This is one of the reasons why some males birds have exotic plumes, why elk carry hefty antlers (a sign of a healthy immune system), and why male fiddler crabs have such large claws.

这正是大自然为什么让一些雄鸟长着充满异国情调的羽毛或让麋鹿拥有大而笨重的鹿角(这也是一个生态系统健康的标志)的原因之一。