Leaf Chemistry and Food Selection by the Common Langur (Presbytis entellus, Dufresne 1797) in Rajaji National Park U.P. India

Abstract

Food selection in folivorous primates has been hypothesised to be correlated with leaf chemistry. To test this hypothesis, a 5- month study on Presbytis entellus was carried out in a moist deciduous forest in the Rajaji National Park, U.P. Two indices of food selection were estimated: percent time spent feeding on the food item, and selection ratio. The former was estimated from group scan data collected from one study group for six days each month. The selection ratio for each item was estimated as a ratio of time spent feeding to availability. Food availability was estimated from vegetation sampling, which covered 6% of the home range of the study group, and phenology data in the study area. Crude Protein (CP), Acid Detergent Fibre (ADF) and Tannins in mature and young leaves of 12 major food species were estimated in the laboratory. Food selection was positively correlated with CP in winter and with ADF in both seasons. It was also correlated with CP/ADF ratio, but to a lesser extent than the best predictor in winter and spring. Selection ratio did not have any correlation with CP in two seasons and only a weak correlation with ADF» It is very likely that the inclusion of other factors such as micro-nutrients, condensed tannins and digestibility might give a better prediction of food selection.