Parkour athletes reveal orangutans’ climbing secrets
The efficiency of orangutan movement through forests has been revealed by parkour athletes wearing oxygen-measuring equipment.
Studies designed by scientists have revealed how much energy each recreated tree-to-tree manoeuvre requires.
The results could help explain how orangutans are likely to be affected as their forest environment is cut down.
The findings were presented at the Society for Experimental Biology's annual meeting in Salzburg, Austria.
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Dr Sam Coward from the University of Birmingham explained why getting human athletes to recreate the agile jumping and swinging moves of orangutans was an ideal way to find out more about the animals' lifestyles.
"We wanted to measure the energy expenditure as they moved through the trees," he told BBC Nature, "so we put a mask on [the athletes] to measure their oxygen consumption."
For one particularly precarious-looking test, the team designed a tall pole that mimicked the flexibility of a tree. The participants then used this to recreate a "tree-sway manoeuvre".
"This is something the orangutans use to cross gaps," said Dr Coward. "They sway [the tree] backwards and forwards until they're able to get across."
The team found that this method of moving from tree-to-tree used just one tenth of the energy that it cost to climb down and back up.
Dr Lewis Halsey from the University of Roehampton explained that it was crucial for the animals to have the option to move around by swaying trees because, in the wild, the animals were on an "energetic knife edge."
"They're very large animals and their food intake is quite poor, so everything they do is geared towards being energy efficient," he said.
"As their environment is affected by humans cutting down trees, they are coming across more gaps and those gaps are bigger and more expensive."
Dr Coward added that, for Sumatran orangutans, climbing down was not an option.
"They never come to the ground," he told BBC Nature. There are tigers on the forest floor, so they spend all of their time in the trees.
"If a gap becomes too large, they could find themselves isolated in one area of forest."
With their colleague Dr Susannah Thorpe, the team also hopes to translate this research into the design of zoo equipment that is a little more demanding than some of the existing climbing frames in zoo enclosures.
"Zoo animals can get fat, simply because they eat too much and don't do any exercise," said Dr Halsey.
"So it's important for zoos to devise equipment for their apes that has a little bit of flexibility built in, so it saps some of their energy."