Nutritional and Possible Pharmaceutical Aspects of Tree Exudates Eaten by Lemurs of Madagascar’s Dry Forests

Abstract

Gums produced by trees after injuries are valuable food resources for several primate species. Yet, information on the chemical characteristics of gum is scant and inconsistent. We use gums consumed by lemurs (strepsirrhine primates of Madagascar) as an example to illustrate their possible nutritive and pharmaceutical properties. Exudates from 45 tree species of the dry forests of Madagascar contained 0.38–23.29% protein, 0.46–65.62% sugar, and 0.39–11.86 kJ/g of energy in dry matter. Exemplified by the lemur species Microcebus griseorufus, gum consumption increased with increasing sugar and energy content but was unrelated to protein. But lemurs also fed on gum with very low protein and energy content, suggesting that these exudates were consumed for other reasons. Disk diffusion tests with exudates from five out of 22 tree species consumed by lemurs showed antibacterial activity against Micrococcus spp. and/or Staphylococcus aureus. Exudates with antibacterial activity had lower protein, sugar, and energy contents than samples without antibacterial properties. GC-MS analyses revealed several components with antimicrobial effects that would have the potential for self-medication. This might explain the consumption of gum with very low nutritive value. Possible medicinal effects of tree exudates deserve further attention in view of their pharmaceutical applicability for animals and humans alike.