Chimps make spears to catch dinner
Wooden weapons are a first in animal kingdom.
Chimpanzees can hunt with spears, say researchers who have seen wild chimps in the grasslands of Senegal. The innovative apes fashion weapons from sticks to kill bushbabies.
The discovery was made in chimps living in savannah dotted with trees. This is similar to the habitat in which humans are thought to have evolved, meaning that the chimp's behaviour may shed light on our ancestors' early hunting strategies.
Although chimps are known to use tools to get food — most notably using sticks to 'fish' for termites — the use of weapons to kill prey was thought to be uniquely human.
The spear-fashioning behaviour was seen in a group of chimps (Pan troglodytes) living at Fongoli, Senegal. "I was amazed every time I saw it," says Jill Pruetz of Iowa State University, Ames, who made the discovery with her colleague Paco Bertolani of the University of Cambridge, UK.
The chimps made the tools after finding a bushbaby, a small, nocturnal mammal weighing around 200 grams, asleep in a tree hollow. By tearing off branches and stripping them of bark, and then biting the ends into a point, they made a spear to poke into the crevice.
Although the chimps were seen killing a bushbaby only once in 22 observed attempts, supplementing a diet of fruit and nuts with the occasional bushbaby is clearly worth the effort, says Pruetz, who reports the discovery in Current Biology1.
Only females and young chimps were seen making the spears. "Maybe it's not beneficial enough for the males," Pruetz suggests. "The size of the prey makes it quite a small package of protein."
It's not known whether other chimp populations can make spears. Senegal's savannah chimps — of which around only 500 remain — are unusual. Most chimpanzees live in forest and hunt red colobus monkeys, which are not found in Senegal.
Woman the gatherer
The existence of hunting female chimps with their own distinct style bolsters the idea that human technology followed a similar path, Pruetz suggests. The 'woman the gatherer' theory, first put forward in the 1970s, argues that women might have been the first tool makers.
The finding is another reminder of chimps' impressive brainpower. Only a handful of other species regularly use tools. Some crows hook insects out of crevices using specially fashioned sticks, and a group of dolphins off the coast of Australia use sponges attached to their beaks to disturb prey hiding on the sandy seabed.
But the use of weaponry by the Senegal chimps may represent a new horizon in animal technology.
- Pruetz J. D. & Bertolani P. Curr. Biol., doi:10.1016/j.cub.2006.12.042 (2007).