The scientific and conservation communities recognize toads of genus Atelopus as among the most vulnerable of all amphibian groups, with over 75% of the species assessed as “Critically Endangered” by the International Union for the Conservation of Nature (IUCN) Red List. Atelopus varius, known as the Harlequin Toad, has been thought to be extinct in Costa Rica since the mid-1990s. There have been four rediscovered populations of the species since 2004. This report presents the fifth reappearance of A. varius, this time in the Alexander Skutch Biological Corridor (ASBC) in the Pacific Slope foothills of La Amistad International Park, Costa Rica, which represents a new location. Previously, the pattern of reappearance of this species has been unclear. In this study, the discovery of a new population of A. varius allows us to evaluate the presence of Bd infection and offer critical natural history remarks. In total, 25 different individuals were identified. All samples analyzed for Bd diagnosis were negative. In contrast to other A. varius populations, this one was mostly found high above the riverbed, often in the foliage, tree trunks, and bromeliads, from 1–6 m above the water both during day and night. The absence of Bd infection in these Harlequin Toads, a highly susceptible species, in an area identified as having a high probability of Bd occurrence, suggests that this behavior could have helped this population survive by reducing infection risk. Moreover, the distribution of A. varius may have changed in the last 50 years, by penetrating higher in the montane regions of the Talamanca mountains, a change in distribution that might also help its survival of some environmental stressors. With the discovery of a new locality for A. varius, this study offers an animal behavior argument to account for species recovery in general, as well as a possible expansion of what has been accepted as the historical distribution of this species.
