All three recognized orangutan species — Bornean, Sumatran, and the recently described Tapanuli — are Critically Endangered, with palm oil-driven deforestation as the best-documented cause of their collapse.
Three orangutan species are currently recognized: Bornean (Pongo pygmaeus), Sumatran (Pongo abelii), and Tapanuli (Pongo tapanuliensis) — the latter formally described as a distinct species only in 2017, based on genetic, morphological, and behavioral differences. All three are listed as Critically Endangered by the IUCN, making orangutans the only great apes with every recognized species at the highest non-extinct threat level.
The Tapanuli orangutan, confined to a single forest area in North Sumatra, is estimated at fewer than 800 individuals — the smallest population of any great ape species — and is considered at risk from a single road or mining project that could fragment its remaining habitat.
Source: Nater et al., Current Biology, 2017; IUCN Red List assessmentOrangutans are the largest arboreal mammals, spending the vast majority of their time in the forest canopy, and have one of the slowest reproductive rates of any mammal — females typically give birth only once every 6–9 years, the longest inter-birth interval of any land mammal. This slow reproduction means orangutan populations recover extremely slowly even after threats are reduced.
Roundtable on Sustainable Palm Oil (RSPO) certification, protected-area expansion, and orangutan rehabilitation/release programs are the primary tools in use, alongside legal challenges to specific infrastructure projects within critical habitat, such as the Batang Toru hydroelectric dam in Tapanuli orangutan range.
Population estimates rely on nest-count surveys extrapolated across large forest areas using density models, which carry meaningful statistical uncertainty. The long-term effectiveness of palm oil sustainability certification in actually halting further habitat conversion remains debated among conservation researchers.