h a l f b a k e r yPoof of concept
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If you ever had a spare moment and watched ants tracking the scent of an ant trail, you will see that they criss-cross the path, sometimes losing the scent and then picking it back up again.
I wondered how ants knew which way to go? If they came to a path at an angle, they seemed to very quickly
decide the right direction. Left or Right?
I see two possibilities:
1. The trail gets weaker in one direction. This doesn't make much sense as the ants are going along it in both directions. I presume they re-mark the trail as they go, but how do they do it in both directions with the right reduction in strength?
2. The trail is coded.
Imagine the ant leaves a series of dots on the ground. The dots need to be deposited with the right code or it would read the same in both directions.
For example:
dot - space - dot - space - dot - space - dot, reads the same in either direction. Let's abbreviate it using Morse code:
.-.-.-.
So what is the shortest, most easiest code that surely defines the direction?
I propose:
.-..--
But it seems strange to think that ants can lay down scent like this.
Maybe more than you wanted to know.
http://www.ted.com/...rdon_digs_ants.html
[2 fries shy of a happy meal, Jan 17 2013]
What's the gradient in this case?
http://www.youtube....watch?v=nGlzoT0sLaM
(Ant mill) [Ling, Jan 17 2013]
An even bigger ant mill
http://www.youtube....watch?v=prjhQcqiGQc
Quite incredible... [Ling, Jan 17 2013]
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I think I once read that the second ant, following the explorer, also adds to the trail. And so does the third ant. The net effect is that the trail becomes narrower and stronger in the direction that the most ants go, making it relatively easy for the nth ant to follow (also adding to the trail). |
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[zen_tom], I think there must be a little more to it. The [2FSOAHM] link shows that some sort of high five goes on between the ants when they meet. But check out the ant mill...
There is little of the antenna touching, and yet they are all going in the same direction. |
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[Vernon], understood, but how does that show *direction* to/from the nest? |
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Well I didn't know the details that [zen_tom] provided. But an ant can almost always follow its own trail back to the nest. If it encounters some other trail from the same nest, while exploring, I suspect it doesn't matter which way it turns. One direction will lead back to the nest and the other won't. |
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I do think ants have enough memory capacity to remember such junctions when they encounter them again, and it may specifically be able to recognize its own trail, distinct from another ant of the same nest. That would certainly help avoiding exploring where it had already gone. |
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//So what is the shortest, most easiest code that
surely defines the direction?// |
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A dot is a dab; a dash is a space and a space is a
space. |
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You can't use 3 'markings'. |
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But if I misread and you meant dash dot dash dot
dash dot, I can string those together and read the
same backwards. |
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Huh? Do you guys seriously mean you can't hear them
talking to each other about where the food source is;
what they think of nest politics, etc.? |
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Ants, and other members of the Order Hymenoptera,
employ a wide range of chemical communications signals. |
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It would be conceivable they lay (and trail from each
individual) a trail of "out" scent or a trail of "home" scent
as they pass along the trail. |
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Maybe, but then if an ant crosses the two parallel
scent trails, how does it know to turn left or right?
Same problem. The strength of scent idea doesn't
fully hold up; how would the strength be varied? Time?
Number? |
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//You can't use 3 'markings'. // Why not? You could
have two chemicals (A,B, gap, A, B, gap), or two
intensities (strong, weak, gap, strong, weak, gap). |
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I'm having trouble with the gradient idea. If a single
ant lays down scent as it forages, then returns to its
track 5 mins later, the difference in strength of the
scent over 10cm would be: |
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Assume scent life is 1 day
Assume ant travels at 1cm/sec
=862m scent length |
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Difference in strength over 0.1m is 1/8620. |
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A quick check and our well developed eyesight is
good to see the difference between around 500
shades of grey *if they are next to each other*. |
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[MB] Fair enough. Sounds even more far fetched than
my proposal. I get the point. |
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However, considering some of the other info, I wonder
if there is just one scent. It doesn't really matter about
gradient or the direction if the ant blindly follows it
and interrogates ants going the other way.
"You have food and I'm foraging" = carry on in this
direction etc. This would work in the nest runs, too,
where the scent trails might be very confusing. |
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//our well developed eyesight is good to see the
difference between around 500 shades of grey//...
but 50 is enough for most purposes. |
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daaaang... ants are the new lemmings. |
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[Zen_tom], thanks for taking the time to explain. It
does sound plausible. By the way, have you noticed
that ants touch antennae of almost all oncoming ants
on the trail? |
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On another point, just out of interest, what *is* the
shortest code, using two states, that can define
direction? I had a go, but I'm wondering if there might
be a shorter one. |
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//what *is* the shortest code, using two states, that
can define direction?// |
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That is a very interesting question. I can't do better
than [Ling]'s. Unless one of the states is '>'. |
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I have a hypothesis, but it's very quarter-baked. Consider a human running at top speed through snow. At first, the footsteps will be far apart, but as the person gets tired, he/she will run slower and leave prints that are closer together, thereby, without "trying" to, naturally indicate a directionality. |
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With ants, it could be the same thing. As an ant walks, its scent muscle pops out and in, leaving dots of chemical when it's out, but the gland/muscle naturally gets tired and, assuming the ant walks at a constant speed, leaves dots more sparsely as it goes; this creates the direction. It's not "intelligence", just a natural biological function of getting tired. |
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I imagine by the time they've walked all the way to the food and eaten their fill, they are totally exhausted (I would be!) and leave almost no scent trail on the way back. So the directionality remains intact. |
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Ants usually don't eat when they get there. They take the
food back to the nest, where it's used by the whole nest. |
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It was probably a pile of ant exoskeletons. |
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[MB] it is quite strange that the example I gave is not
beaten, yet. Beyond my ability to prove it is the
shortest. |
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With a humerous twist, some of the people in South
East Asia go foraging for ants (red tree ants), and their
eggs. When asked if they ever walk around in circles
instead of going home, they said "Only after too much
rice wine". |
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Who's giving the ants rice wine? And why? |
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The answer they give is: "Yes". |
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