Amphibians have a skin that is different from that of many other organisms, as they use it for important functions such as breathing and drinking water. Because of this, amphibians need specific humidity conditions and are very sensitive to environmental changes. Their sensitivity has positioned them as bio-indicator organisms, meaning that the presence of amphibians provides scientists with information on how the ecosystem in which they are found is functioning. In the upper basin of the Pance River, five species of frogs have been found so far, all belonging to the family of the strabomantids. This group is characterized by "skipping" the tadpole stage in their development, as a very small frog hatches directly from their eggs. This is a common strategy for frogs in mountain ecosystems, as they do not have to rely on lentic water bodies, but can hatch from moist soil such as leaf litter in the forest interior. Among the frogs in the Bachué Nature Reserve, endangered and endemic species have been found, such as the Ruiz's robber frog (Strabomantis ruizi) or the San Antonio robber frog (Pristimantis calcaratus).