Abstract
This paper reports long-term data on the seasonality of sightings of Ucayali bald uakaris, Cacajao ucayalii at the Estación Biológica Quebrada Blanco (EBQB). Sightings were most common during the drier parts of the year and rarer during the rainy season. This suggests that the C. ucayalii groups travel long distances and seasonally move (migrate) between different parts of presumably large home ranges and between different habitats (terra firme forest, Amazon floodplain forest). Areas to protect this Neotropical primate must be large enough to allow for sufficient seasonal access to these vegetation types.