Elephants have awesome olfaction (better than dogs): the pachyderms are the only animals to date that can distinguish different amounts of food by smell alone

This is another recent paper from PNAS, and I’ll put the link in the screenshot (pdf here), but I’m not going to report on it in detail. Rather, this is an excuse to show a video that demonstrates the paper’s main point: while some animals can distinguish greater from smaller amounts of food using vision, elephants can do it using smell. This appears to be the first example of the use of olfaction in cognitive tasks by an animal.  You might think dogs have a keen sense of smell, but they fail the smell test used in this paper.

The journal Science gives the video below as well as presenting a short popular summary of the paper.

To conduct the research, scientists presented six Asian elephants (Elephas maximus) at an educational sanctuary in Thailand with two opaque, locked buckets containing 11 different ratios of sunflower seeds, a favorite treat. The elephants could not see how many seeds each bucket contained, but they could smell the contents through small holes in the lids.

The animals chose the bucket with the greater quantity of food 59% to 82% of the time, the team reports today in the Proceedings of the National Academy of Sciences. (Even dogs, with their famed sense of smell, fail this test, other research has shown.)

And there’s a cool bit of stuff about olfactory receptor genes (OR genes), which I discuss in Why Evolution is True because we have many dead ones compared to our relatives. The presence of nonfunctional OR genes that are functional in our relatives can’t be explained by anything other than common ancestry, one of the tenets of evolutionary theory. Here’s more from Science:

The discovery makes sense, the scientists say, because elephants are known to have the highest number of genes associated with olfactory reception of any species (about 2000 versus dogs’ 811). They can distinguish between the scent of Maasai pastoralists and Kamba farmers, and rely on their sense of smell to navigate long distances to find food and water (up to 19.2 kilometers). The researchers hope their findings could help mitigate human-elephant conflicts in Asia and Africa, because wandering herds use odors to decide where to travel; enticing scents might help lure them away from agricultural fields, for instance.

I was surprised at elephants’ smelling ability even though they have those big trunks, as the trunks are used for many other things, like pulling down leaves and fruits. Humans have about 400 active OR genes, versus the 800 in dogs and 2000 in elephants. We also have another 400 inactive OR genes, showing evolution. (We’re a visual and auditory rather than an olfactory species, so the loss of smelling ability probably didn’t cost much.) In dolphins, as you might expect, the bulk of OR genes are inactive, because they have a different way of “smelling” underwater.

But enough didactic stuff. Watch two elephants pass the “smell test” (remember, they err between 18% and 41% of the time). I love the experimental setup, and hope that the investigators weren’t giving any “Clever Hans” signals!


  1. merilee
    Posted June 5, 2019 at 1:35 pm | Permalink


  2. ThyroidPlanet
    Posted June 5, 2019 at 2:21 pm | Permalink

    “The presence of nonfunctional OR genes that are functional in our relatives can’t be explained by anything other than common ancestry, one of the tenets of evolutionary theory. ”

    That almost could work as the title of one of those so-called “memes”

    As for the bucket of seeds – I wonder if they controlled for temperature – being able to disperse volatile aromas. Or perhaps it was something else – looks like I should read the article now.

  3. rickflick
    Posted June 5, 2019 at 2:22 pm | Permalink

    Remarkable finding. I seem to remember that elephants have poor eyesight. Olfaction could be a compensation. This has me wondering what the world would be like if we humans had 2000 olfactory genes in full operation. A windows rolled down drive along a street with many restaurants would probably be very exciting.

    • gravelinspector-Aidan
      Posted June 6, 2019 at 11:40 am | Permalink

      Or overwhelming? Having partaken of herbal cigarettes on more than a few occasions, I do wonder what the effect of some such compounds on the CNS of dogs is. There’s a reason that people put coke and the like up their noses – it connects directly to the brain.

  4. ThyroidPlanet
    Posted June 5, 2019 at 2:46 pm | Permalink


    “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. ”

    IIU, each trial was a choice between two buckets. So they have a 1/2 chance of choosing the larger quantity and a 1/2 chance of choosing the lesser quantity per trial.

  5. Joseph Heled
    Posted June 5, 2019 at 3:43 pm | Permalink

    The researchers should not be in sight, like you pointed out. Someone else needs to do the presentation to the animal, and more importantly, decide which one the animal choose. The short video does clearly show the criteria for that.

  6. insidephotos
    Posted June 5, 2019 at 3:53 pm | Permalink

    And let’s not forget that the elephant is also the only animal with four kneesñ

  7. Posted June 5, 2019 at 4:08 pm | Permalink

    Reblogged this on The Logical Place.

  8. grasshopper
    Posted June 5, 2019 at 5:12 pm | Permalink

    I see that it’s finally time to eat my truffle pig (the one with the wooden leg) and get myself a truffle elephant.

  9. Mark R.
    Posted June 5, 2019 at 5:50 pm | Permalink

    Hard to imagine what kind of world a species with that kind of olfaction experiences. We can somewhat imagine what an eagle sees by using magnifying lenses, but we haven’t learned how to magnify our sense of smell or taste.

    I’m wondering if African elephants are as orfactorily inclined.

    • gravelinspector-Aidan
      Posted June 6, 2019 at 11:46 am | Permalink

      The discussion mentions elephants distinguishing Masai pastoralists from Kamba farmers, and to the best of my knowledge, the Masai only meet African elephants in their roamings. Unless there are Asian elephants in Dar Zoo, and Masai security staff.
      Does Dar have a zoo?
      The Masai have a quite distinctive diet – high in dairy – compared to most African tribes, so it’s no big stretch to impute a distinctive odour.

  10. infiniteimprobabilit
    Posted June 5, 2019 at 5:54 pm | Permalink

    “rely on their sense of smell to navigate long distances to find food and water (up to 19.2 kilometers).”

    Was 12 miles, obviously. We just know that’s been converted to metric by someone with a calculator and not enough savvy to round an obviously approximate figure to the nearest kilometre.


    • rickflick
      Posted June 5, 2019 at 7:04 pm | Permalink

      I subconsciously registered a glitch as I read that. Nice catch.

    • Pierluigi Ballabeni
      Posted June 6, 2019 at 2:57 am | Permalink

      How do you know this? Why would somebody working on elephants in Asia or Africa use US units to report a distance? Furthermore 12 miles equal 19.3 km, not 19.2 (ok, a typing mistake by the journalist is possible). It could be that somebody had measured an actual distance of 19.2 km (GPS tracks your movements with a precision of few meters).

      • gravelinspector-Aidan
        Posted June 6, 2019 at 11:49 am | Permalink

        It probably depends which country you were measuring in. There’s a definite Anglophone/ Fracophone dichotomy in how distances are expressed, IME.
        Fortunately elephants never cross borders without stamping their passports and re-calibrating their pedometers. Well known for it.

  11. Posted June 5, 2019 at 9:06 pm | Permalink

    I wonder what kind of food they used to test d*gs.

  12. Posted June 6, 2019 at 3:23 am | Permalink

    Thought this would be a plug for our Matthew’s forthcoming book on olfaction!

    When is it due out? Next year? Autumn?

    • gravelinspector-Aidan
      Posted June 6, 2019 at 11:50 am | Permalink

      I thought he was also working on one on the French Resistance, and was wondering when that is due out? Maybe I’m out of date.

      • Dominic
        Posted June 7, 2019 at 3:22 am | Permalink

        The other book pending is neuroscience…

        The Resistance is here –

        • Dominic
          Posted June 7, 2019 at 3:23 am | Permalink

          oops! Embedded sorry…

  13. Posted June 6, 2019 at 11:40 am | Permalink


  14. Posted June 6, 2019 at 12:05 pm | Permalink

    Wonderful – and I am reminded of philosopher P. F. Strawson’s discussion of whether we would have a similar concept of “individuals” if we weren’t such a visual creature and similar work …

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