In a revelation that destroys yet another cherished notion of human uniqueness, wild chimpanzees have been seen hunting bushbabies with spears. It is the first time an animal has been seen using a tool to hunt a vertebrate.
Many chimpanzees trim twigs to use for ant-dipping and termite-fishing. But a population of savannah chimps (Pan troglodytes verus) living in the Fongoli area of south-east Senegal have been seen making spears from strong sticks that they sharpen with their teeth. The average spear length is 63 centimetres (25 inches), says Jill Pruetz at Iowa State University in Ames, US, who observed the behaviour.
And the method of procuring food with these tools is not simply extractive, as it is when harvesting insects. It is far more aggressive. They use the spears to hunt one of the cutest primates in Africa: bushbabies (Galago senegalensis).
Bushbabies are nocturnal and curl up in hollows in trees during the day. If disturbed during their slumbers – if their nest cavity is broken open, for example – they rapidly scamper away. It appears that the chimps have learnt a grizzly method of slowing them down.
Chimps were observed thrusting their spears into hollow trunks and branches with enough force to injure anything inside the holes, Pruetz’s research team says. The chimps used a “power grip” and made multiple downward stabs – much the same way as a human might wield a dagger.
Ten different chimps in the population were observed to perform this behaviour in 22 bouts. In one case the researchers saw a chimp remove a dead bushbaby and eat it.
The Fongoli chimps inhabit a mosaic savannah – patches of grass and woodland – where there are no red colobus monkeys. The absence of these monkeys, which are the favoured prey of several other chimp populations, may explain the Fongoli chimps’ unique spear-hunting behaviour.
“Given the lack of opportunity, Fongoli chimps have come up with a way to get around the problem of how to get protein in their particular environment...using tools to hunt,” says Pruetz.
Oh, and that mention of bushbabies being one of the cutest primates in Africa is no joke: