Medicinal plant exudativory by the Bengal slow loris Nycticebus bengalensis

Abstract

Slow lorises are members of a rare guild of obligate exudativores. Secondary metabolites in their diet have been implicated as contributing to the evolution of both their slow basal metabolism and their venom. No long-term study has yet examined the feeding ecology of the largest of the lorises, the Bengal slow loris Nycticebus bengalensis. We conducted an 18 mo study from June 2008 to December 2010 in Hollongapar Gibbon Wildlife Sanctuary, Assam, India, to investigate whether Bengal slow lorises prefer gum, and whether there is any evidence of secondary metabolites in their diet. We detected the lorises along line transects using existing trails and followed each animal as long as possible, recording selected behaviours via focal instantaneous sampling. We recorded 629 feeding incidents during 270 night walks. We found that up to 80.9% of feeding bouts were of plant exudates, followed by bark, floral parts, insects, fruits, and tender (i.e. immature) leaves. Within the plant exudate category, 5 species were consumed in 71% of the total exudate feeding bouts: Terminalia chebula, Mesua ferrea, T. arjuna, Ficus hispida and Dillenia indica. These species all have high medicinal value and are commonly used by the local communities for traditional medicinal purposes. Absorption of secondary metabolites from these plants may explain unusual healing patterns observed in wild slow lorises, but lacking in lorises held in captivity. Their dietary affinity towards medicinal plants could explain patterns of use of slow lorises within the traditional medicine trade in the Indo-Chinese region.