Researchers comparing foraging capabilities in great apes have discovered that bonobos use tools as extensively as chimpanzees. Various materials ranging from antlers to stones were used as levers, shovels, and even daggers. In fact, bonobos’ techniques resemble those of our early Stone Age ancestors. The findings were published in the American Journal of Physical Anthropology last month.
Bonobos (Pan paniscus) are famous for their sexual behaviors, but studies on their tool use are rare, especially in the wild. A team led by Itai Roffman from the University of Haifa wanted to compare the tool-assisted foraging capabilities of bonobos living in zoos with those living in sanctuaries. They provided the apes with natural raw materials – such as branches, antlers, and stones – and then challenged them with tasks that they hadn’t previously encountered. These involved food buried underground or inserted into the marrow cavities of long bones. Then the researchers sat back and watched as the bonobos tackled these retrieval tasks.
Short sticks, long sticks, rocks, and antlers were effectively used by the bonobos as daggers, levers, shovels, and pickax-shaped hand tools called mattocks, respectively.
With their various instruments, the bonobos successfully dug under rocks and below the ground to uncover the buried treats; they also broke the bones that contained hidden food. One bonobo successively struck a long bone with an angular hammer stone, splitting it open lengthwise – a technique previously thought to be unique to the human lineage, New Scientist reports. One bonobo even modified long branches into spears and used them as attack weapons and barriers (they may have viewed the researchers as intruders).
Bonobos in the sanctuary performed slightly better than the zoo group: Sanctuary bonobos used diverse sets of tools to perform entire sequences of actions. The dissimilarity is probably the result of differences in their cultural exposure and housing conditions.
Both the captive and semi-captive groups were then compared with wild chimpanzees (Pan troglodytes). Chimps have built a reputation for being adept tool users. Recent work with young apes, for example, found that while chimps spent time manipulating objects, bonobos were busy socializing with others. These new findings on tool-assisted extractive foraging in bonobos complement extensive data on chimp tool use and suggest that this competency is a shared trait.
Furthermore, bonobo techniques are similar to those of our Oldowan ancestors from around two million years ago. "When you give them the raw materials, they use them in correct and context-specific strategies," Roffman tells New Scientist. Modern day bonobos may help us to better understand tool use in early human ancestors.