Giraffes make decisions based on statistical information

Can giraffes calculate the odds? A carrot hidden in somebody's fist might seem impossible to locate, but the mixture it came from offers a clue. A handful drawn from mostly carrots is a better prospect than one drawn from mostly zucchini. The challenge is to compare proportions, not simply notice where more carrots are visible.

Álvaro L. Caicoya, Montserrat Colell and Federica Amici offered four Barcelona Zoo giraffes two transparent containers holding different mixtures of the vegetables. An experimenter took a piece from each and presented closed fists; the giraffe chose with its tongue. Crucially, some comparisons held carrot numbers equal, while others held zucchini numbers equal, preventing either simple counting rule from explaining success.

All four reliably chose the better prospect, usually meeting the success criterion within their first twenty trials. Controls argued against smell or unintended visual clues. A harder version, with a partition making some food inaccessible, was solved by only one giraffe, although none had been trained about the barrier. These animals could judge an unseen snack from the mixture behind it; combining that judgement with a physical obstruction was a different challenge.