Camp Leakey, at the top of the river, is the historic site — the research station founded by Biruté Galdikas in 1971 and still the most famous orangutan study area in the world. Its feeding platform draws semi-wild orangutans including individuals whose lineages have been followed for decades.

Pondok Tanggui and Tanjung Harapan, lower down the river, are the other feeding stations, each with its own resident animals and generally fewer visitors than Camp Leakey.

The riverbanks from the boat are where the rest of the wildlife is. Proboscis monkeys gather in riverside trees to sleep in the late afternoon, long-tailed macaques work the margins, hornbills cross overhead, and false gharial and crocodiles lie on the mud.

The night on the river adds fireflies in the trees along the bank in numbers that can light a whole tree, plus nightjars and the calls of the swamp forest.

The drier months from June to September make walking easier and are the most popular; the wetter months are quieter and the forest is greener.

Practicalities

Pangkalan Bun is the gateway, reached by flight from Jakarta or Semarang, with the boats leaving from Kumai nearby. Trips are booked as packages including the boat, crew, cook, guide and park permits.

A word on the ethics: these are rehabilitated and provisioned animals, not an untouched wild population, and the feeding stations exist for animals that could not otherwise survive. Keep the required distance — orangutans are susceptible to human respiratory infections — and never let a guide encourage contact.