Ants’ Acquisition of A Symbol for Zero and Its Use to Add

It has been previously shown that workers of the ant Myrmica sabuleti can add up numbers of elements when seeing the result of the operation during training, can acquire multiple numerical symbolisms and can make additions using learned numeric symbols. They have also been shown to acquire the notion of zero through experiences. Here, we examined if these ants can associate a symbol with zero and can use this symbol to add. Working on four colonies, we found that the ants acquired a numerical symbolism for zero, and that they used this acquisition for making the additions 1 + 0, 2 + 0, 3 + 0, 4 + 0. This ability simply resulted from operative conditioning and from the ants’ capability in adding up two amounts sighted side by side. The latter imperative condition shows that ants’ numerical cognitive faculties are at a lower level than that observed in honeybees, in some birds and monkeys.