32 A Natural Contract

It's practically a business arrangement. A symbiosis is a partnership between two living organisms, and it benefits both of the organisms. Nature provides us with many extraordinary examples of symbiosis in the animal kingdom.

It's not an unusual sight in Africa to see a tiny bird, the egret, standing confidently on the massive back of a rhinoceros. This powerful, and sometimes fierce, animal doesn't at all mind giving the little bird a free ride. In return, they get a free meal. The relationship between the harmful ticks and less fortunate creatures constitutes a symbiotic partnership.

Another bird called the rhino and the egret is a happy walking up and down the length of a crocodile's back. The crocodile doesn't object because the plover is the alligator's dentist. The plover cleans the crocodile's mouth and clear the valuable teeth. The pickings provide the plover with a meal. The bird's job does not appear to put it in any danger, for the crocodiles never seem to harm the little feathered creatures.

Some symbiotic partners cooperate by sharing a home. For instance, a small blind fish called a goby will often cohabit with a shrimp. The goby keeps the shrimp's unusual burrow clean, and in turn the shrimp procures food for the goby. In all of these examples, each partner benefits from the curious but necessary relationship.

32 自然契约

这实际上是一种“商业合作”。共生是两种生物之间的伙伴关系，对双方都有益。自然界在动物王国里给我们提供了许多非凡的共生例子。

在非洲，看到小白鹭自信地站在犀牛巨大的背上并不罕见。这种强大且有时凶猛的动物完全不介意让小鸟免费搭便车，作为回报，它们能获得免费的食物。牛椋鸟与犀牛之间的关系就是一种共生伙伴关系。

另一种叫“燕鸻”的鸟会在鳄鱼背上快乐地走来走去。鳄鱼并不反对，因为燕鸻是鳄鱼的“牙医”：它会清理鳄鱼的嘴巴，清洁其珍贵的牙齿，而这些食物残渣就能让燕鸻饱餐一顿。这种工作似乎不会让燕鸻陷入危险，因为鳄鱼似乎从不会伤害这些小小的羽毛生物。

有些共生伙伴通过共享栖息地来合作。例如，一种叫“虾虎鱼”的盲眼小鱼常和虾同居：虾虎鱼会保持虾那奇特洞穴的清洁，作为回报，虾会为虾虎鱼获取食物。在所有这些例子中，每个伙伴都能从这种奇特却必要的关系中获益。