Assessing quantity combination and dissociation in giraffes

Can giraffes add but not subtract? In earlier experiments, captive giraffes chose larger food portions, with their choices also influenced by the size and spacing of the pieces. That showed they could judge food amounts, but tracking a portion as it changes requires more than comparing what is in view. The new study investigated whether giraffes could choose the larger portion after watching food being added, removed or moved between containers, with the final amounts hidden.

Iker Loidi and his team tested four giraffes at Barcelona Zoo, showing them starting portions of carrot and letting them watch the changes before choosing a container. In one addition condition, a container began with one piece and another with two. Adding two pieces to the first made the final choice three versus two, so remembering which container had started with more would give the wrong answer. The researchers compared choices after additions with those after removals and transfers.

All four giraffes chose the larger final portion more often than chance after additions, averaging 68% success. None performed significantly above chance after removals or transfers, which does not establish that they were unable to track those changes. Because the experiment did not separate the number of pieces from the bulk amount of food, success does not demonstrate arithmetic. The findings suggest that these four giraffes could update a remembered food amount when they saw more being added.