Seasonality and socioecology: The importance of variation in fruit abundance to bonobo sociality

The assumption that nonseasonal, evergreen, rain forests contain more conti nuously available food resources than seasonal rain forests is fundamental to comparisons mane between the socioecology of the male-bonded Pan troglod ytes and the female-based social system of the Pan paniscus. Chimpanzee fem ales may be less social due to the high costs of feeding competition, where as in the more food-rich central African rain forests such as the Lomako fo rest, female bonobos can associate and socially bond. The Lomako Forest exp eriences two wet and two dry seasons a year. Data on fruit abundance and so ciality show that despite monthly variation in fruit availability, there wa s no consistent seasonal variation in fruit abundance or dietary breadth. B onobo use of nonfig fruits, figs, THV and leaves did not follow seasonal pa tterns. Leaves and THV may act as complementary sources of plant protein an d their use was inversely correlated Monthly variation in fruit abundance w as associated with a significant decrease in the number of males in a party but not in the number of females. Focal males were frequently solitary dur ing 1 of the 3 months with the smallest party sizes. lit contrast, females remained social with each other throughout the year. Therefore, seaonality at Lomako appeared to be less marked than at comparable chimpanzee sites, s uch that the variation in fruit abundance did not fall below a level that p rohibits female sociality.