Some 56 years after Jane Goodall began long-term research on wild chimpanzees at Gombe, Tanzania, primatologists are still uncovering fascinating new facts about these closest living relatives of ours.
In a paper published in Scientific Reports last week, "Tool transfers are a form of teaching among chimpanzees," Stephanie Musgrave, an anthropology graduate student at Washington University in St. Louis and her co-authors David Morgan, Elizabeth Lonsdorf, Roger Mundry and Crickette Sanz document — for the first time, they say — that wild chimpanzee behavior meets the scientific criteria for teaching.
That's big news.
We already knew a lot about chimpanzees and tool behavior, of course. These apes acquire food like termites, ants, nuts and honey by making and using tools in different ways at different locations. Youngsters pay close attention to what their elders do, and make mistakes as they refine their techniques; they are cultural learners, acquiring the habits of their own specific communities.
Attunement to adults by infants and juveniles is one thing, but there's been a paucity of evidence of outright teaching in wild chimpanzees. A paper published in 1991 by Christophe Boesch has become famous for its exceedingly rare report of two cases of active teaching: mothers showing nut-cracking techniques to their offspring.
But in reporting their research on teaching carried out at Goualougo Triangle within the Nouabale-Ndoki National Park in the Republic of Congo, Musgrave et al. do something unprecedented. They derive their conclusions from archived, remote video data collected over a 7.5-year period from passive infrared cameras (camera traps) set up at termite nests. Chimpanzee adults were "caught in the act" of transferring brush-tipped termite-fishing probes they had fashioned out of herb stems to apprentice learners who were eager for a protein snack.
This, the authors argue, is teaching, because all three things required in order to claim teaching in non-human animals are present.
First, the tool transfers happened in the presence of a learner. Of 57 transfers of fishing probes with enough information to analyze (from a larger set of 96 caught on video), all but one occurred between an adult female and her offspring.
Second, the transfers came at a cost to the donor. "Donors incurred costs," Musgrave et al. write, "in the form of reduced time spent termite gathering, fewer fishing probe insertions, and reduced termite consumption."
Third, the transfers improved the learner's performance. From the paper: "Tool recipients increased their time spent termite gathering, and showed higher rates of fishing probe insertions and feeding events following transfers."
So these chimpanzees really do teach! And, as I say, that really is news.
Earlier this week, I contacted Musgrave — who was an undergraduate student of mine some years back in the anthropology department of the College of William and Mary — and we corresponded about the paper by email. Musgrave told me:
"Drs. Sanz and Morgan carried out the fieldwork, including installation and monitoring of the camera traps in the forest, and I scored the video footage. We have observed many instances of tool use and transfers during our daily follows of chimpanzees in the forest, but the remote cameras have provided a major advantage in allowing us to continuously monitor more than 30 tool sites across the entire community range."
When I commented that I thought the data on cost-to-chimpanzee donors was especially exciting, Musgrave noted that sometimes mothers find a way to buffer those costs:
"Mothers sometimes arrived at the termite nests carrying multiple tools, or split their fishing probes lengthwise to create two functional tools. Both of these strategies enable the mother to provide her offspring with a usable tool without comprising her own ability to forage."
That's a smart strategy, and it's shown beautifully in this video clip from the Goualougo research:
Camera traps, while not new in animal-behavior field research, have great potential to revolutionize our understanding of animal intelligence, and maybe even emotion, when they're used as part of rigorous analytical methodology. As anthropologist and study co-author Crickette Sanz commented in a press release from Washington University, they also allow scientists to reduce pressures on the study animals:
"We have observed a generation of chimpanzee kids learn how to use these tool sets, without having to spend a decade habituating them to human presence or risk exposing them to anthropogenic diseases."
(By the way, inexpensive versions of these camera traps can be installed in our own backyards — just for fun. We recently did this here in Virginia, and I'm now treated some weeks to a parade of images ranging from a coyotes to raccoons who feel at home here with us. No termite-fishing chimpanzees, understandably.)
In sum, the research by Musgrave et al. shows that at least sometimes in some locations, chimpanzees use their capacities for understanding subjectivity and perspective — a topic Alva wrote about here last week — to teach those with less knowledge. That means, of course, each generation doesn't have to invent tool-making and tool-using practices anew, which would be extremely clumsy and costly.
Chimpanzees clearly don't rely on teaching anywhere near as much as we humans do in societies around the world, and that remains a fascinating evolutionary puzzle in itself.
Barbara J. King is an anthropology professor emerita at the College of William and Mary. She often writes about the cognition, emotion and welfare of animals, and about biological anthropology, human evolution and gender issues. Barbara's most recent book on animals is titled How Animals Grieve, and her forthcoming book is Personalities on the Plate: The Lives and Minds of Animals We Eat. You can keep up with what she is thinking on Twitter: @bjkingape