Compared with the Bornean orangutan, the Sumatran orangutan tends to be morefrugivorous and especially insectivorous. Preferred fruits include figs and jackfruits. It will also eat bird eggs and small vertebrates.Sumatran orangutans spend far less time feeding on the inner bark of trees.
Wild Sumatran orangutans in the Suaq Balimbing swamp have been observed using tools. An orangutan will break off a tree branch that is about a foot long, snap off the twigs and fray one end. It then will use the stick to dig in tree holes for termites. They will also use the stick to poke a bee's nest wall, move it around and catch the honey. In addition, orangutans use tools to eat fruit. When the fruit of the Neesia tree ripens, its hard, ridged husk softens until it falls open. Inside are seeds that the orangutans enjoy eating, but they are surrounded by fiberglass-like hairs that are painful if eaten. A Neesia-eating orangutan will select a five-inch stick, strip off its bark, and then carefully collect the hairs with it. Once the fruit is safe, the ape will eat the seeds using the stick or its fingers. Although similar swamps can be found in Borneo, wild Bornean orangutans have not been seen using these types of tools.
NHNZ filmed the Sumatran orangutan for its show Wild Asia: In the Realm of the Red Ape; it showed one of them using a simple tool, a twig, to pry food from difficult places. There is also a sequence of an animal using a large leaf as an umbrella in a tropical rainstorm.
The Sumatran orangutan is also more arboreal than its Bornean cousin; this could be because of the presence of large predators like the Sumatran Tiger. It moves through the trees by quadrumanous locomotion and semibrachiation.
The Sumatran orangutan is more social than its Bornean counterpart; groups gather to feed on the mass amounts of fruit on fig trees. However, adult males generally avoid contact with other adult males. Subadult males will try to mate with any female, though they probably mostly fail, since mature females are easily capable of fending them off. Mature females prefer to mate with mature males. Male Sumatran orangutans sometimes have a delay of many years in the development of secondary sexual characteristics, such as cheek flanges and muscle mass.
The average interbirth rates for the Sumatran orangutan is 9.3 years, the longest reported among the great apes, including the Bornean orangutan. Infant orangutans will stay close to their mothers for up to three years. Even after that, the young will still associate with their mothers. Both orangutan species are likely to live several decades; estimated longevity is more than 50 years. The average of the first reproduction of P. abelii is around 15.4 years old. There is no indication of menopause.
Nonja, thought to be the world's oldest in captivity or the wild at the time of her death, died at the Miami MetroZoo at the age of 55.
There are many threats that the Sumatran Orangutans are facing that are drivng them to extinction, read about them here - Sumatran Orangutan facing extinction