During the evolution bait flys to avoid competitions with other animals which live in ocean or on land . successful evolution of echolocation system in the sky makes them avoid competitions with birds . so thy occupied a special ecological niche - sky of night 在进化的过程中，蝙蝠避开与其他海陆兽类的竞争而飞向天空；在空中，回声定位系统的高度进化使它们避开与鸟类的竞争而占据了独特的生态位- - - -黑暗的夜空。
