Orangutan is the Asian representative of the great apes. Its present range is confined to dwindling areas on the islands of Sumatera (Pongo abelii) and Borneo (Pongo pygmaeus) (Rijksen & Meijaard, 1999). Orangutans are arboreal (Rijksen, 1978; Galdikas, 1978), frugivorous (MacKinnon, 1974) and live semi-solitary in fission- fusion societies (Delgado & van Schaik, 2000). Ketambe, one of the major orangutan sites, supports a population density of 3-5 ind/km2 . Ketambe Research Center, which is based in Gunung Leuser Ecosystem, was run since early 1970. There are at least six families of orangutans living in the research areal of 450 ha, including the offspring of the ex rehabilitation orangutans. Orangutans in this area have been studied since 1971, where many behavioral and ecological studies have been conducted.. One of the most important studies identified matrilines within Ketambe based on genetic analysis (Atmoko, 2000) Female orangutans in Ketambe tend to be philopatric which means that they remain in their natal or birth groups. This condition is the result of intense competition among individual orangutans over food patchs because they often form dominance relations when meeting in the same food patch. Dominan ranking of ex-rehabilitation orangutans, based on a liniear index of responses in the context of displacement at a food patch, tends to be lower than those of wild orangutans. Orangutans travel and forage to find food patches within their habitat. By using software GIS Arc View 3.3, Day Journey Length (DHL) adult females including ex-rehabilitation female orangutan ex-rehabilitant is known to be 37-2.106 meters with an average between 437-795 meter. The matrilinial relationship between individuals influence each other in foraging and competition to form home ranges, especially for females. Orangutans matrilines tend to have overlapping home ranges between 46,66% - 97,07%).
