15 April 2015
Title:New evidence on the tool-assisted hunting exhibited by chimpanzees (Pan troglodytes verus) in a savanna habitat at Fongoli, Senegal.
Authors: J. D. Pruetz , P. Bertolani , K. Boyer Ontl , S. Lindshield , M. Shelley , E. G. Wessling
Journal: Royal Society Open Science
A study in Royal Society Open Science this week finds that female chimpanzees are more likely to hunt with tools than the males, who tend to rely more on their strength and size for catching prey.
The study presents results from Fongoli in Senegal where the chimpanzees hunt their prey with tools. This community is the only known non-human animal to regularly use tools to hunt; chimps in other areas don’t seem to have picked up on the trick. Studying these tool-using primates could give an insight into the importance of hunting in human evolutionary history, filling in some of the gaps in our understanding of how and why our ancestors started using tools.
Meat does not make up a large portion of a chimpanzee’s diet but they regularly hunt small vertebrates like bush babies for valued nutrients. The chimpanzees in the area have been seen snapping off pieces of branches and stripping them down to make spears which they stab into holes in trees where their bush baby prey could be hiding.
The team studying the chimpanzee population found that most of the tool-assisted hunts recorded were carried out by female chimpanzees. Though overall males were the more successful hunters in the Fongoli area, when it came to tool use, females took the lead. Of the 308 hunts the researchers recorded, 175 were carried out by females and just 130 by males. Males led just 40% of the hunts even though on hunting days they made up 60% of the chimpanzee pack.
In other environments adult male chimpanzees are usually seen as the primary hunters so the proportion of female chimps using tools to hunt is an intriguing finding for researchers. One explanation for the difference in tool use between the sexes could be that male chimps tend to be more opportunistic in their hunting than females- sometimes grabbing fleeing bush babies who have managed to evade a female hunter.
The team say it’s unclear why the Fongoli chimps use tools but other chimps don’t. It could be that other chimps never learned the technique or that a particularly socially tolerant environment at Fongoli has led to female and lower-ranking chimps also learning to hunt. In many locations a higher ranking chimp might steal captured prey from a female or low status male, in Fongoli theft of prey is rare. The team say the environmental pressures of living in the hot, dry Savannah and the incentive of keeping nutritious prey might have encouraged these chimps, who could be less able to run down prey or catch them with their bare hands, to learn to hunt with tools.