Elephants May Sniff Out Quantities with Their Noses


Veronique Greenwood, The New York Times

Date Published
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Elephants keep surprising us.

They live complex social lives, cooperate, show altruism and grieve their dead. And now in the latest evidence of their sophisticated cognitive abilities, elephants appear to be able to distinguish relative amounts of food merely by smell, researchers say. 

The finding, reported Monday in Proceedings of the National Academy of Sciences, suggests that elephants’ olfactory worlds are richer and more informative than ours.

Many tests of animal cognition rely on vision — an elephant or a crow is shown, say, two buckets with different amounts of food, and prompted to choose between them. Some species do quite well at this task, suggesting they can make visual estimates of quantity. Others don’t seem to notice the difference.

But such visual tests overlook that other senses, like smell and hearing, may be even more important to how some animals navigate the world.

Elephants raise their trunks up like a submarine periscope to sniff their environment, potentially gathering information to aid in decision making, said Joshua Plotnik, a professor of psychology at Hunter College in New York, an author of the new study.

To see if elephants could distinguish different amounts of food using only scent, Dr. Plotnik and his colleagues devised a series of experiments that were performed at the Anantara Golden Triangle Elephant Camp and Resort in Chiang Rai, Thailand.

Six Asian elephants were presented with pairs of plastic buckets, one of which had more sunflower seeds than the other, in a range of ratios. The buckets were covered with lids that the elephants could not see through, but with holes that smells could escape through. The elephants were allowed to choose one bucket to open and eat.

As researchers analyzed the elephants’ selections, they found something surprising in some of the tests.

“Remarkably, when we put two different quantities in the buckets, the elephants consistently chose the quantity that had more over less,” Dr. Plotnik said.

The larger the difference between the two quantities — say, 30 and 180 sunflower seeds presented side by side, in contrast with 150 and 180 — the better the elephants were at picking the larger amount.

For some of the tighter ratios, the elephants did not succeed more than half the time, suggesting that the magnitude of the difference between the buckets is important.

Additional tests ruled out the possibility that the elephants were responding to the experimenters’ body language, residual odors left in the buckets from earlier trials or the height of the seeds in the buckets.

How elephants might be able to tell how much food is present using only their senses of smell is still a mystery, said Dr. Plotnik. But he speculates that they may have different ways of getting information from smell than humans: For our part, we can’t say whether a bread box has a whole loaf or a single slice by sniffing the outside, though we might be able to tell there is bread inside.

Understanding how elephants use smell to find food may have profound implications for conservation of these highly endangered animals, Dr. Plotnik said.

In Thailand, conflict with humans often arises when elephants leave protected areas to seek human crops. Could it be that they are responding to a higher concentration of food odors from crops, or some other olfactory cue?

Currently, most strategies for avoiding human and elephant conflict rely on frightening elephants away, rather than using some understanding of their behavior.

“You put up an electric fence to keep an elephant away, you shoot firecrackers over their heads — the whole point is to try and physically prevent elephants from getting to human habitat,” Dr. Plotnik said.

A better knowledge of how elephants find and make decisions about food may result in more effective approaches to keeping them in protected areas.