Judul: Activity  Budget and Diet in Sumatran Orangutan (Pongo abelii) at Soraya Research Station, Aceh
Abstrak: The Sumatran orangutan (Pongo abelii) is categorised as critically endangered by the International Union for Conservation of Nature (IUCN). Orangutan existence in nature is increasingly threatened due to poaching and high rates of habitat deforestation. Understanding the daily activities and foraging behaviour of orangutans and their relationship to food availability can provide information on how orangutans can adapt to environmental changes in their habitat . Soraya Research Station (SRS) is a research station located in The Leuser Ecosystem and is a natural habitat for the Sumatran orangutan. However, information regarding the relationship between food availability and its relation to the daily activities and diet of orangutans in this location has not been reported. This study aims to observe orangutans daily activities and diet composition in SRS and their relationship with food availability. We observed the activity budget and diet from October 2021 until March 2022 at the Soraya Research Station (SRS). SRS is located in Pasir Belo Village, Sultan Daulat District, Subulussalam City, Aceh Province (N 02o 55’414”-E97o55’731”). The daily activity and feeding behaviour observation was conducted used focal animal sampling methods and instantaneous method with an interval of two minute. All data collected followed the standard collection of orangutan data in the field. The collection of phenological data and the food availability was carried out using the existing phenological plots at the research station. The number of phenological plots observed every month was 20 plots with a plot size of 20 x 20 m (0.8 Ha), estimated to consist of 550 trees. The phenological phases observed included young leaves, flowers, fruit, and ripe fruit. The phenological data and annual fruit availibility from 2017-2022 were also analyzed. Later, our data were analysed at the Laboratory of Biosystematics and Animal Ecology, Department of Biology, IPB University. The results show that the FAI index at SRS were low, only reaching 1.01%. Daily activity observations were carried out on five individual Sumatran orangutans in SPS, consisting of one adult female, two flanged males, one unflanged male, and one juvenile male in total 648 hours observations. Resting is the activity with the highest percentage (48%), followed by foraging (22.5%) and moving (21.8%). Low fruit availability affects Sumatran orangutans in SPS to have a high percentage of resting activity. The high percentage of rest activity aims to limit their energy expenditure. Analysis of diet composition showed that Sumatran orangutans in SPS consumed the highest percentage of bark (40.6%), followed by fruits and other plants (28.9% and 15.6%, respectively). The high consumption of bark by orangutans can be a fallback food in SPS and is thought to be a form of adaptation when fruit is scarce. The uniqueness of the SRS’s ecology characteristic might not be suitable for orangutans to live. Nevertheless, SRS can be considered a connected forest between the primary forest (Leuser National Park) and the surrounding belt forest area and other used forest areas. It can be considered a natural habitat for the Sumatran orangutans to meet their daily roaming area. The study on daily activities, population and phenology in SRS needs to be continued.
Keyword: Orangutan sumatra, Aktivitas harian, Fenologi, FAI, Komposisi pakan, Adaptasi

Judul: Spatial Distribution of Sumatran Orangutan Activities (Pongo abelii Lesson, 1827) in Rawa Singkil Wildlife Reserve Area, Aceh Province
Abstrak: Populasi orangutan sumatera terus mengalami penurunan salah satunya disebabkan oleh permasalahan habitat. Upaya pembinaan habitat penting dilakukan untuk mendukung penaikan populasi orangutan. Mengingat orangutan merupakan satwa yang sulit dijumpai secara langsung, maka penelitian terkait jejak aktivitas orangutan sumatera penting untuk dilakukan. Penelitian ini bertujuan mengidentifikasi jenis-jenis jejak aktivitas orangutan sumatera, mengetahui bentuk sebaran spasial jejak aktivitas orangutan sumatera, dan menganalisis hubungan antara jejak aktivitas dengan karakteristik habitat orangutan sumatera di kawasan Suaka Margasatwa Rawa Singkil. Pengambilan data dilakukan pada petak pengamatan berukuran 1.000 x 1.000 meter, pada petak tersebut dibuat 4 jalur dengan menggunakan metode line transect. Jenis jejak aktivitas orangutan sumatera yang dijumpai yaitu sarang dan bekas pakan. Jenis jejak berupa sarang lebih banyak ditemukan. Bentuk sebaran spasial jejak aktivitas orangutan sumatera adalah mengelompok dengan nilai Ip sebesar 0,55. Jejak aktivitas orangutan sumatera banyak ditemukan pada hutan rawa primer dengan topografi datar (0 – 8%), jauh dari pemukiman (>8000 m), dan dekat dengan sumber air (<1000 m)., The population of Sumatran orangutans continues to decline, one of which is caused by habitat problems. Efforts to foster habitat are important to support the increase in the orangutan population. Given that orangutans are animals that are difficult to find in person, it is important to conduct research on the traces of Sumatran orangutan activity. This study aims to identify the types of Sumatran orangutan activity tracks, determine the spatial distribution of Sumatran orangutan activity tracks, and analyze the relationship between activity tracks and Sumatran orangutan habitat characteristics in the Rawa Singkil Wildlife Reserve area. Data collection was carried out on an observation plot measuring 1,000 x 1,000 meters, in that plot 4 lines were made using the line transect method. The types of traces of Sumatran orangutan activity found were nests and former feed. Types of traces in the form of nests are more commonly found. The form of the spatial distribution of Sumatran orangutan activity traces is clustered with an Ip value of 0.55. The traces of Sumatran orangutan activity are mostly found in primary swamp forest with flat topography (0 – 8%), far from settlements (>8000 m), and close to water sources (<1000 m).
Keyword: Orangutan sumatera, Suaka margasatwa rawa singkil, Sebaran spasial

Judul: Penentuan Nilai Eigen dan Vektor Eigen dari Matriks Tridiagonal 2-Toeplitz dengan Pendekatan Polinomial Chebyshev
Abstrak: The eigenvalues and eigenvectors of a matrix can be determined by finding its characteristic polynomials. The characteristic polynomials of a tridiagonal 2-Toeplitz matrix is shown to be closely connected to polynomials which satisfy the Chebyshev recurrence relationship. If the order of the matrix is odd, then the eigenvalues are found explicitly in terms of the Chebyshev zeros and the eigenvectors are found in terms of the polynomials satisfying the recurrence relationship. For even ordered matrices, the situation is more complicated. The problem in these cases is that although the Chebyshev recurrence formula is still applied, its initial values are not generating Chebyshev polynomials
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