IT鈥橲 a revelation that destroys yet another cherished notion of human uniqueness. Wild chimpanzees in Fongoli, south-east Senegal, hunt vertebrate prey with spears 鈥� the first time such behaviour has been recorded in a non-human animal. And in another surprising first, the same population of chimps shelter in caves. The more we observe them, the more chimps seem to surprise us.
鈥淚 keep watching for the Fongoli chimps to begin drawing on the wall of the caves,鈥� says Jill Pruetz of Iowa State University in Ames, who led the research.
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In the savannah habitat of Fongoli the chimps, Pan troglodytes verus, often hunt green monkeys, but adult males have priority over access to the meat. So female and juvenile Fongoli chimps have found their own way to procure meat: they fashion short spears, which they sharpen with their teeth, to hunt one of the cutest primates in Africa 鈥� bushbabies (Galago senegalensis).
The way chimps use these tools is very different to the 鈥渆xtractive鈥� way they use sticks to harvest insects. Bushbabies are nocturnal and curl up in hollows in trees during the day. If disturbed they will scamper away rapidly. So it appears that the chimps have devised a grisly method of slowing them down. 鈥淭he chimps use the tools along the lines of a weapon to incapacitate the prey,鈥� says Pruetz.
Chimps were observed forcibly thrusting their spears into hollow trunks and branches, with enough force to injure anything inside. The chimps used a 鈥減ower grip鈥� and made multiple downward stabs in much the same way as a human might wield a dagger. Ten different individuals were seen performing this behaviour in 22 bouts. In one case the researchers saw a chimp remove a dead bushbaby and consume it (Current Biology, DOI: 10.1016/j.cub.2006.12.042).
鈥淚mmatures and females are innovative in solving the problem of feeding competition,鈥� says Pruetz.
Fongoli chimps have another unique habit: they shelter in caves during the heat of the dry season. It鈥檚 significantly cooler in the caves, says Preutz, who will publish this study in a forthcoming issue of Primate.
鈥淏ack to the drawing board again in terms of trying to define how humans are special,鈥� says Pruetz.
