London, Oct 13 (IANS) Movement through a complex meshwork of small branches at tree-top levels can be quite challenging for animals wanting to forage. But scientists have found out that the bulky orangutans overcome this difficulty by their ability to move with an irregular rhythm.
Robin Crompton, professor at the University of Liverpool’s School of Biomedical Sciences, explained that these challenges were similar to the difficulties engineers encountered with London’s ‘wobbly’ Millennium Bridge.

“The problems with the Millennium Bridge were caused by a large number of people walking in sync with the slight sideways motion of the bridge. This regular pattern of movement made the swaying motion of the bridge even worse.

“We see a similar problem in the movement of animals through the canopy of tropical forests, where there are highly flexible branches,” said Crompton.

“Most animals, such as the chimpanzee, respond to these challenges by flexing their limbs to bring their body closer to the branch. Orangutans, however, are the largest arboreal mammal and so they are likely to face more severe difficulties due to weight.”

“If they move in a regular fashion, like their smaller relatives, we get a ‘wobbly bridge’ situation, whereby the movement of the branches increases,” said Crompton in a Liverpool University release.

“Orangutans have developed a unique way of coping with these problems; they move in an irregular way, which includes upright walking, four-limbed suspension from branches and tree-swaying…with increasing magnitude, until they are able to cross large gaps between trees,” said Susannah Thorpe, from University of Birmingham’s School of Biosciences.

The team studied orangutans in Sumatra, where the animal is predicted to be the first great ape to become extinct. This new research could further understanding into the way orangutans use their habitat, which could support new conservation programmes.

The research was published in Proceedings of the National Academy of Sciences.