Judul: The Sleeping Site Selection of Sulawesi Black- Crested Macaque (Macaca nigra Desmarest 1822) in Tangkoko, North Sulawesi
Abstrak: Monyet jambul hitam Sulawesi (Macaca nigra) merupakan salah satu dari 7 spesies monyet endemik Sulawesi. Populasi M. nigra hanya dapat ditemui di hutan Provinsi Sulawesi Utara dan pulau-pulau kecil di sekitarnya. Persebaran yang sangat terbatas dan tren populasi yang menurun membuat status konservasi M. nigra masuk dalam kategori Kritis (Critically Endangered). Penelitian ini bertujuan untuk menginvestigasi strategi pemilihan lokasi tidur pada Macaca nigra di Kesatuan Pengelolaan Hutan Konservasi (KPHK) Tangkoko, Sulawesi Utara, Indonesia. Penelitian mengenai pemilihan lokasi tidur penting dilakukan untuk memberikan gambaran mengenai proses adaptasi dan strategi bertahan hidup dari suatu spesies. Saat tertidur, kondisi tubuh dalam keadaan tak sadarkan diri dan rentan diserang oleh predator. Lokasi tidur harus dipilih dengan sangat hati-hati untuk memaksimalkan penggunaan energi dan waktu, serta mengurangi resiko ancaman seperti predator. Dua grup monyet jambul hitam Sulawesi (M. nigra) yang telah terhabituasi diamati selama sembilan bulan dimulai dari September 2020 hingga Juni 2021 dengan total waktu pengamatan selama 187 hari atau 2.251 jam. Selama penelitian, M. nigra tercatat menggunakan 20 lokasi tidur yang berbeda dengan lima lokasi di antaranya dipakai oleh kedua grup. Macaca nigra menghindari tidur di lokasi yang sama dengan malam sebelumnya. Dua kali perjumpaan dengan predator (Python reticulatus) terjadi di dekat lokasi tidur tetapi tidak ada monyet yang dimangsa selama penelitian berlangsung. Macaca nigra menggunakan 58 pohon tidur dari 13 spesies tumbuhan. Sebanyak 79% (n=46) dari pohon tidur merupakan jenis pohon yang dikonsumsi oleh M. nigra. Secara umum, spesies ini memilih tidur di pohon dengan ketinggian 30 meter, diameter besar, dan kanopi rimbun agar dapat melindungi diri dari predator, menampung seluruh anggota grup, dan melindungi dari cuaca buruk. Jarak rata-rata antara pohon tidur dan pohon pakan yaitu 203 meter di pagi hari dan 127 meter di sore hari. Macaca nigra mengeluarkan suara loud call secara intens pada jam 05.00 – 07.00 dan jam 16.00 – 18.00 WITA. Loud call berperan sebagai sinyal komunikasi kepada grup monyet lainnya agar bisa menghindar dari kompetisi intergrup. Hasil penelitian ini menunjukkan bahwa M. nigra memilih lokasi tidur sebagai strategi untuk menghindari predator, mendapatkan makanan, dan menghindari kompetisi dengan grup lain. Penelitian bermanfaat untuk memberi gambaran yang lebih luas akan preferensi habitat dan strategi yang dilakukan M. nigra untuk kelangsungan hidupnya. Hasil penelitian ini dapat menjadi rekomendasi untuk menentukan titik lokasi patroli, pemasangan kamera jebak, serta acuan untuk survei kelayakan lokasi pelepasliaran.
Keyword: Macaca nigra, monyet jambul hitam Sulawesi, pemilihan lokasi tidur

Judul: Habitat characteristics and population size of black crested macaque (Macaca nigra Desmarest, 1822) in several habitat types in Tangkoko Nature Reserve, North Sulawesi
Abstrak: This study was conducted in Tangkoko Nature Reserve Bitung-North Sulawesi from July to August 2009. The objectives of this study were to identify habitat characteristics of Macaca nigra including physical component, vegetation structure, canopy cover, water availability, food availability, and to assess the population size in Tangkoko Nature Reserve. Vegetation analysis were made in five habitat types including beach forest, primary lowland forest, secondary lowland forest, transitional (ecotone) forest and burned forest. Fifty seven plant species from 29 families including seedling, sapling, pole, and tree were identified during this study. Population size was determined by direct encounter. Trees from family Anacardiaceae, Moraceae, Myrtaceae, Verbenaceae, and Clusiaceae were dominant in study area. The highest Diversity Index was found in lowland transitional forest. Similarity Index shown that every habitat types had little similarity, the biggest similarity index was found between primary forest and transitional (43.10 %). Canopy stratum C (4 - 20 m) was dominant in the study area. The most complex canopy strata were found in primary forest which had canopy stratum A, B, and C. Canopy cover density in the study area was relatively high with more than 85 % except in burned forest with a canopy cover density of 40.73 %. Macaca nigra more active in location with higher canopy cover density than in areas that have less canopy cover density. The cover was used by Macaca nigra for concealment, sleeping, eating, and resting. Five water resources were recorded in Tangkoko Nature Reserve during this study. Macaca nigra used these water resources as drink water sources, bathing places, reducing heat, and as playground areas. Nineteenth plant species were recorded eaten by Macaca nigra and fruit was their primary diet. During the study, nine groups of Macaca nigra were found. Four group (Rambo I, Rambo II, Rambo III, and Pantai Batu) intensively observed to know its population structure, sex ratio, and population size. Population size of these groups was 221 individuals. Based on the analysis with ArcView 3.3, the study site covering an area of 686.456 ha. Group size was 14 – 72 individuals/group. The group density was 0.58 groups/km2 and population density was 32.2 ind/km2. Ecotourism activities, hunting and habitat pressure (forest fire and Ilegal logging) are the main threats for Macaca nigra sustainability.
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Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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