Orangutans employ unique strategies to control branch flexibility.

Susannah Thorpe, R Holder, RH Crompton

Research output: Contribution to journalArticle

46 Citations (Scopus)


Orangutans are the largest habitually arboreal mammal. For them, as for all arboreal mammals, access to the abundant fruits and narrowest gaps found among the thin peripheral branches of tree crowns poses considerable safety risks and energetic demands. Most arboreal primates use flexed-limb postures to minimize problems caused by branch compliance and instability. Here, we show that Sumatran orangutans employ unique locomotor strategies to control compliance and allow access to the terminal branch niche for feeding and gap crossing. We calculated a "stiffness score," which is a measure of the flexibility of the supports on which orangutans moved. We found that certain locomotor behaviors clearly are associated with the most compliant supports; these behaviors appear to lack regular limb sequences, which serves to avoid the risk of resonance in branch sway caused by high-frequency, patterned gait. Balance and increased stability are achieved through long contact times between multiple limbs and supports and a combination of pronograde (horizontal) and orthograde (vertical) body postures, used both above branches and in suspension underneath them. Overall, adult females seem to be the most conservative in their travel, selecting more solid and secure supports than males and adolescents. These results have implications for understanding locomotor diversity in fossil and extant apes and for orangutan conservation and reintroduction programs.
Original languageEnglish
Pages (from-to)12646-51
Number of pages6
JournalNational Academy of Sciences. Proceedings
Issue number31
Publication statusPublished - 4 Aug 2009


Dive into the research topics of 'Orangutans employ unique strategies to control branch flexibility.'. Together they form a unique fingerprint.

Cite this