Note from Con Slobodchikoff: This is a post by guest author Randall Johnson, who has contributed a number of posts to this blog and to the Dog Behavior Blog.
Given that RWNB ended 2009 with a post about ants, it seemed fitting to start the New Year with another post featuring these fascinating insects.
A study done by German scientists, led by Harald Wolf, professor of neurobiology at the University of Ulm, suggests that desert-dwelling ants may have "pedometer-like" cells in their brains that enable them to count their steps and that they use this unique navigational skill to find their way back to the nest after foraging for food.
But why desert ants? Because most ants live in places that allow them to lay a scent trail on the ground that show other ants how to get to food and back home. Scent trails, however, don't work in the desert; the constantly shifting sand scatters smells almost immediately.
So how do these ants find their way back to their nest with such unerring accuracy? It's already known that ants can use the position of the sun and the pattern of polarized light as a kind of 'celestial compass', but that doesn't explain how they determine distances with such precision.
To try to unravel this mystery, Wolf and his assistant, Matthias Whittlinger, trained two groups of Sahara desert ants to find a food site 10 meters from their nest. While the ants were busy eating, the scientists removed them and divided into three groups.
One group was left alone. The second group had pre-cut pig bristles superglued to each of their six legs, effectively giving them stilts. Ants in the third group had their lower leg segments cut off, thus making each leg shorter. (This part of the experience has since drawn some criticism. It should be noted, though, that in the wild, these segments often dry up and break off naturally without interfering with the ants' ability to walk long distances.)
The ants were then released to make their way back to the nest. The scientists watched to see what would happen. If there really was a step-counting mechanism at work, then the ants whose strides had been altered would have their calculations thrown off.
And that’s exactly what happened. The normal ants walked right up to the nest and went inside. The stilt-leg ants, using giant steps, walked past the entrance and stopped 15 meters away. The stump-legged ants, using baby steps, stopped short of the entrance by almost 5 meters. Yet, all three groups had walked exactly the same number of steps back from the food site.
Interestingly, when the ants went out again in search of food, the two groups with altered gaits had no trouble judging the correct distance back to the nest.
Of course, this doesn't mean Sahara ants are actually counting their steps as "one, two, three, four, five," and so forth, the way we would. More likely, Wolfe explains, there is a neural mechanism at work that converts the motor excitation caused by each stride into a measure of distance.
Still, it's an ingenious solution to not being able to lay scent trails and it shows there is still much to be learned from even the humblest of creatures.
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