The diet of wild black-fronted titi monkeys Callicebus nigrifrons during a bamboo masting year

Black-fronted titi monkeys, Callicebus nigrifrons, are endemic primates of the Atlantic forest of Brazil, and little is known about their diet and how it is affected by seasonal changes. The aim of this study is to analyze the diet of C. nigrifrons during a bamboo masting year. This study was conducted in the reserve RPPN Santuário do Caraça, MG, and the collection of data was carried out from January 2007 to January 2008 through monthly campaigns. The feeding behaviour of four habituated groups in the same forest fragment was observed. The data were collected through focal animal observations of 10 min each with instantaneous recording of behaviour every 30 s, totalling 220.5 h of observations during 71 field days. The diet of groups consisted of 43.4% fruit, 37.0% seeds, 8.2% leaves, 6.2% flowers, 2.5% animal matter and 2.7% non-identified/other items. At least 51 species of plants were consumed. More than half of the diet comprised only five species: Merostachys fischeriana (bamboo, 32.3%), Solanum cinnamomum (nightshade, 8.7%), Vitex spp. (Lamiaceae, 4.5%), Casearia decandra (wild honeytree, 3.8%) and Amaioua guianensis (woody dioecious species, 3.7%). According to the values obtained from Levins' index analysis (0.05-0.28) our subjects had a narrow diet width. The individuals in this study were able to incorporate significant amounts of bamboo seeds in their diet, and this was inversely related to fruit consumption. In conclusion, C. nigrifrons was able to amply exploit a bamboo masting event, which generated a narrow diet width.