By Victoria Gill Science reporter, BBC News
10 January 2017
Researchers have used camera traps to film tool-use that is unique to chimpanzees in Ivory Coast.
The footage revealed that the clever primates habitually make special water-dipping sticks - chewing the end of the stick to turn it into a soft, water-absorbing brush.
Primate researchers examined the "dipping sticks" and concluded they were made specifically for drinking.
Lead researcher Juan Lapuente, from the Comoe Chimpanzee Conservation Project, in Ivory Coast, explained that using similar brush-tipped sticks to dip into bees' nests for honey was common in chimpanzee populations across Africa.
"But the use of brush-tipped sticks to dip for water is completely new and had never been described before," he told BBC News.
"These chimps use especially long brush tips that they make specifically for water - much longer than those used for honey."
The researchers tested the chimps' drinking sticks in an "absorption experiment", which showed that the particularly long brush-tips provided an advantage.
"The longer the brush, the more water they collect," said Mr Lapuente.
"This technology allows Comoe chimpanzees to obtain water from extremely narrow and deep tree holes that only they - and no other animal - can exploit, which [gives] them a superb adaptive advantage to survive in this dry and unpredictable environment."