Nest characteristics and populations of Tapanuli Orangutans in the conflict areas, Batangtoru Landscape, North Sumatra, Indonesia

Abstract

Abstract. Kuswanda W, Harahap RH, Alikodra JS, Sibarani R. 2020. Nest characteristics and populations of Tapanuli orangutans in Batangtoru Landscape, South Tapanuli District, Indonesia. Biodiversitas 21: 3398-3406. Tapanuli orangutan (Pongo tapanuliensis) has been threatened to extinction due to conflicts with humans. Information on the orangutan characteristics in conflict areas at the Batangtoru Landscape is needed. Our research aimed to analyze the characteristics of nests, nest trees, and estimation of orangutan populations in conservation forests and buffer zones to develop conflict mitigation strategies in the Batangtoru Landscape, South Tapanuli District. A line transect method was used to count orangutan nests on 49 transects, starting from June 2019 to January 2020. Data were analyzed with descriptive statistics, frequency tables, Spearman correlation (rho), and the equation by (van Schaick et al. 1995). Tapanuli orangutans make nests at the height of 14.01 meters (90% CI = 13.37-14.67 meters), and most use the main stem as nest support. Tree nests of 35 species (17 families) were identified, with the highest frequency in (Durio zibethinus Murray), especially in the buffer zone. Correlation between nest tree diameter, tree height, and canopy area was significant (p <0.01, n = 83). The estimated orangutan populations in conflict areas were 155 individuals (95% CI = 121-187), and the highest was found in Dolok Sibualbuali Nature Reserve buffer zones. Mitigation strategy of human-orangutan conflict that needs to be realized is the non-cash compensation guaranteeing the community does not disturb orangutans on their land. The compensation forms can be the provision of seedlings and fertilizer for plants, agricultural machinery, knowledge to land management, and orangutan ecotourism development. Nest and feed trees enrichment can be carried out in production forests bordering with conservation area.

Population Status of Tapanuli Orangutan (Pongo tapanuliensis) within the Renewable Energy Development and its Management Implications

“…The distribution of Tapanuli orangutan was focused in undisturbed forest (Wich et al, 2012), and other populations could be found in the disturbed forest (Nasution et al, 2020;Kuswanda et al, 2020). Aligned with those findings, Rahman et al (2019) calculated the suitability habitat for Tapanuli orangutan, which protected area was potentially suitable for orangutans i.e.…”

“…As the distribution of Tapanuli orangutan was separated into two different and more significant populations i.e. west and east blocks (Wich et al, 2019), and the population within the east block was scattered into some small populations (Nasution et al, 2020;Kuswanda et al, 2020). The local government has initiated the creation of corridors to connect the orangutan populations known as Sibual-buali corridor and Sipirok corridor to connect the west and east population, and a corridor to connect Sibual-buali and Sipirok populations.…”

“…Although, the implementation might be challenged, the collaboration could be conducted with local communities and government. The previous findings on orangutan distribution outside the protected area shall be considered (Nasution et al, 2020;Kuswanda et al, 2020).…”

Characteristics of the Tapanuli Orangutan Habitat in the Conflict Area of Batang Toru Landscape, North Sumatra, Indonesia

“…The difference in the vegetation compositions between blocks was thought to have influenced the lives and populations of orangutans. Orangutan populations in the Eastern Block was lower than that in the West Block (Kuswanda et al, 2020;Ministry of Environment and Forestry, 2019). Orangutans would move to habitats that provided forage plants, especially fruits, even if they were available in the community's cultivated lands (Hockings and Humle, 2010).…”

“…The research was focused on South Tapanuli because the conversion rate of forest cover into cultivated land is fast, leading to frequent human-orangutan conflicts in Tapanuli (Kuswanda, 2014;Haryanto et al, 2019). Kuswanda et al (2020) stated that the conflict area in South Tapanuli District was estimated at 29,192 ha with an orangutan population of 155 individuals. This area includes 20 villages in four sub-districts with a population of around 17,347 people.…”