MINERAL AND PHYTOCHEMICAL INFLUENCES ON FOLIAGE SELECTION BY THE PROBOSCIS MONKEY (NASALIS-LARVATUS)

Primate diets may be influenced by the phytochemical composition of po tential food resources. This study examined the protein, fiber, and mi neral content of leaves from plant species used as food resources by t he proboscis monkey (Nasalis larvatus) in Tanjung Puting National Park , Kalimantan Tengah, Indonesia. In addition, leaf samples were collect ed from nonfood resources based upon relative density in previously es tablished vegetation plots. Higher concentrations of crude protein, ph osphorus, potassium, and zinc were found in young leaves. Mature leave s had higher levels of magnesium, manganese and calcium compared to yo ung leaves. Leaves from species used as food resources were significan tly higher in protein (9.9% vs. 8.5%) and lower in fiber (30.5% vs. 40 .0% acid detergent fiber) than the leaves from species not used as foo d sources. Food resources also contained higher concentrations of phos phorus and potassium; nonfood resources contained higher concentration s of calcium and manganese. Proboscis monkeys appear to follow the typ ical colobine trend: a diet relatively high in protein and low in dige stion inhibitors (fiber). Little previous work has examined mineral co ntent as a selection factor in primate food choices. Leaves from speci es used as food resources contained less calcium (0.35%), iron (34 mg/ kg) and phosphorus (0.15%) than dietary standards established for capt ive nonhuman primates, but values were similar to those established fo r ruminant herbivores. Other mineral concentrations (potassium, magnes ium, manganese, sodium, and zinc) met or exceeded recommended levels f or both primates and ruminants. Comparison of diverse nutrients in nat ive diets may provide insight into suitability of domestic animals mod els for providing adequate diets in captive feeding situations, as wel l as help define resource limitations in natural environments. (C) 199 7 Wiley-Liss, Inc.