Atelopus is a large genus of true toads, commonly known as harlequin toads or stubfoot toads, from Central and South America, ranging as far north as Costa Rica and as far south as Bolivia. Atelopus species are small, generally brightly colored, and diurnal. Most species are associated with mid-to-high elevation streams. This genus has been greatly affected by amphibian declines, and many species are now considered endangered, while others already are extinct. Almost 40% of the described species in the genus are considered possibly extinct; this is raised to 45% when data deficient species are added; this number may be even higher, given that the genus contains many undescribed species that could also be extinct, and many of the species considered critically endangered but extant may have gone extinct after the last surveys that detected them, or could go extinct in the future. While threatened by habitat loss, pollution, and introduced species, the primary cause of these declines appears to be the chytrid fungus Batrachochytrium dendrobatidis. For example, there are 32 known Atelopus species in Ecuador. One of these is data deficient, two are endangered and the remaining are critically endangered. Almost half the Ecuador species have not been recorded in a decade or more and are likely extinct. In some species conservationists have established captive colonies as a safeguard. However, numerous Atelopus species have been rediscovered decades after their last sighting, such as A. arsyescue, A. mindoensis, A. bomolochos, A. ignescens, A. balios, A. longirostris, A. subornatus and A. varius.
