Citation: Ganzhorn, J.U.; Ratovonamana, Y.R.; Rother, M.; Giertz, P.; Andrews, C.A.; Baumann, S.; Bohr, Y.E.-M.B.; Kappeler, P.M.; Montero, B.K.; Pommerening-Röser, A.; et al. Nutritional and Possible Pharmaceutical Aspects of Tree Exudates Eaten by Lemurs of Madagascar’s Dry Forests. Separations 2023, 10, 575. https://doi.org/10.3390/ separations10110575 Academic Editor: Victoria Samanidou Received: 1 November 2023 Accepted: 14 November 2023 Published: 18 November 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). separations Article Nutritional and Possible Pharmaceutical Aspects of Tree Exudates Eaten by Lemurs of Madagascar’s Dry Forests † Jörg U. Ganzhorn 1, * , Yedidya R. Ratovonamana 1 , Melina Rother 1,2 , Peggy Giertz 1 , Curswan A. Andrews 3 , Sabine Baumann 1 , Yvonne E.-M. B. Bohr 1 , Peter M. Kappeler 4,5 , B. Karina Montero 1,6 , Andreas Pommerening-Röser 7 , Ute Radespiel 8 , S. Jacques Rakotondranary 1,9 , Oliver Schülke 10 , Kim J. E. Steffens 1 , Sandra Thorén 8 , Gabriele Timmermann 7 and Irene Tomaschewski 1 1 Institute of Systems Biology of Animals, Animal Ecology and Conservation, Universität Hamburg, Martin-Luther-King Platz 3, 20146 Hamburg, Germany; ryrorch@yahoo.fr (Y.R.R.); melina.rother@web.de (M.R.); peggy.giertz@gmail.com (P.G.); sabine.baumann@uni-hamburg.de (S.B.); yvonne.bohr@onenetbeyond.org (Y.E.-M.B.B.); b.karina.montero@gmail.com (B.K.M.); jacques.rak@gmail.com (S.J.R.); irene.tomaschewski@uni-hamburg.de (I.T.) 2 Medac Gesellschaft für Klinische Spezialpräparate mbH, Abteilung Pharmacovigilance, Theaterstraße 6, 22880 Wedel, Germany 3 African Primate Initiative for Ecology & Speciation, Department of Zoology & Entomology, University of Fort Hare, Alice 5700, South Africa; crswnandrews@gmail.com 4 Behavioral Ecology and Sociobiology Unit, German Primate Center–Leibnitz Institute of Primatology, Kellnerweg 4, 37077 Göttingen, Germany; pkappel@gwdg.de 5 Department Sociobiology/Anthropology, University of Göttingen, Kellnerweg 6, 37077 Göttingen, Germany 6 Institute of Evolutionary Ecology and Conservation Genomics, University of Ulm, 89081 Ulm, Germany 7 Institute of Plant Science and Microbiology, Department of Microbiology and Biotechnology, Universität Hamburg, Ohnhorststrasse 18, 22609 Hamburg, Germany; andreas.pommerening@uni-hamburg.de (A.P.-R.); gabriele.timmermann@uni-hamburg.de (G.T.) 8 Institute of Zoology, University of Veterinary Medicine Hannover, Foundation, Buenteweg 17, 30559 Hannover, Germany; ute.radespiel@tiho-hannover.de (U.R.); thorensandra@gmail.com (S.T.) 9 Département d’Anthropologie, Université d’Antanananriovo, Antananarivo P.O. Box 906, Madagascar 10 Department for Behavioral Ecology, University of Göttingen, Kellnerweg 6, 37077 Göttingen, Germany; Oliver.Schuelke@biologie.uni-goettingen.de * Correspondence: joerg.ganzhorn@uni-hamburg.de † In memoriam of Fabien Génin and Judith Masters. 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. Keywords: plants; gum; resin; antibacterial effects; strepsirrhine primates; self-medication; Microcebus; Phaner Separations 2023, 10, 575. https://doi.org/10.3390/separations10110575 https://www.mdpi.com/journal/separations