A bad day’s fishing is better than a good day’s work for chimps too

When we discovered that chimpanzees (Pan troglodytes) ‘fish’ for termites we also learned that humans are not unique in our use of tools.

But until now, research has overlooked the importance of how termite ecology might shape their predator-prey interaction with chimpanzees.

Now, scientists have sought to understand how the ecology of mound building termites (Macrotermes subhyalinus) effects chimps’ abilities to fish for them, in the Issa Valley in Tansania. The findings are published in a new study in Frontiers in Ecology and Evolution.

The researchers copied chimp behaviour to see whether the seasons affect when its best to forage for termites. They found that termites are most available early in the wet season and, although other foods are abundant at that time, chimpanzees choose to fish then.  

So, the chimpanzees use tools to fish for termites because they can, not because they need to.

Chimpanzees fish for termites via flight holes in termite mounds, from which the insects emerge and disperse to start a new colony elsewhere. In some places chimps fish all year, but in others the behaviour is only seasonal.

Tools vary between chimpanzee populations. It’s unknown whether this happens because the opportunities or needs are different, or because tool use is unlikely to be invented or maintained.

The Issa Valley has very distinct wet and dry seasons. Researchers collected meteorological data and camera trap footage of 13 mounds to map the dispersals and predation of termites across time. 

They also copied chimpanzee tools and techniques to do their own termite-fishing trials, at 14 different mounds between 2018-2022.

“When I first visited the Issa Valley, I quickly learned that it was more difficult to termite fish than I had expected,” says Seth Phillips, a PhD student in the Anthropology Department at the University of California Santa Cruz (UCSC) in the US.

“It alerted me to the idea that effective foraging for these termite prey might be more complicated than people commonly understand it.”

Of all 1,924 attempts by the scientists at termite fishing, only 363 extracted termites. 

But the researchers were more likely to be successful as rainfall increased, but only to a point (200mm).

Termite dispersal flights only took place in the wet season. Most mounds were most active between 50-200mm of cumulative rainfall but stopped almost completely after 400mm of rainfall.

“We are currently reviewing camera trap footage of the chimpanzee behaviours at these mounds,” says Phillips.

“We want to know how chimps adapt their searching behaviour according to seasonal changes. For instance, do they investigate termite mounds directly after rainfall after a long dry spell? This data could say something interesting about their foraging cognition as related to tool-use.”

Chimpanzees were among the most frequently recorded predators at termite mounds during dispersal flights and often arrived carrying a tool.

Senior author of the study Dr Vicky Oelze, of UCSC, says that the results set up an interesting hypothesis about wild chimpanzee foraging cognition.

“Though we can never read a chimpanzee’s thoughts, we can perhaps start to get an idea of their expectations of resource availability by analysing the instances in which they arrive at termite mounds and investigate them for fishing viability.”

Understanding the ecology of these termites is important baseline information when forming hypotheses and designing new studies into chimpanzee culture, tool-use, and foraging cognition.