Fashioning spears and wielding them to hunt – these sound like typical activities of our human ancestors. But the surprising fact is that not only are tool-use and tool-building carried out by other animal species, they’re done in the context of hunting as well. Chimpanzees in the Fongoli savanna of Senegal have been observed1 creating spears out of sticks, using an up to 5-step process that entailed trimming them of leaves and stray twigs, and biting the sticks’ ends to sharpen the points.
Once the spears were made, the chimps would seek out holes and tree trunks where nocturnal bush babies tend to sleep during the day. The chimps would thrust the spears into the holes, then withdraw them and lick or sniff the tips to check for blood. If blood was found on the spear tips, it meant they had been successful in striking a sleeping bush baby – this happened only once out of the 22 hunting attempts observed.
Notably, it was primarily juvenile chimps of both genders who undertook spear hunting during the observation period. Most of the time, it’s adult males who take part in other hunting activities. One reason for this could be that the younger males and females have turned to spear-hunting in order to creating a hunting niche for themselves that isn’t already dominated by the grown males.
When pointing out the differences between humans and other animals, many are quick to claim that only humans will hunt another species to extinction, taking more than they need to survive. Yet again, chimps prove that this is untrue. Red colubus monkey populations in Uganda recently plummeted 89% as a direct result of overhunting by chimpanzees.2 Though the monkeys are more agile, the chimps manage to successfully capture the monkeys and feed on them. Their success rate is similar to that of the bush baby spear-hunters. Chimps specifically target juvenile monkeys who have yet to reach sexual maturity, ensuring that few survive to reach breeding age. The reason behind the overhunting is still uncertain, however, it is noted that the hunting peaks during seasons when other food sources are scarce.3 Then the chimps’ meat consumption ratios become comparable to those of human foraging societies also going through seasonal food shortages.
These hunts are most often social events for the chimpanzees, and are carried out 90% of the time by males (both adult and adolescent). The chimps will also share the meat with those who participate.
The hunting habits of chimps and their discovered use of hunting-tools reveals that they are far more similar to humans than previously thought. By observing the spear-hunting chimps further and documenting the social dynamics involved in their hunts, we can learn more about their aptitudes for human-like behaviors, as well as the evolution of tool-use and the hunting habits of proto humans.
This article is written by Amanda Pachniewska, founder & editor of Animal Cognition.
Sources
1 – Jill D. Pruetz, Paco Bertolani
Savanna Chimpanzees, Pan troglodytes verus, Hunt with Tools
Current Biology
http://www.cell.com/current-biology/abstract/S0960-9822(07)00801-9
2 – J.S. Lwanga, et. al.
Primate Population Dynamics Over 32.9 Years at Ngogo, Kibale National Park, Uganda
American Journal of Primatology
http://onlinelibrary.wiley.com/doi/10.1002/ajp.20965/abstract;jsessionid=65605294E8F8F3CEA9E7BEE3A1672BDF.f01t02
3 – Dr. Craig B. Stanford
The Predatory Behavior and Ecology of Wild Chimpanzees
http://www-bcf.usc.edu/~stanford/chimphunt.html
