Ants That Can Count 162
Posted
by
samzenpus
from the ants-plus-math-equals-doom dept.
from the ants-plus-math-equals-doom dept.
thisIsOdd writes "NPR had a recent report about scientists at the University of Ulm who suggest that ants in desert environments count to help them get to and from their homes. Because the desert's windiness and sandiness is not conducive the 'smell-trail' method, where ants squeeze certain glands that leave a chemical trail, scientists were puzzled by the fact that these desert ants were able to leave and successfully return to their nest. The theory is called the 'pedometer theory,' and the experiment used to test it involves manipulating the leg length of some of these ants. Ants with longer legs would pass the nest on the way home, and ones with shorter legs came up... well... short."
This doesn't prove ants can count (Score:5, Interesting)
If the experience results are valid, there is still a difference between counting and remembering and reproducing a sequence of movements.
Ants might remember that they have to do "step step step step step step step step" to get back to their nest without actually counting. This would seem much more natural to me.
Here is an example applicable to humans: As a drummer, I can create and reproduce the same roll on the fly. But if you asked me how many times I hit the drum pad, only then I would have to count. I did not need to count in order to reproduce the roll nor did I know how many times I actually hit the drum pads.
This leads me to believe ants cannot count, why would they need to. Counting is good for humans in order to trade, so they have developed that capability. Same goes for female animals that could notice one of their puppy is missing. They don't have to "count" them, they only have to remember a picture of all the puppies and notice the picture they now see is different from the normal picture. There is many more examples you can think off where one can appear to count without actually doing so.
Re:This doesn't prove ants can count (Score:5, Interesting)
Been quite a while since I played drums, but I still remember having to learn how to reproduce certain sequences, and that involved counting the number of repetitions.
I can't remember what it's called but the one where you emphasise every third hit (i.e. HIT, hit, hit, HIT, hit, hit etc) came quite fast, and I can still do that one without even trying (including alternating between 2nd, 3rd and 4th). The one that has every fifth hit (HIT, hit, hit, hit, hit, HIT, hit, hit, hit, hit) is one I never got the hang of, and I remember spending a LOT of time trying to burn it into my muscle memory.
But the 3rd one, while easy, still required learning by counting "ONE, two, three, ONE, two, three" for quite a while.
My point is, when you get really really good at something, like drumming, you don't count at a concious level, but in order to get that good, you did need to count.
How many steps before register overflow? (Score:3, Interesting)
I can think of a number of follow-on experiments to tell us more about this mechanic.
First I think you'd want to establish more conclusively that it is counting or memory of steps or actions, and not something in the environment:
- Replace the sand behind them on their path and see whether they can still get back.
- Put them on a treadmill to get to their location and back so that their aren't actually moving relative to the earth and see whether they still get back.
- Once this get to the food, rotate the artificial section of ground it is on 180 degrees and see whether they still get back.
- Change the wind direction in an artificial environment and see whether they can still get back.
- Reverse the location of the primary light source in an artificial environment and see whether they can still get back.
Then explore the limits of the counting or action memory mechanism:
- Keep extending the number of steps to get to food until they can't remember how many steps to get back.
- Keep extending the number of steps in a path with a turn in it, on each side of the turn, and compare to the path with no turn.
Homing in (Score:3, Interesting)
Quote: "Celestial cues, such as the sun or patterns of polarized sky light, appear to have no detectable effect in the precise homing orientation of foragers of Paltothyreus tarsatus. Field and laboratory experiments reveal that canopy patterns are a major influence in the home range orientation of this ponerine ant, a common species in African forests. Canopy orientation appears to be well suited to the restrictive lighting conditions of tropical forests."
c.f. [sciencemag.org] Canopy Orientation: A New Kind of Orientation in Ants; BERT HÖLLDOBLER, 1980
Quote: "Cataglyphis bicolor, an ant widely distributed in North Africa and the Near East, orient to the sun as well as to visual patterns of the environment. These two mechanisms can be separated. Foraging ants (hunters) orient to terrestrial cues as long as possible, and only after these have become ineffective do they switch over to the menotactical sun orientation. In the digging individuals, however, the visual knowledge of locality is significantly inferior to that of the hunters. Diggers vary considerably in size, but hunters belong to the largest size group. In addition, the largest and smallest individuals orient differently toward black and white areas and stripe patterns."
c.f. [sciencemag.org] Homing in the Ant Cataglyphis bicolor; Rudiger Wehner and Randolf Menzel, 1969
How to become an expert 'in ants' these days?
CC.
Re:Experimental set-up raises a few questions (Score:5, Interesting)
Well, that might be a good explanation for the reason the short legged ants failed to arrive home. However, it doesn't explain why the artificially leg lengthened ants overshot their nest. I mean, if it were you or me, we would have seen our home and stopped, so the ants must really heavily rely on step counting.
Counting or timing? (Score:3, Interesting)
Which brings us to the question: Are the ants really counting steps or is it based on timing?
Because you could get a similar result if it's based on timing. For example the ant walks to point X and it takes 60 seconds, so on the return journey, somewhere in the ants brain there's a countdown from 60 seconds (or more likely a increase/decrease in "potential"). With longer, but not much heavier legs the ant could still overshoot the nest because it's moving faster.
So what if you increased the slope so that the ant slowed down (or sped up) while taking the same number of steps for a particular distance. Would that change where the ant started looking for the nest? The difficulty is the ant could compensate for that - if something takes longer the "meter/timer" could be paused.
Also there's a more "analog" way of counting and there's a more "digital" way of counting.
Digital is the hard edged "1, 2, 3" count. Analog would be closer to filling a pool with buckets of water when counting up and emptying it when counting down.