In what could be praised as one small swing for man, one giant leap for primate science, researchers have used urban street performers to shed light on orangutan behavior.
To measure the energy efficiency of large, tree-dwelling orangutans, Lewis Halsey of the University of Roehampton turned to parkour athletes, who navigate the urban environment by leaping, swinging and bouncing their way from place to place.
"Parkour athletes are rather good versions of humans when it comes to arboreal stuff, because they're good at jumping around and swinging around, and they often take their inspiration from gibbons and orangutans."
How these heavy primates live in treetops while consuming only sparse and low-calorie fruits has long puzzled researchers. Past study of primate locomotion has focused on physics-based calculations based on size, weight and speed of animals, explained Halsey, adding that this can misrepresent energy expended. Attempts have also been made to attach devices to track animals' motion and expended energy. But, said Halsey, "Orangutans aren't very amenable to wearing equipment. They tend to take it off and rip it up."
Parkour athletes, on the other hand, were happy to navigate Halsey's obstacle course, and were similar in mass to the target species. Using the obstacle course as a proxy for orangutan environments, Halsey and his team learned how these heavy primates save energy in the treetops. [See Video of Parkour Athletes]
Jumping between compliant platforms is more efficient than jumping between hard ones that don't have any give; smaller animals (as is the case for smaller-framed urban athletes) save energy by swaying on limbs rather than jumping; and larger animals save energy by jumping rather than swaying. However, large orangutans never jump, possibly to prevent injury or because their bodies aren't equipped for jumping agility.
"We've got loads of interesting new data, but I think to really delve deeper … you need to use the subject animals," Halsey told LiveScience.
But there is still a long way to go and using orangutans continues to present challenges: Wild animals are difficult to work with and many zoos are uncomfortable with researchers interfering with animals' routines. And as forest environments of orangutans become thinner with deforestation, farther leaps and swings will be required of the animals, making study of energy efficiency more and more pertinent. Halsey and his team worry that continued environmental pressure will prevent orangutans from sustaining arboreal lifestyles on low-calorie diets.
But in the meantime, parkour provides insight into the mysterious lives of orangutans, who, like the urban athletes, will continue to sway above and around us with an easy grace that sustains their arboreal existence.
The research was presented on July 2 at the Society for Experimental Biology's meeting in Salzburg, Austria.