They're considered amphibians, and amphibians are reproductively tied to the water.
它们被认为是两栖动物,而两栖动物与水有生殖联系。
《分钟地球》趣味科普(精选双语)
So unless we honest-to-goodness get rid of every reproductively active individual, eventually, they'll return as vigorously as before, keeping us constantly on our toes.
A Dutchman named Comeille de Pauw announced in a popular work called Recherches Philosophiques sur les Americains that native American males were not only reproductively unimposing, but so lacking in virility that they had milk in their breasts.