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Elephants have a nose for quantity

Significance Although many animal species have demonstrated an ability to differentiate between more and less when presented with different amounts of food, they have done so primarily using vision. In this study, by contrast, elephants showed that they can detect differences between various quantities of food using only their sense of smell. Thus, elephants may be unique in their use of olfaction in cognitive tasks. This research suggests that it is important for psychologists to incorporate into experimental designs the ways in which different animals interact with their environment using all of their senses. Such species-specific paradigms would ensure comparisons about cognition across taxa are fair and relevant. Animals often face situations that require making decisions based on quantity. Many species, including humans, rely on an ability to differentiate between more and less to make judgments about social relationships, territories, and food. Habitat-related choices require animals to decide between areas with greater and lesser quantities of food while also weighing relative risk of danger based on group size and predation risk. Such decisions can have a significant impact on survival for an animal and its social group. Many species have demonstrated a capacity for differentiating between two quantities of food and choosing the greater of the two, but they have done so based on information provided primarily in the visual domain. Using an object-choice task, we demonstrate that elephants are able to discriminate between two distinct quantities using their olfactory sense alone. We presented the elephants with choices between two containers of sunflower seeds. The relationship between the amount of seeds within the two containers was represented by 11 different ratios. Overall, the elephants chose the larger quantity of food by smelling for it. The elephants’ performance was better when the relative difference between the quantities increased and worse when the ratio between the quantities of food increased, but was not affected by the overall quantity of food presented. These results are consistent with the performance of animals tested in the visual domain. This work has implications for the design of future, cross-phylogenetic cognitive comparisons that ought to account for differences in how animals sense their world.