SIGNIFICANCE OF SILICA IN LEAVES TO LONG-TAILED MACAQUES (MACACA-FASCICULARIS)

Leaves of two plant species eaten by Macaca fascicularis in Bukit Tima h Nature Reserve, Singapore, were collected and colour-tested. Leaves matching those eaten by M.fascicularis were examined by energy-dispers ive X-ray micro-analysis. The leaves of Streblus elongatus (Moraceae) and Gluta wallichii (Anacardiaceae), together forming 19.6% of the lea f diet of the macaques, contained silica. In G. wallichii, this is in the base of hairs that project from the underside of the leaf, whereas S. elongatus leaves have short sharp siliceous trichomes which are de nsely packed on the undersurface of leaf veins. We predict from an ind entation analysis that chewing on the latter species could cause denta l microwear at low occlusal forces. The leaves are reportedly common i n the diet of three other primate species in peninsular Malaysia and t he finding could have general significance for studies of dental wear.