Reporting findings that help shape our understanding of how tool use has evolved among primates, researchers have discovered evidence that chimpanzees, at least under some conditions, are capable of habitually fashioning and using tools to hunt mammalian prey. The work, reported by Jill Pruetz of Iowa State University and Paco Bertolani of the University of Cambridge, will appear online in the journal Current Biology on February 22nd.
Chimpanzees are well known for their ingenuity in using tools for some tasks, such as obtaining invertebrate insects from logs or pounding open hard nuts, but there had been only fleeting evidence of chimpanzees brandishing tools for bona fide hunting.
In the new work, researchers observed tool use in hunting by the Fongoli community of savanna-dwelling chimpanzees (Pan troglodytes verus) in southeastern Senegal. Chimpanzees were observed making spear-like tools in a step-wise fashion, and subsequently using them with jabbing motions in an apparent effort to obtain lesser bushbabies (Galago senegalensis) from cavities in hollow branches or tree trunks. Bushbabies are nocturnal prosimians that retire to such hidden cavities during the day.
Although there was only one successful attempt in 22 recorded instances of the chimpanzees using the spear-like tools to find and obtain prey, the researchers observed that tool-crafting and associated hunting behavior was systematic and consistent, suggesting that it was habitual. The hunting behavior included forceful jabbing motions into branch or trunk hollows, and chimpanzees were seen to subsequently open the hollows by breaking wood off from a distance, suggesting that the jabbing actions were intended to immobilize bushbabies, rather than rouse them from their cavities (bushbabies move quickly and might otherwise easily evade chimpanzees once roused).