On the geographic distribution of the bald uakaris (Cacajao calvus ssp.) in Brazilian Amazonia

An understanding of a species’ geographic distribution is essential to assess, plan, and develop strategies for its conservation. The geographic distribution of the bald uakari, Cacajao calvus, and its component subspecies has been poorly investigated, with disjunct distributions being reported in Brazil and Peru. In this study, we reveal new records of bald uakari occurrence based on multi-year surveys, a literature review, and an examination of vouchers available in six zoological collections, clarifying the geographic distribution of all subspecies. We confirm that C. c. calvus has a disjunct distribution with populations along the rios Tarauaca and Pauini, 250 km away from those on the left bank of middle Rio Jurua and lower Rio Jutai; and 650 km from the population of the Mamiraua Sustainable Development Reserve (Mamiraua SDR). Cacajao c. rubicundus has a disjunct distribution with three isolated populations 1) inhabiting the flooded forests of the Rio Solimoes and the Parana (channel) Jacurapa, 2) the left bank of the lower Rio Jutai; and 3) in the Auati-Parana. Cacajao c. novaesi has the smallest geographic distribution of the bald uakaris, occurring only in the Gregorio-Tarauaca interfluvium. Cacajao c. novaesi and C. c. calvus are separated by the Rio Tarauaca, which is also a significant geographic barrier for other primates, including titi and saki monkeys. We also confirm the occurrence of Cacajao c. ucayalii in Brazil in the Serra do Divisor National Park. This Peruvian subspecies has the most extensive range, with isolated populations found in areas completely separated from the lowlands. The patchy distribution of Cacajao calvus provides a unique opportunity to understand how local environmental variation may have promoted ecological flexibility for the successful establishment of isolated populations.