Tapanuli Orangutan Population Estimated at 716 Individuals: Is All Well?

The population of the critically endangered Tapanuli orangutan (Pongo tapanuliensis) in the wild is currently estimated at around 716 individuals. This estimate is the result of a survey conducted throughout the Batang Toru ecosystem in North Sumatra from 2021 to 2023. The findings were published in the journal Global Ecology and Conservation on June 20, 2026, in a paper titled “Population Status of Sumatran and Tapanuli Orangutans: A Comprehensive Assessment 2021–2023.” The survey, led by Adhi N. Hadi and Julius P. Siregar along with over a dozen researchers from Indonesia, the UK, and Germany, utilized 208 nest transect lines spanning 198 kilometers within the habitat of both Sumatran and Tapanuli orangutans. In the Batang Toru area, researchers surveyed 57 kilometers of transects and recorded 330 nests. These data were analyzed using distance sampling and spatial modeling to estimate the population. "The results indicate that the Tapanuli orangutan population is estimated at 716 individuals, all living within the 102,185-hectare Batang Toru ecosystem. A total of 514 individuals (72 percent) are in West Batang Toru, 159 individuals in East Batang Toru, and 43 individuals in the Sitandiang–Sibualbuali area, with an average density of 0.70 individuals per square kilometer," wrote Adhi and colleagues. Compared to an earlier estimate from 2011 of around 767 individuals, this figure suggests a decline. "However, comparisons must be made cautiously as the methods and coverage of previous surveys differed," the researchers noted. The research also emphasizes that the Tapanuli orangutan has a very small demographic buffer, meaning even minor increases in mortality can threaten the population's survival. "Orangutan density is highly dependent on intact forests, while human pressures such as encroachment, conflict, hunting, and habitat loss remain the primary threats." The study explains that approximately 78.6 percent of the population resides in protected forest areas, with only 9.5 percent in conservation areas. The remainder are found in production forests and other land uses.