Three asian elephants playing, one reaching its trunk towards the camera

Elephants can draw on their keen sense of smell to compare quantities of treats. Credit: Jeff Hutchens/Getty

Neuroscience

Elephants have a nose for portion size

Pachyderms use their trunks to discriminate between two hidden food piles of unequal size.

Elephants can judge quantities of food using only their sense of smell — a talent that might be unique.

Birds and mammals tend to rely on vision to assess amounts. Given a choice between two unequal piles of food, chimpanzees and birds eyeball the piles and eat the larger one.

Joshua Plotnik at Hunter College, City University of New York, and his colleagues presented Asian elephants (Elephas maximus) with two buckets, each holding a different quantity of sunflower seeds that were hidden from sight. After using their trunks to give each a good sniff, the animals tended to pick the bucket with more seeds.

The bigger the difference between the buckets, the more likely an elephant was to choose the one that held more seeds. This rule held true no matter how much the experimenters varied the amounts in each bucket.

Such a finely tuned sense of smell for food has never previously been documented. The next question, the authors say, is how the elephants achieve the feat.