Because A female is a mosaic because she consists of a mixture of two kinds of cells: each with different functional chromosomes. Because XY males have a single X chromosome, while XX females have two of them, some kind of adjustment is needed: the X chromosome inactivation.
The number of Golden Toads people saw declined from 1,500 to zero in such a short period of time. Scientists suspect that conditions related to climate change was the reason for their extinction