ant logi(sti)cs – what happens when an ant colony decides to move?

Last night, me and my partner arrived at my parents-in-law’s farm in Morocco. The weather is wonderful and the food terrific – it’s always a treat being here! After we woke up to the call of the rooster, we put our boots on and went for a walk. It’s great going out here because there’s so much life! I’m especially fond of the insect life; compared to Finland, there is an incredible richness of species. It almost makes me dizzy, in a very happy way!

Some of my favourite insects are of course ants (they were my experimental organisms for my master’s project). Walking around on the farm, you can see them basically everywhere, doing what ants do – collecting food, cleaning the nest entrance, defending the nest. What we got to see this morning was another one of those things that ants do, but not every day: they were moving. Moving to a new place is no small feat when it comes to ants: after they’ve found a new place that suits them, they have to move all their stuff there, too, not just themselves. That stuff is the young of the colony: eggs, larvae, pupae and newly eclosed (hatched) individuals, both workers, queens and males.

I want to give some very short background on ants and their biology, since it might help you understand the effort it takes and the dangers they face when they decide to move. Ant colonies consist of one or a few queens, who are the reproducing females in the colony, and workers, who are also female but don’t reproduce. Instead, the workers do everything else in the colony. Always when you see ants running around, they’re female. Occasionally, there are also males, but they usually live only for a few weeks: they’re born, they mate, and die almost instantly after mating.

The size of the colony can range from tens of individuals to millions. A queen mates only at one time during her lifetime (possibly with more than one male) and stores the sperm from that mating for the rest of her life. She can live up to 30 years, and continues using the sperm acquired during that one mating flight to fertilize all the eggs she lays during her whole life. Most of her offspring are workers who build the colony, maintain it, defend it from invaders, take care of the developing young (from egg to larva to pupa and finally an eclosed adult), collect food and feed the queen. During a move, it’s of course these individuals who make it happen and usually also carry the queen to the new nest. The young are carried one by one in the workers’ jaws.

Moving is a risky business for ants. Ant larvae and pupae are full of nutrition and lack jaws or stings and are thus the favourite food for many animals. Transporting them from one nest to another means that they have to be taken from the dark and safe depths of the nest up to the surface during daytime.  This, of course, is literally bringing otherwise difficult-to-get, nutrient-rich food into broad daylight.

So why do they do it? There are many reasons, but in the end, it’s because the old nest has become unsuitable in some way: maybe it’s too dry or too small or maybe it’s infested with some parasite (like a fungus). There’s no way of knowing why this particular colony decided to move, but since it’s not an everyday activity, I decided to take some pictures of the event (I have to say here that it was actually my partner who first saw this happening and pointed it out to me – and even though he’s a great photographer himself, he let me do the photographing). You can see some of the photos here. I hope you enjoy them – also, if you have any questions or comments, feel free to ask or comment!

This ant is carrying a pupa. 

You can already see that the eye of the pupa is darker than the rest of the ant – as the ant ages, its exoskeleton melanises and becomes dark.

Someone also has to guard the situation and defend the workers carrying the young, if needed. Ants are very efficient at division of labour: during a move, some do the carrying and some do the guarding. 

This worker is gently carrying a larva in its jaws. It’s quite interesting to think how a bag of liquid (the larva) will be a fully capable worker after a few weeks.

It was interesting to watch the ants climb over obstacles several times higher than themselves, while carrying a load that sometimes weighed almost as much as themselves. Here’s another worker with a pupa.

Unfortunately, I didn’t manage to get a good picture of a worker carrying eggs… But if you use your imagination, maybe you can see that this worker does have a bunch of eggs in its jaws. It’s fortunate that they stick together; moving all the eggs one by one would probably take a huge amount of time…

This worker seems to be carrying another adult ant. The workers don’t usually carry other workers to the new nest, but the individual being carried also doesn’t look like a male or a queen. If you look closely, though, you can see that the ants look quite different – one has much more hair than the other, for instance. This might mean that the ant is actually dead and is moved because it’s part of the colony’s food storage. Some ant species also enslave other ants, but during a move, those slaves would probably walk by themselves to the new nest. I don’t know exactly what’s happening here, but there were many of these adult ants being carried to the new nest. I’m happy to hear suggestions!

[EDIT: I was wrong – apparently worker ants do often carry other workers to the new nest, because it’s energetically less costly for an ant to carry another than for two ants to walk separately! Alex Wild kindly directed me to the wonderful book The Ants, where this behaviour is explained… You learn something new every day!]

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34 thoughts on “ant logi(sti)cs – what happens when an ant colony decides to move?

      • I just witnessed this phenomena in my own backyard. Millions ( seemed like that anyway ) of ants marched across my patio all day long , some carrying white things which I now know could have been eggs, or pupae or an almost developed ant. It took them hours and was all very organized. They then crossed the back of my house at which time this seemed to disappear under my basil plants. They came from another place too , a hole in the side of our house, and they joined the column of moving ants. The next day it was over. Not a sign f them .The last thing I saw was one ant gong one way and another going back toward the origin point. They met and touched each other as if to say, yep, looks like we got everything – nothing left behind.

  1. Pingback: How does an ant colony coordinate its behaviour? « Inspiring Science

  2. Pingback: my favourites from the year gone by! « alternative viewpoints

  3. I would think that the Adult that is being carried would be a dead ant that is part of the food storage. I have seen this many times.

    • Yeah, that is also a possibility, certainly. Are you sure they’ve been dead? It has also been shown that the workers do sometimes carry each other to save energy.

    • I’m afraid I don’t know. I would assume that it’s not at the very beginning, as I don’t think she’d (or they – oftentimes, there are several queens in a nest) be left alone in the new nest, or the old one for that matter. If I find something out, I’ll get back to you! 🙂

    • After having consulted with my ant researcher friends, this is what I found out:

      Queens (generally – there are certainly differences between species) usually move to the new nest site during the middle of the relocation process. Most of the time, they aren’t carried, but walk to the new site, surrounded by workers. This is how one of the researchers described it:

      “After a worker discovered a suitable new nest site, she would first do several tandem runs with other workers to show them the new nest site. After this initial recruitment, the workers started carrying brood, roughly starting with the pupae (most valuable?), then larvae, and then eggs. At the height of the move, they also started carrying workers (as you saw) AND that was the point when the queen(s) also followed to the new nest site.”

      I hope that answers your question! 🙂

      • Oh that is so fascinating. This just happened in my backyard for the second time in as many months and I wanted to confirm my suspicion that what they were carrying was eggs and larvae, and I ended up with even more interesting information. I never would have guessed that it would be energetically more efficient to carry another worker than to walk separately. Ants are kind of amazing.

  4. I’ve been watching this happen on my porch today. It’s fascinating. Thanks for the pics and info. I have he same question as clay about the queen.

  5. Hi!
    I am working on a school project with TfL(Transport for London).
    I would like to ask you how ants move their larva in details.

    Is there any rule or specific time that ant moves their larva?

    If you can e-mail your thoughts I will be very appreciated.

    My e-mail is: function.aesthetic@gmail.com

    Best,
    Chee

    • I was watching the ants and on attempting to catch the egg-carriers, the non-carriers came to attack the thing that was posing a threat. I noticed that the ants stopped and went around the blockage. When I had them in captivity, they dropped the eggs and didn’t care much. Only a few minutes later did they check on the eggs.

    • Hi!

      To start a colony, you need a queen who can produce more eggs and workers. The 5 ants you caught might be able to take care of the larvae and help them hatch, but if you end up with only workers, you won’t be able to get a colony.

      Keeping an ant colony is not necessarily very easy, either. It depends a lot on the species, how they live in nature and how sensitive they are. Some ants live very happily in captivity, whereas others can’t even survive.

      Good luck!

  6. I’ve been watching the marching ants go over a specific trail on the edge of my patio. I know where they are going but haven’t found where they are coming from. There also seems to be like millions of them going back and forth. They have been carrying various things like larvae, seeds, the dead and no telling what else. They have been doing this for a week!! How long do you think this transfer will take place?

    • A week is quite a long time! Some ants move more regularly, whereas others only move if they have to. It sounds like the colony might be quite big. Are they done with the move by now?

    • I have beem watching ants move in my backyard for a week. They moved once and are in the process of moving again to the other side of the yard. They do their test run for days before moving the babies. It’s wild…once they start moving the babies it’s like they go into a trance. I love it!

  7. While hiking the Tahoe Rim Trail my husband and I observed ants carrying these “white things” and wondered if they could be moving. In my search for more information I came across your very interesting and informative post. We did witness an ant colony moving! Thank you for sharing your insight!

  8. this same process seems to be occurring in my house…. raised my clothes basket to find what appeared to be a whole colony under it… most were carrying the little white bundle …. i just placed the basket back and they eventually all settled back under there …. dont want to hurt them but need to move the basket… it has been super hot the past week here… and they are feeling it too… they are everywhere there is water… even in the electric kettle!! any advice on how to get them out…. ty 🙂

  9. My wife and I were curious about the ant migration in our garden and came across your super informative description and wonderful pictures. Many thanks for this insight into the habits of my favorite insect!

  10. I watched an ant migration yesterday. Reddish, about 1/4″ long, carrying something small and white. They moved into an ant hill which was inhabited by smaller black ants all summer. Were they invading? Or could they have all been one group, eventho different colors and sizes. Fascinating, I watched the process for al least an hour – over rocks, down a sidewalk, across a parking lot then across my lawn to the new home.

  11. It’s absolutely amazing to watch ants moving a colony. My husband thinks I’m crazy but I could watch them all day. I try and protect them and won’t let him cut the grass. It’s just a beautiful part of nature.

  12. I’m all for nature. Although, we just moved to GA. The ants here are ridiculous! Yesterday we picked up our car, it has been sitting for 4 months. It had a colony of ants in it. After my husband drove our care home the colony was moving to the truck. I saw many caring the white pula. How does a colony of ants make an old car their home. A better question how to I make them move? My husband tried to get most of them off but they keep coming out.

  13. Hi! Great pics and congrats on the long running thread! I just witnessed a move or an enslavement, I’m no expert, but I figured out what they were doing to an extent. I found it fascinating. They were moving about 200 feet, as I found their point of departure and their new home. As a layman, I was captivated and watched them on and off for hours. Such busy little things! What I’m curious about though, is that at some point some of them started carrying the larva/pupae back to the original point of departure. Any ideas why? Could the new place have filled up? Could the queen (like many human ladies heh heh) have decided she was not liking the arrangement and directed them back home? Humans only have to move the shelving unit a few feet either way at the direction of the ‘queen’, but this was definitely more involved for the ants I’m afraid. They all didn’t go back, but a good number did, passing ones carrying the young going forward to the new nest. I’m just curious and eagerly await any reply you might have. Thank you again for the wonderful post and pics! -Ivan

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