Many animals living in the gypsum dunes at White Sands National Monument match the white sands on which they live. Animals reported to be lighter-colored in the dunes than in non-dune populations include insects, spiders, scorpions, lizards, mammals, and even toads (see Table 1). These white animals raise several questions. Why, for example, did white animals evolve in the dune field? Why are some dune-field animals white and others not? How do the animals become white? Much research is still necessary to fully answer these questions, but our current understanding of these issues is summarized below.