Their long arms which make them well suited to their treetop lifestyle.
They measure between 115-137cm tall and weigh between 40-90kg.
Fruit and leaves make up around 60% of their diet. They eat a lot of food and sometimes spend whole days gorging
They spend most of their time living in the trees in the lowlands of Borneo.
There are approximately 55,000 Bornean orang-utans in the wild.
Habitat loss, drought and fire.
Like us, orang-utans will often use tools to help them and have been spotted using leafy tree branches to shelter them from the rain like an umbrella.
Listen to a Bornean orang-utan.
Watch an orang-utan in a video from our friends at ARKive