To study the geographic distribution and demographic characteristics of Pithecia aequatorialis in Peruvian Amazonia, we undertook surveys and transect census in three river basins (R?o Itaya, R?o Tigre and R?o Curaray) between 2004 and 2008. A total of 123 groups of P. aequatorialis was encountered during 1623 km of transect walks. Group size was uniform among the three areas (3.4-3.6 individuals), but surprisingly, population densities were higher in the area with strong hunting pressure (R?o Itaya: 7.8 ind./km(2), vs. 5.6 and 5.9 km(2) in the R?o Tigre and R?o Curaray basins, respectively). The most common group composition included an adult pair with one offspring. Groups with more than one adult male and/or female accounted for 35% of sightings. Our observations extend P. aequatorialis range in Peru further south to the area between the R?o Tigre and R?o Corrientes, but exclude the area to the north between the R?o Curaray and R?o Napo. These findings are in contrast to previous distribution maps. P. aequatorialis was rarely seen in interspecific association during our censuses.
Animals Behavior, Animal