Bonobo Apes Capable of Making Spears - and Using Them

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A bonobo holding stone tools.
A bonobo holding stone tools.Credit: Itai Roffman, courtesy

Making tools to attack one’s fellow ape had been thought to be the prerogative of man. Now, though, a University of Haifa study has found that bonobos – formerly thought to be sex-crazed chimpanzee analogs brimming with bonhomie – are capable of toolmaking with aggression in mind.

Or, at least, one is, reports Itai Roffman in the American Journal of Physical Anthropology. He found himself being targeted by a dominant female bonobo who shaped a spear out of a branch using her teeth. Every time he tried to approach her enclosure, she tried to stab him.

Females, not males, are dominant in bonobo society, and they have proven capable of complex planning in order to get food.

“I believe that the current study will break down our cultural hang-up as humans concerning the inherent capabilities and potential of bonobos and chimpanzees,” stated Roffman.

Ancient hominin man not only made tools to eat and slaughter, he made enough to completely alter a Saharan landscape. Moving onto animals, not a few birds and mammals have been observed making and using implements.

Chimpanzees, a first cousin of the bonobo, have been seen in nature making tools – cleaning twigs to fish ants out of anthills and bees from hives, for example. They have also been observed breaking nuts with rocks serving as hammer and anvil, and even manipulating branches into spears for use in the hunting of monkeys, which they like to eat.

Chimpanzees have also been associated with premeditated murder, which had previously also been thought to be a prerogative of man.

The same murder study found that bonobos were relatively pacific: just a single suspected killing was observed during 92 combined years of observation at four different sites, compared with 152 murders by chimps during 426 combined years of observation, in 18 different chimp communities.

The amiable bonobos, aside from using most of their time to have casual sex, had been thought simpler and more primitive than chimps. Roffman had previously shown that two bonobos (who grew up in a humanized environment) could use tools to obtain inaccessible food. Now, observing eight bonobos at Wuppertal Zoo, Germany, and seven at the Bonobo Hope sanctuary in Iowa, he showed them capable of performing a complex list of actions in order to obtain food – a level of capability that apes were not expected to achieve.

The assemblage of items for potential use as tools: stones, sticks, branches and antlers.Credit: Itai Roffman, courtesy

Not all bonobos are created alike

For some reason, the apes at the Iowan sanctuary were much quicker on the uptake than the ones in the zoo. The sanctuary apes took mere days to work out how to reach food buried deep and covered by stones, or hidden in the marrow space of large bones, or concealed inside thin concrete capsules.

The potential tools available to them were stones, green branches and deer antlers.

The bonobos worked out that they had to start by removing the stone layers, which they did by hand and using sticks and antlers. Then they dug into the earth using short branches, then used bigger branches as shovels to widen and deepen the holes – employing the antlers again as awls, mattocks or rakes. Finally, they extracted the food using a long branch as a pole and lever. They also used stones and antlers as hammers to break the bones or concrete capsules to get to the food inside.

The zoo bonobos also got there eventually, but it took them a month and their performance was not comparable, Roffman said.

The way the bonobos handled the tools and bones seem analogous to archaeological findings from prehistoric pre-humans. Horn cores and bones found in South African caves bear markings indicating that they were used to dig. Neanderthals and Cro-Magnons both broke long bones (to get at the marrow), just like the bonobos.

“The bonobos essentially showed that once they have the motivation to do so, they have analogous capabilities to those of archaic pre-humans, which is logical as chimpanzees and bonobos are our genetic sister species,” Roffman noted (our degree of genetic sharing: about 99 percent).

So why haven’t our cousins the bonobos evinced such behaviors before? Evidently, because they didn’t have to. They live well, these guys. Once conditions of food stress were simulated, forcing them to strain to obtain food, they proved up to the job.

The zoo crowd did achieve one thing that their sanctuary luminaries did not. Or rather, one particular bonobo achieved something extraordinary: the dominant female, Eja, shaped a spear from a long stick, using her teeth to hone the thing – in order to attack Roffman.

Chimpanzees, which as we said are not as nice as bonobos, have been known to use spears to hunt monkeys hiding in holes, but not in a social context of attack and defense. Roffman suggests Eja felt threatened by him because he was a trespasser. “This shows how even a species that is considered peaceful and loving becomes aggressive and suspicious in social contexts of incarceration and mistrust in humans,” he said.

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