Population Estimate of Long-Tailed Macaques (Macaca fascicularis) on Tinjil Island

Tinjil Island was established as a Natural Habitat Breeding Facility for long-tailed macaques (Macaca fascicularis) in 1997. Between February 1998 and January 2007, 603 (61 males and 542 females) simian retrovirus (SRV) free long-tailed macaques were introduced to the island on the south coast of West Java and function as a primate resource and conservation program. To date, 3256 progenies have been harvested and used as the animal model. Therefore, it is necessary to survey the current population of the long-tailed macaques to evaluate whether the population is still under the island’s carrying capacity. This research aims to identify the population estimate of long-tailed macaques currently occupying the island. The observation was conducted in July 2021 using line transect sampling starting from 07.00 AM and 01.00 PM. Twelve observations were conducted during the study using CD and ES transects. CD (Chuck Darsono) and ES (Emil Salim) are the two longest trails on the island and represent the names of the people who initiated the captive breeding of Tinjil Island. The estimated group density of the long-tailed macaques on Tinjil Island is 13.46 groups/km2, while the estimated population density is 111.04 individuals/km2. The population estimated on the island is 627.38±23.53 individuals. The number indicates that the population is still under carrying capacity

Population Density of Kloss’s Gibbon (Hylobates klossii) at Bojakan Resort, Siberut Island, West Sumatra: KEPADATAN POPULASI BILOU (Hylobates klossii) DI RESORT BOJAKAN, PULAU SIBERUT, SUMATERA BARAT

Kloss’s gibbon (Hylobates klossii) is endemic primate to the Mentawai Islands of the West Sumatra, and currently categorized as Endangered according to IUCN Red List in 2008. The latest population information on Siberut Island is incomplete and not comprehensive yet. Assessment of population was used as a base in determining the conservation strategies. This study aimed to identify the Kloss’s gibbon population that includes population distribution, individual and group density, group size, and group composition. This research was conducted in Bojakan Resort, Siberut National Park, Siberut Island, Mentawai Islands, West Sumatra. Surveys for primates were carried out between November 2018 and Januari 2019. Following previous primate surveys and general recommendations, this study used line transect sampling. Total Kloss’s gibbon individuals found were 77 individuals with 25 groups. Average individual density was 12,8 individuals km2, group density was 4,2 groups km2, and group size was 3,08 individuals group. Kloss’s gibbon populations was affected by disruption of human activity. Kloss’s gibbon density in Bojakan Resort was higher compared to previous studies on Siberut Island. The percentage of Kloss’s gibbon groups that have a group size of more than two individuals was higher than the group of two individuals, indicating that forests in Bojakan Resort was abble to support the Kloss’s gibbon population. There were many groups that have at least one or more offspring, a good sign that regeneration progress was still ongoing. Monitoring and patrolling by National Park is needed to ensure the existence of the Kloss’s gibbon population in that area.   Keywords: endemic primate, kloss’s gibbon, line transect sampling, monogamyBilou (Hylobates klossii) merupakan satwa primata endemik Kepulauan Mentawai, Sumatera Barat dan ditetapkan sebagai satwa primata dengan status terancam/genting (endangered) berdasarkan kategori IUCN (International Union for Conservation of Nature and Natural Resources) tahun 2008. Saat ini, informasi populasi bilou terbaru di Pulau Siberut belum diketahui secara lengkap dan menyeluruh. Penilaian terhadap populasi dijadikan sebagai landasan dalam menentukan strategi konservasi. Penelitian bertujuan mengidentifikasi populasi bilou yang meliputi distribusi populasi, kepadatan individu, kepadatan kelompok, ukuran kelompok, serta komposisi kelompok. Penelitian dilaksanakan di Resort Bojakan, Taman Nasional Siberut, Pulau Siberut, Kepulauan Mentawai, Sumatera Barat pada bulan November 2018 sampai Januari 2019. Pengamatan dan pengukuran parameter populasi bilou dilakukan dengan metode line transect sampling. Total perjumpaan dengan bilou sebanyak 77 individu dengan jumlah 25 kelompok. Nilai kepadatan individu 12,8 individu/km2, dan kepadatan kelompok 4,2 kelompok/km2. Rerata ukuran kelompok bilou di Resort Bojakan 3,08 individu/kelompok. Keberadaan populasi bilou di Resort Bojakan dipengaruhi akibat adanya gangguan aktivitas manusia. Kepadatan populasi bilou di Resort Bojakan lebih tinggi dibandingkan dengan penelitian-penelitian sebelumnya di wilayah Pulau Siberut. Persentase kelompok bilou yang memiliki ukuran kelompok lebih dari dua individu lebih tinggi dibandingkan kelompok dengan jumlah dua individu, yang menandakan kawasan Taman Nasional Siberut terutama di Resort Bojakan mendukung pertumbuhan populasi bilou. Proses regenerasi bilou masih terus berlangsung karena jumlah kelompok yang memiliki minimal satu keturunan atau lebih masih cukup banyak. Pemantauan dan patroli oleh pihak Taman Nasional diperlukan untuk memastikan keberadaan populasi bilou di Resort Bojakan.   Kata kunci: primata endemik, bilou, metode garis transek, monogam