ADRIAN A. BARNETT
School of Human & Life Sciences, Roehampton University, London SW15 5PU, UNITED KINGDOM.
The feeding ecology, general behaviour, size of groups and use of habitat of the goldenbacked uacari, Cacajao melanocephalus ouakary, was monitored for 14 of a 19-month period in Jaú National Park, Amazonian Brazil between October 2006 and April 2008. The botanical composition and phenology of the habitats was also studied.
The diet is dominated by seeds of immature hard-husked fruits. Leaves, flowers and pith served as fall-back foods. The diet items eaten were the most abundant at the moment, with items previously ignored incorporated when the abundance of other foods dropped relative to them. Most feeding occurred in the forests upper strata, but with occasional visits to the ground and low bushes when little food was available elsewhere. Feeding bouts were short, with uacaris generally spending less than three minutes in a feeding patch before moving to the next. Individual adults generally foraged one-per-patch, though up to five animals might forage simultaneously in canopies of very large trees. Uacaris were recorded feeding on 136 plant species. Micropholis venulosa, Echweilera tenuifolia, Buchenavia ochrograma, Pouteria elegans and Mabea nitida were the most abundant species in the diet, and were eaten for both leaves and seeds. Flowers of E. tenuifolia were also eaten. The most important diet families were Sapotaceae, Fabaceae and Lecythidaceae. Invertebrates represented less than 2% of the diet, and were mostly ants, termites and caterpillars. Many were free-ranging, but shoot-boring larvae were also extracted and eaten. Additionally, fruits of five species were recorded being eaten with insect larvae still living inside them.
Uacaris use two habitats, terra firme (a never-flooded mosaic of several forest sub-types) and igapó (a seasonally-flooded forest that occurs between terra firme and the open river). Igapó’s fruiting season match the flood pulse and so are strongly condensed. Those of terra firme are less so. In 14 month, uacaris were seen exclusively in terra firme during 3 months, only in igapó during 9 months and in both during 2 months. Movement between the habitats appears to follow fruit availability. When there is little fruit in either, uacaris remain in the igapó and feed (mostly) on new leaves.
The activity budget was dominated by moving, paused feeding and feeding-whilemoving. Very little resting was observed and almost no physical social interactions such as aggression or grooming. Adult C. m. ouakary were rarely seen closer than 6m apart, and groups were often diffuse, spreading over several hundred meters. Reproduction appears to occur twice a year, very young animals being seen in December and May. Observed group size varied between 2 and 51. Groups of 6-15 were most commonly seen. Group size varied with the season and habitat, being largest (30-51) in neverflooded rainforest and smallest (4-6) in the igapó when little fruit was available and fallback foods dominated the diet.
At least 10 of the species in the C. m. ouakary diet are used as timber in Amazonia. While this is not a cause of conflict in Jaú National Park, it might be so elsewhere in the animal’s range. This has been the first long-term study of the ecology of golden-backed uacaris in Brazil and suggestions are made for future research.