Orang-utans reach new level in water study

Orang-utans reach new level in water study
04/07/2007
Telegraph UK

Video: Orang-utan uses water to solve problem
http://www.mediaplayer.telegraph.co.uk/?item=2CD98F0B-E73C-42C6-8FA2-36F0F065268C

A great ape has been shown to use water as a tool for the first time, in the latest demonstration of their remarkable problem-solving skills. To obtain the peanut, orang-utans had to spit water into the tube to raise the water level.

The discovery was made when orang-utans took part in a pioneering experiment that was inspired by the ancient Aesop's fable in which a thirsty crow tossed stones into a pitcher to raise the level and drink the otherwise inaccessible water.

The experiment in Germany, described today in the Royal Society journal Biology Letters, details how one group of orang-utans had sufficient mental insight to "invent" the use of water as a tool to obtain a tasty treat.

Natacha Mendes, who undertook the study with colleagues Daniel Hanus and Josep Call at the Max-Planck-Institute for Evolutionary Anthropology, reports how five orang-utans at nearby Leipzig Zoo used water when they were confronted with an out-of-reach peanut floating inside a vertical, transparent tube.

To obtain the peanut, orang-utans had to collect water from a drink dispenser and spit it into the tube to raise the water level. For them to be able to reach the peanut, they had to repeat this three times.

Miss Mendes told The Daily Telegraph: "We wanted to know whether they could solve the problem by coming up with a different strategy from the usual ones, such as reaching with their hands, biting and pulling the tube or using sticks. This is the first time that someone has recorded liquid tool use by mammals."

It took the apes about nine minutes on average to solve the problem. And once they had the knack, the apes stuck to spitting water.

"As soon as they saw the change in water level, they figured out how to solve the problem," Miss Mendes added.

The team points out that in this experiment the tool - water - was doubly unusual in that it was not solid. This demanded more abstract thought on the part of the apes. This water test could mark an important new way to test the flexibility of the mind of apes and other creatures.

"As far as we know," Miss Mendes said, "no such flexible behaviour in the tool-use domain has been reported in other species, including corvids [crows], which have been challenging great apes' performance in several aspects of problem-solving."

Recent research suggests that apes are given a run for their money by clever crows - the Einsteins of the bird world - which have been shown to be able to make nifty tools out of leaves and evolve designs.