet, soft things that leave a body come out round or long. So scientists looked closely inside a wombat and found the answer in the last stretch of its gut.

这段肠道的四周并不是均匀一致的。有些部分的肠壁较硬，收缩得又快又用力，有些部分则较软，只是单纯地伸展。较硬的部分一次又一次地把棱角挤压出来，直到形状固定成型。之后，袋熊会把做好的方块堆放在岩石和木头上，告诉其他袋熊这片地盘是谁的。圆形的粪便会直接滚走，而方块却能稳稳地留在原地。

That stretch is not the same all the way around. Some parts of the wall are stiff and squeeze hard and fast. Other parts are soft and simply stretch. The stiff parts press the corners in, again and again, until the shape sets and holds. The wombat then stacks the finished cubes on rocks and logs to tell other wombats whose ground this is. Round ones would roll straight off. Cubes stay exactly where they are put.