Here, in the mountainous forests of Batang Toru, is where they had always seen and heard the world's rarest ape, the Tapanuli orangutans. Their absence has fuelled speculation as to whether the great apes were swept away by floods and landslides. Fewer than 800 Tapanuli orangutans remain and any loss would have a serious impact on the species, conservationists say. He previously worked in the conservation of the Tapanuli orangutans. Conservationists working in the region believe it is of the Tapanuli orangutan, a species that was only discovered in 2017.