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

Female chimps are more likely than males to use tools when hunting

The hunted (a galago). Credit: flickr user Robertsphotos1

Jill Pruetz and colleagues recently published a great study about sex differences in tool use in chimpanzees (Pan troglodytes verus). Pruetz works at Fongoli in southeastern Senegal. Fongoli is different than most chimpanzee study sites because it's actually a woodland-savannah. Most chimpanzee study sites, such as Gombe, are characterized by deciduous, woodland, or evergreen forests. Anyways, chimpanzees at Fongoli hunt bushbabies or galgoes (Galago senegalensis ) using sticks they've essentially sharpened into spears. The chimps will break off a branch and frequently use their teeth to sharpen the end of the stick. They're taking an object found in their environment and modifying it to suit their needs. This is the only site where chimpanzees have been observed hunting using tools. Recently and after years of data collection, Pruetz and colleagues discovered some interesting differences in hunting between the two sexes.

Over the course of the study, ninety-nine instances of chimpanzee hunting were recorded, including episodes during which tools were used. Both male and female chimpanzees hunt Galago more than any other vertebrate at Fongoli. After observing and documenting episodes of chimpanzees hunting with the use of tools, females were significantly more likely to use a tool than were males. Pruetz and colleagues (2015) report 170 instances of females using tools compared to 130 instances of males using them when hunting.

Uh oh fellas, does this mean female chimps are smarter than males? No, it doesn't. Let's not jump to any conclusions here.

Pan troglodytes. Photo credit: William Warby

There could be multiple reasons for females hunting with tools more than males. Perhaps females are smarter than males in this population and use tools to aid them when hunting. On the other hand, perhaps females use tools because they are weaker physically than male chimps, thus tool use makes hunting easier for them and compensates for this difference in strength. Both are possible answers and there are likely others. The study showed this difference in males and females is significant, thus it is not random that Pruetz and colleagues observed more females using tools when hunting than males. Pruetz and colleagues hypothesize that males may use tools less often when hunting Galago than females because males usually hunt larger prey, and thus when they flush out Galago individuals, it is opportunistic: they are not using tools to hunt baboons or other large prey they're targeting.

This isn't the only difference between the sexes when it comes to chimpanzee hunting. Males are known to hunt more than females (Fahy et al., 2013; Stanford, 1999). At Fongoli, Pruetz and colleagues also found while Galago made up 75% of females' prey, it accounted for only 47% of males'. Only male chimpanzees at Fongoli hunt patas monkeys (Erythrocebus patas). Successful hunters were more likely to be male than female. However, when both sexes used tools to hunt Galago, there was no difference in success rate between males and females.

As Pruetz and colleagues discuss in this paper, their study has implications for human evolution. Tools likely played a part in how our early human ancestors hunted, thus studying chimpanzees allows us to better understand what hunting may have looked like in early humans.

Food for thought: Can you think of any reasons why females use tools to hunt more frequently than males do?
Why might chimps use tools to hunt at Fongoli and not elsewhere?

Links of potential interest:
Video of Pruetz discussing chimps hunting bushbabies
Nat Geo article on Fongoli chimps
Tool Use, Hunting, and Other Discoveries

Sources:
J. D. Pruetz , P. Bertolani , K. Boyer Ontl , S. Lindshield , M. Shelley , E. G. Wessling. New evidence on the tool-assisted hunting exhibited by chimpanzees (Pan troglodytes verus) in a savannah habitat at Fongoli, Sénégal. Royal Society Open Science, 15 April 2015
Fahy, G.E., Richards, M., Riedal, J., Hublin, J., Boesch, C. 2013. Stable isotope evidence of meat eating and hunting specialization in adult male chimpanzees. Proc. Natl Acad. Sci. USA 110, 5829-5833 
Stanford, C.B. 1999. The hunting apes:meat eating and the origins of human behavior. Princeton, NJ: Princeton University Press.

How human are chimps? The differences and similarities between chimpanzees and humans.

The state of New York recently ruled that chimpanzees are not entitled to the same privileges and rights as humans. Chimpanzees have long given humans plenty to think about when it comes to defining what exactly is human. Jane Goodall, when she observed chimpanzees using tools in the wild stated, "Now we must redefine tool, redefine Man, or accept chimpanzees as humans." I decided to look at some of the ways chimps are just like us and some of the ways they're not at all like humans.

Young chimpanzee. Photo credit Sabine Bresser

Like humans:

1. Chimps taken from their mother at a young age suffer long-lasting behavioral consequences. Specifically, chimps raised by humans rather than other chimps groom each other less frequently than chimps raised by their chimpanzee mothers, and they also engage in sexual behaviors less frequently. Read the study done by Freeman and Ross at the Lincoln Park Zoo here. Looks like each species should probably raise its own young.

2. Chimps can cooperate and do so spontaneously. In a study where chimpanzees were given access to a task in a larger outdoor area, as opposed to a small, controlled area where most testing typically occurs, chimpanzees had the choice to use the apparatus and try the task or avoid it entirely. Surprise! Chimpanzees chose to use the apparatus, which required cooperation and choosing a partner chimpanzee to achieve the task, meaning chimps don't just work together when there's nothing better to do. These chimps sought cooperation out. Check out the article by Suchak and others here.

3. Chimps display different cultures, as shown by separate populations of chimpanzees using tools in different ways despite seemingly the same ecological conditions. A 2010 study examined how two populations obtain honey (a real treat for a chimpanzee) and found one population using sticks while another used wedges of leaves to soak up the delicious and highly coveted food item.

Unlike humans:

Photo credit Sergio Morchon

1. Chimpanzees may be able to communicate, but they have yet to display a mastering of complex language and grammar. While yes, chimps and other apes have a grasp of sign language and some even use computers and symbols to communicate with humans, are they capable of knowing the difference between sentences such as, "I bit the dog" and "The dog bit me?" The answer appears to be no. For a great film that I highly recommend, watch Project Nim. It's thought-provoking, heartbreaking, informative, and definitely worth a watch if you're interested in language or even more broadly interested in chimps.

2. Chimpanzees don't teach their young. Now, this might be a somewhat controversial claim since teaching in animals is hard to study (how do you determine if one it is one individual's intent to share knowledge with another?). Chimps certainly learn by watching other chimps and new behaviors are socially transmitted, but does one chimpanzee purposefully and knowingly teach another? Even if you disagree with me, you must admit that humans take teaching to a new level. With our creation of schools and our ability to guide and help others in a hands-on way, we take teaching to a level definitely not seen in chimps.

3. Finally, chimpanzees are not nearly as adaptive as humans when it comes to geography. Homo sapiens, or humans as we know and love ourselves today, weren't even the first to leave Africa and travel to other continents. Our earlier humans ancestors did that first, but the fact remains, humans love to travel. We have blogs dedicated to traveling, the desire to know what's just over that mountain or on the other side of the lake. We seemingly need to go everywhere and we're on every continent if you include the research done in Antarctica. We've adapted to all of these different climates through tools and clothing and behavioral adaptations. I don't think anyone can argue chimps have caught the travel bug quite like humans have.

Food for thought: Does learning these facts about chimps change the way you view what it means to be human? What is the most important difference between chimps and humans? What is the most important similarity?