Importance of Plant Galls to the Diet and Nutrition of a Frugivorous Primate, <i>Varecia variegata</i>

Abstract

Frugivorous primates may consume unusual food items, such as plant galls, to meet their nutritional requirements; yet, the contributions of these dietary components to their diet, nutrition requirements, and energy intakes are still unclear. We documented the importance of plant galls in these aspects for black-and-white ruffed lemurs (Varecia variegata) in a Malagasy rainforest. Using daily observation data of lemur foraging and nutritional analyses of their consumed items, we measured (1) the proportion of galls in their diet, (2) the rate at which they acquire nutrients and energy from galls compared to other food items, and (3) the changes in their diet patterns and acquisition of nutrients and energy with the consumption of galls. We also investigated whether they are more likely to consume fruits on trees with galls and characterized whether galls have similar characteristics as fruits. We found that plant galls constituted 12.96% of the lemur feeding occurrences; and on some days, lemur diets comprised galls only. Also, the lemurs acquired from galls higher protein than any other food items and higher sugar, fiber, and energy than leaves, but lower lipid than fruits and similar nutrients and energy as from flowers. The addition of galls in their diet significantly reduced their consumption of ripe fruits on a daily basis and increased the acquisition of protein, sugar, fiber, and energy. Also, lemurs were more likely to consume fruits on trees with galls than expected, likely due to similarities in color and nutrient components between galls and fruits in this system. These findings enhance our understanding of the nutritional needs and food selection behavior of primate frugivores. Such knowledge has implications for developing strategies to maintain primate populations in their natural environments and potentially to ensure the welfare of captive animals in ex-situ conservation settings.