In 1913, Köhler left Frankfurt for the island of Tenerife in the Canary Islands, to be the Director of the Prussian Academy of Sciences anthropoid research station. Here, Köhler observed how chimpanzees solved problems, such as that of retrieving bananas when placed out of their reach. They stacked wooden crates to use as makeshift ladders, in order to get the food. If the bananas were placed on the ground outside the cage, they used sticks to lengthen the reach of their arms.