Judul: Distribution dan population density of silvery langur (Trachypithecus cristatus) in a mangrove forest, Handil Baru Village, East Kalimantan
Abstrak: Lutung kelabu (Trachypithecus cristatus) merupakan salah satu primata dalam famili Cercopithecidae yang tersebar di Kalimantan dan Sumatera. Lutung kelabu menempati daerah pesisir mangrove dan tepi pantai. Saat ini, lutung kelabu di Kalimantan nyaris kehilangan habitat dikarenakan adanya perubahan fungsi lahan. Kelurahan Handil Baru memiliki area mangrove seluas 64 ha yang ditempati oleh lutung kelabu. Informasi mengenai keberadaan lutung kelabu pada kawasan mangrove masih sangat sedikit dibandingkan dengan jenis habitat lainnya sehingga penting untuk dilakukan penelitian. Penelitian ini bertujuan untuk mendeteksi persebaran, mengestimasi kepadatan populasi, dan mendeteksi penggunaan strata pohon serta mengidentifikasi jenis pakan lutung kelabu. Penelitian dilakukan pada bulan Mei-Agustus 2019. Kepadatan populasi dihitung melalui pengamatan langsung dengan metode Concentration Count sedangkan distribusi lutung dianalisis menggunakan software ArcGIS ver 10.4. Pengamatan dengan menggunakan strata pohon dibagi menjadi 4 yaitu tajuk atas, tajuk tengah, tajuk bawah dan terestrial. Metode pengamatan dengan scan sampling dengan interval 5 menit, adapun aktivitas yang dicatat meliputi perilaku harian seperti makan, istirahat, berpindah tempat, bersembunyi dan aktivitas sosial. Pengambilan data jenis tumbuhan pakan lutung kelabu dengan mengamati secara langsung. Pengumpulan data spesies pakan dengan pengamatan secara langsung. Spesies pakan yang tidak teridentifikasi di lapangan selanjutnya akan dikoleksi dengan membuat herbarium. Identifikasi spesimen yang dikoleksi dilakukan di Laboratorium Sistematika Tumbuhan FMIPA Universitas Mulawarman. Pada penelitian ini ditemukan tiga kelompok lutung kelabu pada kawasan mangrove Kelurahan Handil Baru yang tersebar di Handil Baru Muara, Sungai Raden dan Sungai Mantri. Kepadatan populasi di Handil Baru Muara sebesar 6,63 individu/ha, Sungai Raden 2,65 individu/ha dan Sungai Mantri 0,72 individu/ha. Jumlah individu setiap kelompok bervariasi yaitu Handil Baru Muara 24 individu, Sungai Raden 17 individu dan Sungai Mantri 18 individu. Lutung kelabu lebih banyak menggunakan tajuk tengah dan tajuk bawah dalam aktivitasnya. Kelompok lutung kelabu di Handil Baru Muara memiliki jumlah pakan 22 spesies, di Sungai Raden tujuh spesies dan di Sungai Mantri enam spesies. Kepadatan populasi dipengaruhi oleh fungsi lahan, jumlah individu pada lokasi tersebut serta ketersediaan pakan., Silvery lutung (Trachypithecus cristatus) is one of primate a species in the family of Cercopithecidae which distributed in Kalimantan and Sumatra. It inhabit in coastal areas, mangrove and riparian. Currently, silvery lutung in Kalimantan experienced in habitat loss due to land conversion. Handil Baru Sub District has a mangrove area of 64ha, which inhabit by silvery lutung. Information about silvery lutung in mangrove area is still limited than at other habitat type, therefore there is a needed to conduct observation. This study aims is to detect distribution, estimate population density, and use of tree strata and identify the species as food source of silvery lutung. Observations were held during May-August 2019. The population density was determined using Concentration count, through direct observation and the distribution of this species was analyzed using ArcGIS software version 10.4. Observations of tree strata were divided into 4; upper canopy, middle canopy, lower canopy and terrestrial. Observation method was scan sampling at intervals of 5 minutes, recorded activities include daily activities such as eating, resting, moving around, hiding and social activities. Collecting data on the type of food by observing directly. Unidentified plants were collected by making herbarium. The
Keyword: Hitung konsentrasi, sebaran, pakan, kepadatan populasi, lutung kelabu, Concentration count, distribution, food, population density, silvery lutung

Judul: Dietary Composition and Food Availability of Silvery Lutung (Trachypithecus cristatus) in A Coastal Forest Habitat in West Sumatra, Indonesia
Abstrak: Silvery lutung (Trachypithecus cristatus) is one of the Colobine (leaf-eater) primate species, which has larger distribution among the Trachypithecus genus. Coastal habitat is one of silvery lutungs’ habitat that has unique vegetation with various phenologies among each plant species, thus affect the food availability of silvery lutung. A study about diet and its relationship with food availability is very important to explain the ecological adaption of silvery lutung for each habitat. This study aims to analyze the dietary composition, dietary diversity, and seasonal food availability of each food type. This study was located at Gunung Padang coastal habitat, West Sumatra, Indonesia, where natural vegetation mixed with plantation. The dietary composition was determined by direct observation of one group of silvery lutung (25 individuals) using 10-min-instantaneous scan sampling. Food plant species were identified at Herbarium ANDA, Andalas University. Seasonal food availability was determined through phenological monitoring for 12 months (August 2018 – July 2019) at the study site. Data on dietary composition was feeding percentage for the food plant part and food plant species also expressed the correlation tests between each food plant part, dietary diversity, and food availability. This study found 37 food plant species in silvery lutungs’ diet at Gunung Padang. The main food composition in silvery lutungs’ diet was young leaves (68.3%), followed by unripe fruits (21.1%), mature leaves (5.0%), ripe fruits (2.0%), and flowers (1.1%). Young leaf-feeding had a significant negative correlation with fruit-feeding. Mature leaf-feeding had a significant positive correlation with mature leaf diversity. Young leaf-feeding had a significant negative with young leaf diversity. Young leaf availability had ripe fruit-feeding. The flower of Spathodea campanulata, the young leaves of Homalanthus populneus, and the young fruits of Ficus elastica as the main food plant species of the silvery lutung were directly proportional to their food availability. The dietary composition of silvery lutung in Gunung Padang illustrated that silvery lutung had more options on the food plant part and food plant species. Leaf-feeding affected dietary diversity and food availability in their habitat. The availability of the main food plant species of silvery lutung could support their feeding. Dietary composition, dietary diversity, and food availability are important aspects of silvery lutungs’ survival in their habitat., Lutung (Trachypithecus cristatus) merupakan salah satu spesies primata pemakan dedaunan (Colobinae) yang memiliki distribusi paling luas dengan habitat yang beragam di antara genus Trachypithecus lainnya. Habitat pesisir sebagai salah satu habitat lutung memiliki keunikan vegetasi dengan fenologi yang beragam antar masing-masing spesies tumbuhan sehingga mempengaruhi ketersediaan makanan lutung. Kajian ilmiah tentang diet dan hubungannya dengan ketersediaan makanan sangat penting untuk menjelaskan adaptasi ekologi lutung pada masing-masing habitat. Penelitian ini bertujuan untuk menganalisis komposisi, keanekaragaman dan ketersediaan musiman masing-masing jenis makanan. Penelitian ini berlokasi di habitat pesisir Gunung Padang, Sumatera Barat, Indonesia dimana vegetasi alami bercampur dengan tanaman budidaya. Komposisi makanan diketahui melalui pengamatan langsung terhadap satu kelompok lutung (25 individu) menggunakan 10-min-instantaneous scan sampling. Spesies tumbuhan yang dimakan diidentifikasi di herbarium ANDA Universitas Andalas. Ketersediaan makanan secara musiman diketahui melalui pengamatan fenologi selama 12 bulan (Agustus 2018 – Juli 2019) di lokasi penelitian. Data komposisi makan
Keyword: dietary composition, dietary diversity, feeding activity, food availability, phenology

Judul: Penggunaan Metode Homotopi untuk Menyelesaikan Masalah Nilai Eigen pada Suatu Model Getaran
Abstrak: Most mathematical models of natural phenomena are nonlinear model. One of the nonlinear problems is a problem of vibration which can be considered as an eigen value problem. Here, the nonlinear factor appeared due to the external forces applied to the system. The vibration problem in this study, was solved using the homotopy method. The homotopy method is analytical approach in the nonlinear problems within the series form. The terms of the series were obtained based on a recursive formula in a high deformation. A convergent solution of the series dependent on both the homotopy parameter and the coefficient of nonlinear factors appeared in the model.
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