Thursday, June 25, 2015

Potential innate difference in tool use between chimps and bonobos

Young chimpanzee. Photo credit Sabine Bresser
Koops, Furuichi and Hashimoto published a paper recently on the innate ability to use tools in chimpanzees (Pan troglodytes) and bonobos (Pan paniscus). Both species are our closest living relatives, thus providing opportunities to study the evolution of our species and determine what makes humans human. Tool use has long fascinated biological anthropologists, ever since it was first recorded by Jane Goodall at Gombe in 1960.

The authors tracked both species for three months each and recorded all instances of tool use and all instances they thought had potential for tool usage. Fourteen chimps and sixteen bonobos were studied.

Koops and her colleagues determined the available opportunities to harvest army ants and termites (insects that required tool use), nut trees and stones available below those nut trees (used to crack open the nuts) at each of the two sites. The authors determined that the opportunities for dipping for termites and/or army ants was present at both sites. Opportunities for nut cracking were available but limited.

Bonobo young spent more time with their mothers than did chimpanzees. Bonobos also spent more time in close proximity to each other in feeding contexts. Bonobos also had more individuals in close proximity and more social partners than chimpanzees did, thus bonobos had increased opportunities for social learning. Neither ape cracked nuts. Interestingly, bonobos did not fish for termites or army ants whereas chimpanzees did. Both species were more likely to manipulate objects in a resting context than in a feeding context. The most convincing evidence that there is an innate difference between these two species is that chimpanzees less than one year old were observed manipulating objects. These young animals have had few opportunities for social learning, the authors argue, thus their object manipulation is intrinsic.

I'd like to see this study replicated and expanded. Studying each species for only three months doesn't yield a very large amount of data when we're talking about behavioral studies. The more data the better, and given that chimpanzees and bonobos don't reach maturity until around age eight, it's possible study these young apes for more than a few months. I also think it'd be ideal to see this study replicated across numerous sites, incorporating different habitats. Because neither species cracked nuts, we're really only talking about using tools to fish for ants and termites. Given the diverse tool use we see in animals, I wonder if it is a bit premature to declare that chimps are inherent tool users compared to bonobos given the limits of this study. Nonetheless, Koops and her colleagues certainly made an interesting discovery, and it'll be exciting to see what they discover next, as at least one more publication on this topic appears to be in the works.

For now, chimps have a more innate propensity to use tools for army ants and termites. In the future, we very well may prove chimpanzees have more of an innate propensity for tool use than bonobos or at least a different type of innate ability to use tools.

Links of interest:
Chimps that cook
Female chimps more likely to use tools when hunting
Are bonobos more peaceful than chimps?
How human are chimps?

Literature cited:

Kathelijne Koops, Takeshi Furuichi and Chie Hashimoto. Chimpanzees and bonobos differ in intrinsic motivation for tool use. Scientific Reports, 2015 DOI: 10.1038/srep11356

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