Pongo Abelii, Sumatra

The Sumatran orangutans are much rarer than their Bornean counterparts. They are smaller and slighter (the males weigh up to 90kg/ 200 lbs, females 45kg/ 100 lbs), they have longer, lighter hair, a longer face, and cheek flanges that are covered in fine, white hairs. Compared to the Borneans, the Sumatrans eat more insects and fruit (such as figs and jackfruit) and less tree bark. They also spend even less time on the ground (possibly due to the presence of predators such as the Sumatran tiger).

The Sumatran orangutans have also been observed using tools; for example, specially-customised sticks to extract insects from bees’ nests and termite-infested branches. They also use the sticks to� withdraw the delicious seeds from the Neesia fruit whilst avoiding its nasty fibreglass-like hairs.

Unlike the solitary Borneans, Sumatran orangutans are known to form small groups to feast on mass-fruitings of fig trees. However, mature males tend to avoid contact with one another. The birth rate for the Sumatran orangutan is even lower than the Bornean: females generally have their first baby at about 15 years old.

The most significant populations are found in the Gunung Leuser ecosystem, a 26,000 km2 conservation region. The smaller Gunung Leuser National Park comprises 10,950 km2 and the Singkil Swamps Wildlife Reserve another 1,025 km2 of the total. The Gunung Leuser ecosystem is home to about 75% of the wild Sumatran orangutan population, which mostly lives outside the national park area. During the late ‘90s, it’s estimated that 1,000 orangutans per year were lost from this ecosystem due to illegal logging and conversion of the lowland forests to palm oil plantations. When the wild population may be as low as 6,000, a thousand dead orangutans in a single year represents a devastating tragedy.

There was some respite in the north-Sumatran province of Aceh due to the 30-year war for independence that occurred there, making it unsafe for people to venture into many forest regions. In 2007, Governor Yusuf Irwandi declared an official moratorium on all logging in the province, which may offer a stay of execution for Aceh’s few remaining orangutans.

Sadly, Sumatran orangutans face the same threats as in Borneo: habitat destruction due to logging, plus human encroachment, poaching and smuggling. CITES, (the Convention on International Trade in Endangered Species), a treaty drawn up in 1973 to protect threatened wildlife, places the species on Appendix I – animals critically threatened by extinction. Sumatran conservation interventions include preventing human/orangutan conflict, enforcement of wildlife and forestry laws, policing and prosecuting illegal logging and forest conversion, halting road construction, and providing connectivity between remaining forest fragments.