Effects of food availability and its seasonal changes on the dietary habits of wild silvery lutungs (Trachypithecus cristatus) in a coastal forest in west Sumatra, Indonesia

Abstract

The dietary composition of primates is often affected by the availability of food, as well as seasonal variations within their habitat. This study presents quantitative data on the feeding behavior of wild silvery lutungs (Trachypithecus cristatus) inhabiting a coastal forest in West Sumatra, Indonesia. This research emphasizes the relationship between food availability and the way this changes by season. Feeding strategies of these primates was also examined. Feeding behavior of a group of wild silvery lutungs was observed for 12 months from August 2018 to July 2019, with a total observation time of 482 hours. We recorded 74 items from 37 different plant species that were included in the lutungs’ diet. Nineteen out of 37 plant species comprised > 1% of the lutung’s annual diet. They can therefore be considered the main plant food sources for the lutungs. The lutungs mainly fed on young leaves (68.3%). However, during certain months, both ripe and unripe fruit formed a major part of their diet. Plant part-based analyses showed a negative correlation between the availability of young leaves and ripe fruit feeding. Plant species-based analyses revealed few significant positive relationships between the feeding percentages of the main dietary items (mainly young leaves) and their availability. This implies that young leaves and ripe fruit were both the preferred and the fallback foods. This also indicates that lutung activity, ranging patterns, and activity at the study site are affected mainly by food distribution and availability. Further research is needed to increase the understanding of Asian colobine feeding strategies, feeding patterns, and food resource characteristics.