translation.en: They could outsource all their problems: protection from predators, food-finding ...  The only cost in most flocks -- not even this -- a loss of free mating.
translation.zh: 他们把所有问题都转交给了牧羊人 比如免受捕食者的威胁，觅食以及保持健康等等 唯一的成本是不能自由交配