King of the swingers: how orang-utans are like free-runners The scientists found that the ways in which the athletes swung across gaps, used walls to gain height and moved over obstacles using all four limbs were all similar to orang-utan movements. "Free runners try to move as efficiently and as smoothly as possible through their environment," said Dr Susannah Thorpe, a senior lecturer in biomechanics at the University of Birmingham. This is exactly what orang-utans are trying to do when they are moving around in the forest. It is a complex environment with gaps in the canopy, branches and some open spaces, so they have to move through this using as little energy as possible to get between food sources. When moving along a beam that mimics a branch, the free-runners use all four limbs to support themselves and we see this in orang-utans in the wild. The way they climb is also very similar. Dr Thorpe said: "It is difficult to study how much energy primates use in the wild, so the free-runners can give us a more direct way of assessing this. Some of the free-runners move quite slowly through the course, while others will try to move faster. The strategies they use are quite diverse and we see this among orang-utans. Orang-utans, standing only four feet tall but with a seven-foot arm span, can weigh up to 180lbs. They share 97 per cent of their genes with humans. The original "king of the swingers," the species spends most of its life in the treetops of rainforests of Indonesia and Malaysia, eating mainly fruit. Dr Lewis Halsey, a senior lecturer in the department of life sciences at the University of Roehampton, said: "We are focusing on three key orang-utan locomotor behaviours - tree swaying, because of its role in reducing locomotion cost, vertical climbing. since this requires the animal to oppose gravity, and leaping, since while probably energetically efficient, orang-utans only leap in extremes."