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: Variasi Geografis dan Lingkungan dalam Anggaran Aktivitas dan Kebiasaan Makan Orangutan di Sumatera
Abstrak: Food availability is a major determinant of primate activity, home range use, group size, and population parameters. Food environments of captive animals, for example, would much better than the wild populations. There is a regional variation in the wild's food environments, mainly due to physical conditions and forest structure. This study analyzed the impact of differences in geographic and environmental variables and forest types on the behavioral and social aspects of orangutans in Sumatra. This study also compared the orangutans' activity between captive and wild conditions. Altitude, mean temperature, and annual rainfall of six wild orangutans in Sumatra study sites ranged 0 - 2067 m, 18 - 31 oC, and 1125 - 3967 mm, respectively. There were no significant differences in activity budgets, dietary habits, home ranges, daily travel distances, and group composition of the orangutans among forest types. None of the geographical and environmental variables were correlated with the behavioral and social aspects. Furthermore, there were no significant differences in orangutan activities between wild and captive, except feeding activity. Besides the small number of study sites, the lack of variation in behavioral and social aspects implied the orangutans' conservative nature., Ketersediaan makanan merupakan penentu utama dari aktivitas primata, penggunaan wilayah jelajah, ukuran kelompok, dan parameter populasi. Lingkungan makanan hewan penangkaran, misalnya, jauh lebih baik daripada populasi liar. Bahkan pada populasi liar, terdapat variasi regional dalam lingkungan makanan, terutama karena kondisi fisik dan struktur hutan. Studi ini menganalisis dampak perbedaan variabel geografis dan lingkungan, dan tipe hutan terhadap aspek perilaku dan sosial orangutan. Studi ini juga membandingkan aktivitas orangutan antara kondisi penangkaran dan liar. Ketinggian, suhu rata-rata, dan curah hujan tahunan dari enam lokasi penelitian orangutan liar di Sumatera berkisar 0 - 2067 m, 18 - 31 oC, dan 1125 - 3967 mm. Tidak ada perbedaan yang signifikan pada anggaran kegiatan, pola makan, wilayah jelajah, jarak perjalanan harian dan komposisi kelompok orangutan di antara tipe hutan, dan tidak ada variabel geografis dan lingkungan yang berkorelasi dengan aspek perilaku dan sosial. Selain itu, tidak ada perbedaan yang signifikan antara aktivitas orangutan liar dan penangkaran, kecuali aktivitas makan. Selain sedikitnya lokasi penelitian, minimnya variasi aspek perilaku dan sosial menunjukkan sifat konservatif orangutan.
Keyword: activity budget, dietary, forage tree, nest

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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