The Bornean orangutan, long thought to have been strictly herbivore may in fact be an omnivore, according to a report published in the latest edition of Primates journal. The report written by University of Cambridge researcher Benjamin Buckley, follows observation of a wild male Bornean orangutan eating a squirrel in a remote forest in Borneo.
Buckley is head of a research project called Tropical Peatland, a joint research project of the UK's University of Cambridge and University of Durham which has so far racked up 16,000 hours of orangutan observation time.
Herbivores are strictly plant eaters while omnivores eat both plants and meat.
Buckley says although another species of orangutan found in Borneo, the Sumatran orangutan, has been known to eat meat, this is the first time a Bornean orangutan has been seen eating any kind of meat since the Tropical Peatland project began looking into their lives in 2003.
Buckley says that just before researchers saw the orangutan devour a squirrel "he was acting aggressively, throwing branches and shaking trees.” When he calmed down to eat, he turned his back on the research team each time observers tried to see what he was eating.
"After a short while I managed to find a spot to watch him clearly," says Buckley. "I saw that he had a squirrel in his hand, which he was tugging at with his teeth, and I could hear crunching noises as he chewed."
Buckley says "The entrails of the squirrel were dropped but every other part of the carcass was chewed and swallowed, including bones, skin, fur and tail."
The researcher say the squirrel most probably had not been hunted as "it is unlikely that a large adult male orangutan would be capable of chasing and catching a creature as agile as a squirrel," adding that the orangutan may have "scavenged" a dead squirrel "opportunistically".
What interested Buckley the most was the fact the orangutan ate the squirrel despite there being plenty of fruit to eat in the area. The other species of orangutan which live on the island of Sumatra, have been observed eating meat on five occasions since 1999, but only when fruit was scarce.
Durham University's Adriano Lameira who has seen the Sumatran orangutans eating meat, says humans and orangutans share a common ancestor which lived an estimated 12 million years ago.
"This study puts us a step further in understanding what may have been the 'ingredients' of the first food cultures to emerge in our lineage," says Lameira. "Such individual food preference can be passed on through generations, or spread horizontally across populations, giving raise to diet cultures."