PHYSICAL AND CHEMICAL-PROPERTIES OF FRUIT AND SEEDS EATEN BY PITHECIA AND CHIROPOTES IN SURINAM AND VENEZUELA

Pithecia pithecia and Chiropotes satanas are seed predators that eat fruits with hard pericarps. We measured resistance to puncturing and crushing of fruit and seeds eaten by these two pitheciins at two localities. in evergreen rain forest at Raleighvallen-Voltzberg Surinam, and in tropical dry/transitional moist forest on islands in Gun Lake, Venezuela. Average measurements of pencarp hardness were similar at both sites for fruit eaten by Chiropotes but a higher maximum value was obtained ut the rainforest site. Chiropotes and Pithecia both ate fruits that had harder pericarps than did fruits eaten by Ateles paniscus but crushing resistances of seeds eaten were lower than values for Ateles, Thus, both pitheciins selected fruits with hard pericarps and soft seeds, although there were notable intergeneric differences in hardness of fruit ingested. When fruit became scarce, Pithecia ate more flowers, while Chiropotes continued to eat fruits with hard seed coverings. Chemical analysis of species of seeds eaten by Pithecia suggests that they avoided seeds with extremely high tannin levels, though they tolerated moderate tannin levels in combination with high levels of lipids. We propose that sclerocarpic harvesting (the preparation and ingestion of fruit with a hard pericarp) allows pitheciin monkeys to obtain nutritious seeds, with reduced tannins, that are softer than those ingested by other frugivores.