Why Chimp Huntresses Love Their Weapons

It sounds like something straight out of Planet of the Apes, and could turn a great deal of what experts thought they knew about chimps on its head: chimps are using tools - like tiny spears - to hunt prey, and it's females who are often bearing these weapons of choice.

Experts have long known that in most chimpanzee groups, adult male chimps are the main hunters and capture prey by hand. This is not unlike how hunter-gatherer tribes worked, according to anthropologists' understanding of humanity's earliest years. And that should be no surprise, as chimpanzees are one of our closest relatives.

However, when tools like small spears and prods were used during hunts, researchers found that it was female chimps who were usually behind this behavior. That's at least according to a study recently published in the journal Royal Society Open Science, which detailed how Jill Pruetz and her research team observed and documented more than 300 cases of tool-assisted hunts.

Pruetz first began to observe more females participating in hunts in 2007 while surveying savanna chimps in Fongoli, Senegal. However, her initial conclusions about this behavior were heavily criticized, often chalked up as nothing more than coincidence.

That's why she set out to bolster her numbers, finding in this latest work that in 305 instances of tool use, a whopping 175 concerned a female chimpanzee huntress. Additionaly, while 60 percent of the hunting groups observed were male, only about 40 percent of hunts with tool use were led by them.

"It's just another example of diversity in chimp behavior that we keep finding the longer we study wild chimps," Pruetz said in a statement. "It is more the exception than the rule that you'll find some sort of different behavior, even though we've studied chimps extensively."

It's important to remember that just like humans and some other primates, chimps are omnivorous. While they pad their diet with extensive fruit consumption, they also eat small mammals. The subjects of these latest observations were hunting bush babies in particular, and it seems that the tool use was part of a larger strategy.

The study describes how a tool user would prod at a galago, commonly known as a "bush baby," with her thin spear, prompting the animal to abandon its hiding spot. A male was then able to dive for the animal, catching and killing it with his bare hands.

Still, Pruetz adds that this behavior is not common, and has only been seen extensively in Fongoli - a potential consequence of social dynamics that divert from the norm.

"At Fongoli, when a female or low-ranking male captures something, they're allowed to keep it and eat it," she explained. "At other sites, the alpha male or other dominant male will come along and take the prey. So there's little benefit of hunting for females, if another chimp is just going to take their prey item."

Still, it's an intriguing find, and one that shows how complicated chimpanzee social dynamics and tool use really are.

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