This is a species of poison-dart frog from Tambopata, Allobates femoralis.
While not very large or particularly showy–or very poisonous, for that matter–these frogs are very interesting in that they show extreme variation throughout their range. Researchers have discovered that distinct populations that are separated by geologic barriers, such as large Amazonian rivers, have different calling patterns; some populations have a two-note call, whereas other populations have a three- or four-note call. These might seem like unimportant differences, but they may be all that are required to isolate populations and lead to speciation. For instance, if females in one region prefer males that have a four-note call, they might not breed with males that have, say, a two-note call, and over time this can cause a new species to arise from that population. Add in large rivers that form barriers to populations mixing, and you’ve got the potential for a huge amount of genetic diversity and confusion for biologists trying to understand the distribution of frog diversity here. Just another way in which the Amazon continues to reveal its biodiversity to those who pay close attention to it!