Preferensi Habitat Bersarang Orangutan Sumatera (Pongo abelii Lesson, 1827) di Kawasan Hutan Batang Toru Kabupaten Tapanuli Utara – Sumatera Utara

Abstract

Habitat degradation and persecution are causes of animals extinction in Indonesia. One of them is Sumatran Orangutan (Pongo pygmaeus abelii Lesson, 1827) that now on the red list of the spesies of International Union for Conservation of Nature (IUCN) as a critically endangered species. Batang Toru Forest (BTF) is one of the last 18 habitat units of Sumatran Orangutan in Sumatera. At the present time, BTF is in initiation process of Collaborative Management Base on Sustainability of Intact Ecosystem Unit figuration. Data and information about Sumatran Orangutan (umbrella spesies of BTF) could accelerate the initiation process. One aspect that could complete the reference of Orangutan is the nesting habitat preferention. The objective of this research is discovered the nesting habitat preferention of Sumatran Orangutan at various habitat in BTF. This research conducted during Oktober-Desember 2008 at YEL-SOCP's research station, in 12,5 km2 west block area of BTF. Equipment that used are GPS, binoculars, measuring tape, camera, camera trap, map, flagging tape, stationary, rope, knife, thermometer, and hygrometer. Secondary data are bioecology of Sumatran Orangutan and general condition of research site which collected by interview and literature observation method. Primary data are Orangutan's nest frequency, which collected by the nest survey method, and the structure and composition of vegetation, which collected by vegetation analysis method. The frequency calculated by dividing the total number of nest that found with the length of the track. The structure and composition of vegetation discovered by Importance Value Index and diagram of profile vegetation. BTF's research site consist of three habitat type; peat swamp forest, upper Dipterocarp forest, and the ecoton. Peat swamp forest characterized by the high abundant of mosses and Nephentes spp., which is gradually decrease in ecoton and in upper Dipterocarp forest. Peat swamp forest has the highest vegetation density, which is also gradually decrease in ecoton and in upper Dipterocap forest. The vegetation species that identified as Orangutan's food resources in peat swamp forest are 7 species, in ecotone are 5 species, and in upper Dipterocarp forest are 4 species. The highest nest frequency found in peat swamp forest (18,7 nests/km track). It is caused by the peat swamp forest provides food resources for Orangutan, such as leaves and tree bark, troughout the year. The stand of peat swamp forest has the highest density than the other habitat, so that the estimation of actual nest frequency in peat swamp forest must be more than 18,7 nest/km track. The nest dissemination in various condition ilustrated the nest habitat preferention concerned with time. During the research, Orangutan build nest in upper Dipterocarp forest, while the old nest, found in great quantities in the peat swamp forest and ecoton. The nest can be found in each habitat, with the highest frequency found in peat swamp forest (18,7 nest/km track). This high number caused by the habitats ability to provides Orangutans food resources such as leaves and tree bark troughout the year. This habitats are intact habitat unit of Orangutan, which the stand characteristic of each habitat is not the determining factor of nesting habitat preferention. The nesting habitat preferention influenced by period of Orangutan's food resources availability.