RESUMEN
Long-tailed macaque (Macaca fascicularis is one of the most common primates in Indonesia. In Sleman, Yogyakarta, Indonesia, the long-tailed macaque is habituated in Merapi Forest. The study aims to estimate the long-tailed macaque population and re-identification of groups. Moreover, we will observe the social structures that probably changed because of the interruption of interaction with visitors after the closure of the Tlogo Muncar area during the COVID-19 pandemic. The estimation population study was done using the concentration method. The long-tailed macaque group in Tlogo Muncar consists of three groups: Waterfalls, Mosque, and Joglo Trubus. The study was also identifying the alpha male of each group. The dataset obtained was processed using Microsoft Excel and analyzed descriptively. The results show that the estimated long-tailed macaque population in Tlogo Muncar area is 282 individuals. Alpha male identification of each group found alpha males in the Waterfall Group characterized by a lump on the left eyelid and a wound on the left hand. The alpha male of the Mosque Group is marked by a lump on his left eyelid with maxillary prognathism, while the alpha male of the Joglo Trubus Group has transverse scratches on the nose. The results showed an increase in the long-tailed macaque population in Tlogo Muncar area from 201 individuals in 2021 to 282 individuals in 2022. The increase of ecological pressure perhaps caused the rise in population number in 2022 during the closure of the area, to which the adult female responded by increasing their reproduction rate. The reopening of Tlogo Muncar after the Covid-19 pandemic has increased feed availability and attracted monkeys to forage outside the forest.