-1- ABSTRACT Tinjil Island is a semi-natural breeding facility for long-tailed macaques (Macaca fascicularis) managed by Primate Research Center, IPB University, located at the southern of Java Island and surrounded by the Indian Ocean. Long-tailed macaques are considered frugivorous even though they are well- known for their flexible diet. This study aims to analyse the vegetation sup- porting the population of long-tailed macaques. Data were collected from six tracks using square sampling plots with the size of 20 m x 20 m for trees as the main plot, inside the main plot were square subplots consisting of 10 m x 10 m for poles, 5 m x 5 m for saplings, and 2 m x 2 m for seedlings. The Im- portant Value Index (IVI) was calculated for each level of vegetation. Hanjuang (Dracaena elliptica) dominated the seedlings with 29.35%, followed by Kampis (Hernandia peltata) with 18.73%, and Kalapari (Pongamia pinnata) with 13.73%. Hanjuang (Dracaena elliptica) also dominated the saplings with 26.83%, followed by Pancal (Syzygium antisepticum) with 19.19%, and Laban (Vitex pubescens) with 12.30%. The poles were dominated by Ki Cau (Dolichandrone spathacea) as high as 59.28%, while Waru (Thespesia populnea) and Ki Ciat (Ficus septica) dominated at 40.47% and 36.15%, respectively. Kam- pis (Hernandia peltata) dominated the trees with 39.28%, followed by Ki Ara (Ficus glomerata) with 35.56%, and Ki Langir (Dysoxylum amooroides) with 28.70%. Species found on Tinjil Island are mostly Moraceae (9.84%) and Faba- ceae (9.84%), followed by Malvaceae (8.20%), Euphorbiaceae (4.92%), Myr- taceae (4.92%), and Anacardiaceae (4.92%). The vegetation in Tinjil Island supports the livelihood of long-tailed macaques on the island because they have an abundance of food and staple food such as figs to help them fulfil the energy needed to survive and reproduce. Copyright: © 2022, J. Tropical Biodiversity Biotechnology (CC BY-SA 4.0) Research Article Analyses of Vegetation Used by Long-tailed Macaque (Macaca fascicularis Raffles 1821) in Tinjil Island Dyah Perwitasari-Farajallah 1,2,4 ⁎, Hana Intishar Sawitri 1 , Silvy Thiyana 3 , Tommy Langgeng Abimanyu 4 , Entang Iskandar 1,4 , Huda Salahudin Darusman 1,4,5 1)Primate Research Center, Institute for Research and Community Empowerment, IPB University. Jl. Lodaya II no.5 Bogor 16151, West Java, Indonesia. 2)Department of Biology, Faculty of Mathematics and Natural Sciences, IPB University. Jl. Meranti, Kampus IPB Dramaga Bogor 16680, West Java, Indonesia. 3)Department of Forest Resources Conservation and Ecotourism, Faculty of Forestry and Environment, IPB University. Jl. Ulin, Kampus IPB Dramaga Bogor 16680, West Java, Indonesia. 4)Primatology Program, Graduate School, IPB University. Jl. Lodaya II no.5 Bogor 16151, West Java, Indonesia. 5)Department of Anatomy Physiology and Pharmacology, Faculty of Veterinary Medicine, IPB University. Kampus IPB Dramaga Bogor 16680, West Java, Indonesia. * Corresponding author, email: witafar@apps.ipb.ac.id Journal of Tropical Biodiversity and Biotechnology Volume 08, Issue 01 (2023): jtbb70739 DOI: 10.22146/jtbb.70739 INTRODUCTION Long-tailed macaques (Macaca fascicularis Raffles 1821) are primates from the Cercopithecoidea family and are widely distributed in Asia, including Indonesia (Hansen et al. 2022). Based on the IUCN Red List of Threat- Keywords: habitat analysis long-tailed macaque Macaca fascicularis Tinjil Island vegetation analysis Submitted: 25 November 2021 Accepted: 08 November 2022 Published: 17 March 2023 Editor: Ardaning Nuriliani