Habitat use by Chiropotes satanas utahicki and syntopic platyrrhines in eastern Amazonia.

Primates were surveyed at two sites in the Xingu-Tocantins interfluvium, in eastern Amazonia, where at least eight platyrrhines are known to occur, including the endemic Chiropotes satanas utahicki, vulnerable to extinction. Only three other forms; Alouatta belzebul belzebul, Cebus apella apella, and Saguinus midas niger; were recorded at both sites. Data on habitat use (forest type and strata) were collected in standard line transect surveys and analyzed with relation to the availability of forest types, as well as between sites and species. The smallest- (S. midas) and largest-bodied (A. belzebul) species were relatively common at the continuous forest site, where they exhibited a significant preference for primary terra firme forest. At this site, Cebus demonstrated a significant preference for liana and flooded forest in contrast with primary or secondary terra firme forests. The medium-sized Cebus and Chiropotes were more common in the isolated forest fragment (where they were also observed together frequently), but no clear habitat preferences were found at this site for any species. A. belzebul occupied significantly higher forest strata than other species, which all used relatively similar levels. C.s. utahicki was active in much lower forest strata than other bearded sakis, whereas S. midas was observed at much higher levels than at other sites in eastern Amazonia. It remains unclear whether and to what extent observed patterns are determined by differences between taxa, populations, or ecosystems, but the data indicate that C.s. utahicki is relatively tolerant of habitat disturbance.