Feeding Ecology and Regurgitation/Reingestion Behavior of the Critically Endangered Indri indri in the Maromizaha Protected Area, Eastern Madagascar

Deforestation around the world is a major threat to primates. Understanding primate species' habitat and dietary requirements is critical in creating effective conservation management plans. Indri indri, a Critically Endangered lemur species from Madagascar's eastern rainforests, has a diet dominated by leaves. We conducted a long-term study of I. indri feeding behavior in Maromizaha Protected Area by collecting over 4000 hours of observational data on six habituated groups from 2011-2019. Our specific objectives were to: 1) characterize the habitat of the study groups, 2) identify the availability of leaves, fruits, and flowers, 3) provide a description of the general diet of I. indri including variation therein, 4) describe a newly observed regurgitation and re-ingestion behavior, and 5) perform phytochemical analyses of the leaves and fruits which were likely causing the regurgitation and re-ingestion. Areas of similar topography generally had similar forest structure. Phenological monitoring of 18 botanical plots located in the I. indri territories showed that the availability of young leaves, fruits, and flowers varied seasonally and was impacted by damage from a cyclone in February 2012. All groups were mainly folivorous but showed some annual variation in the proportion of the diet devoted to fruit. Leaves and fruits consumed before regurgitation and re-ingestion was observed contained hydrolysable and condensed tannins, which may explain the presence of the behavior. In conclusion, this study provides important natural history data on the behavioral flexibility of I. indri to inform their conservation.