Judul: Foraging skill learning of immature Tapanuli orangutans at Camp Mayang Research Station, North Sumatra.
Abstrak: One of the most important skills to learn during postnatal development period is foraging skill. It is apply to orangutans’ need in their complex foraging niche, broad diets, and highly fluctuating food availability in the natural habitat. Study about this behavior in Tapanuli orangutans (Pongo tapanuliensis) has never been described yet. Therefore, the aim of this study was to observe the foraging skill learning of immature Tapanuli orangutans at Camp Mayang Research Station, North Sumatera. I did the observation with focal animal sampling of immature individual and its mother as references. Data analysis was performed using Kruskal Wallis test and corrected with False Discover Rate. I found that the infant had high independency on social feeding behavior toward its mother, high similarity of diet repertoires and food processing steps with the mother. Moreover, the infant still depended on the mother to find feeding patches and travelling through the forest. The results indicated that foraging skill learning of infant Tapanuli orangutan happened vertically, from the mother to the infant.
Keyword: diet repertoires, food processing steps, Pongo tapanuliensis, postnatal development, social feeding behavior

Judul: Perilaku Anak Orangutan (Pongo pygmaeus pygmaeus) di Pusat Primata Schmutzer, Taman Margasatwa Ragunan dan Taman Safari Indonesia
Abstrak: aaaaaOne of the important component in infant development of the orangutan is the parent. In the exsitu habitat, some evidences of infants have been rejected by their parents were identified. The problem arousing from this condition was how to take care of orphan orangutan infants that are refused by their parents or the disability of parents in taking care of their infants. The aim of the research was to determine the difference of behavior development between infants nursed by their parents and those nursed by people. The research has been conducted at the Schmutzer Primate Center (PPS), Ragunan Zoological Park, Jakarta and Indonesia Safari Park (TSI), Bogor, from September 2007 to April 2008. The objects of the research were eight orangutan infants from Kalimantan (Pongo pygmaeus pygmaeus); their age were 1 month, 6 months, 1 year, and 2 years old. Focal animal and ad libitum sampling methods were used on the research. The observation was done on the development of orangutan infant behavior which based on resting, moving, feeding, playing, social, agonistic, and self care. Results indicated that based on the activity pattern, only Chelin (PPS3) and Kano (PPS4) were correspond to general activity pattern in natural habitat. Behavior development of moving and playing increased as orangutan infants grew up. Feeding behavior development did not show neither increase or decrease. However, social behaviour development decreased as they grew up. These findings indicated that the behavior development of moving and playing of orangutan infants in PPS nursed by their parents is better than those nursed by people, while, the development of social and feeding behavior of infants in PPS nursed by people is better than those nursed by their parents.
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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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