The orang-utans could not reach the peanut, but they wanted it very much. All five orang-utans realised quite quickly that they could spit water in the cylinder which would bring the peanut in their reach.
The primatologists were impressed: it seems that the orang-utans have been thinking in a quite abstract manner. First the primates tried to reach the peanut by hitting, shaking or biting. They needed an average of nine minutes to come to the idea of spitting water. In the next tests they knew the trick and used it right away. The researchers find it unlikely that the animals have seen a comparable trick before.
The water machine from which they took the water to spit in the cylinder was not visible from the place where the cylinder was situated. The monkeys normally drink from this machine. When the test was performed with an empty cylinder, the monkeys came up with the same solution, therefore the water could not have put the idea in their heads.
Only the performance of some corvidae seem comparable to the water trick. The Caledonian crow sometimes uses hooks of bendable iron wire, a material previously unknown to the animal, to fish food from a tube. But the primatologists believed that the solution of the orang-utans was on abstracter level. They did note that a literary crow once did a similar trick in a fable of Aesopus. Dying of thirst, the crow saw a high cup of water. It would not reach the water. Then it kept on throwing stones into the cup until the water level was high enough to drink.
Clever orang-utans surprises primatologists
05september2007
In Leipzig Zoo, primatologists of the Leipzig Max Planck Institute for evolutionary anthropology conducted a research with five orang-utans. The results are published in the scientific journal Biology Letters. The primatologists offered the orang-utans a plexiglass tube with some water and a floating peanut.
