Orangutan Kalimantan survey in Sebangau National Park—Bukit Baka Bukit Raya National Park Corridor
The population of orangutan in Sebangau National Park according to WWF-Indonesia are 5,826 individuals (WWF Central Kalimantan, 2015). Based on that number, the population is the largest within conservation areas in Central Kalimantan. Although based on Population and Habitat Viability Assessment Orangutan (2016) using Vortex Analysis, this number will last for next 100 years, there will be an effort to connect the orangutan habitat to other habitats so that the survival of this population is maintained.
Efforts that can be made are connecting the habitat of the Sebangau National Park, which is a Peat Swamp Forest type, with Bukit Baka-Bukit Raya National Park (BBBR National Park), a highland forest. Among the two conservation areas, there are approximately ± 115,000 ha of forest area with forest types of Peat Swamp Forest, Heath Forest, and Lowland Forest. This area is also included in three Forest Management Units (Kesatuan Pengelolaan Hutan/KPH) unit III, XV and XVII.
Based on the Regulation of Directorate General of KSDAE No. P.8/2016 concerning guidelines for determining the wildlife corridor as an essential ecosystem, determining an area as animal habitats or wildlife corridors requires a variety of preliminary information, both from the ecological and socio-economic aspects of the community in the area that considered as potential corridor.
Therefore, a survey to determine the diversity of species and distribution of fauna in forest area of Sebangau-TNBBBR National Park Corridor were completed between December 2017—June 2018. The survey was also conducted to determine the structure and composition of the vegetation of endemic plants in the corridor. It involved teams from WWF-Indonesia, mammal experts, bird experts, vegetation experts, flying insect experts, MAPALA SYLVA, and communities around the area.
One component that was conducted in the survey was the survey of Orangutan Kalimantan, including determining nest positions and nest classes.
Determining Nest Position and Nest Grade
Data retrieval is done by tracing the transects that have been done, using distance program and citing several criteria to determine the population density of orangutans, ficus, and fruit trail. These criteria including distance of the nest perpendicular to the observation path (ppd), nest position, nest grade, etc. Nest position is divided into 5, namely position 1, position 2, position 3, position 4, and position 0.
Furthermore, orangutan nest are divided into 4 grades, namely grade A, B, C, and D. Grade A nests are new nests and are characterized by greener leaves, grade B nests are characterized by the presence of withered and yellowing leaves, grade C nests are old nests characterized by dry and brown leaves yet the nest still solid, and the grade D nests are the obscured, characterized by few twigs and the shape of the nest has worn out.
This survey has done on 22 transects. The presence of orangutans (Pongo pygmaeus) can be detected in 21 transects through indirect encounters, namely nests and feeding and direct encounters when the process of travel to the location of the target transect. According to IUCN (2018), orangutans (Pongo pygmaeus wurmbii) enter into critical species (Critically endangered). Orangutans are in Appendix 1.
Nest Density and Orangutan Population
The nest data analysed are the nest in the observation transect. According to results of the survey with a total length of 21,740 meters transects, the orangutan nest density in the Sebangau-TNBBBR TN corridor is 228 nests / km². The density of orangutans per square kilometer is 0.59 individuals (the proportion of nest-making orangutans = 0.89; the number of nests made by an average orangutan per day = 1.16; the length of nest time from the beginning is made until weathered per day = 365). During the observation, orangutans were also found directly.
The estimated number of orangutan populations in the Sebangau-TNBBBR National Park corridor after being calculated with land cover that is still a forest is 700 individuals from 1,168.2 km² of forest cover area. This result, according to orangutan experts, is quite good, so that the survival of the next 100 years will still survive.
During the observation there were 177 orangutan nests in the observation transect, with the number of nests in class 1 with 9 nests, class 2 nests with 10 nests, grade 3 nests with 63 nests, and class 4 nests with 95 nests.
In addition to orangutans, during a survey conducted in forest areas around 3 regencies – namely Katingan, Palangka Raya, and Gunung Mas, Central Kalimantan, there are also 253 plant species, 106 bird species, 17 species of mammals, 23 species of dragonflies, and 21 type of butterfly found. There are 80 species of plants which are protected, threatened and endemic to the island of Borneo. This area is easily accessible in various directions so that the threat to this area is even greater.
Based on the results, the team provided several recommendations for the management of the Sebangau-TN BBBR Corridor. The first is sustainable use without ignoring the values of the protection, preservation and value of local cultural identity. Intensive security is needed for the area and forest because it stores a variety of typical plant species of Borneo which are very diverse and many of them are protected, threatened, and endemic to the island of Borneo. The need for strict law enforcement against violations found around the Sebangau National Park TN-BBBR Forest Corridor. In addition, it is necessary to propose this area as an Essential Ecosystem Area so that its sustainability will be maintained.