A Blog by Ed Yong

Army ants plug potholes with their own bodies


Imagine that you’re driving along a country lane. As often happens, the road suddenly transforms from a well-paved street to a pothole-ridden nightmare. As your suspension and your stomachs start to tire, your friends in the back suddenly force you to stop the car.

To your amazement, they jump out and lie across the potholes, beckoning you to drive your car over them. It may seem like a far-fetched scenario, but if you were an army ant, such selfless behaviour would be a matter of course.

An army ant worker plugging a pothole.Army ants are some of the deadliest hunters of South America. Amassing in legions of over 200,000 ants, they become a massive predatory super-organism that fan out across the jungle floor leaving dismembered prey in their wake.

Behind the killing front, the corpses of the ant’s prey are taken back to the nest by foragers. But the route back home is not a smooth one. At an ant’s size, small twigs and leaves can be the equivalent of a bumpy, unpaved motorway.

Scott Powell and Nigel Franks from the University of Bristol found that at least one species of army ant (Eciton burchellii) solves this problem with living paving. Certain workers stretch their bodies over gaps in the forest floor, allowing their food-carrying sisters to march over them.

The ants carefully size-match to the holes that they plug. Powell and Franks stuck planks with different sizes of hole in the path of the ant column, and found perfect matches between ant and hole.

By smoothing the trail home, they ensure that other workers can return food to the colony as fast as possible. Powell and Franks calculated that this increase speed means that the colony as a whole gets more to eat, even thought the plugging ants cannot carry any food themselves.

It may seem that the plugging ants have a hard lot in life. But they are ultimately rewarded for their temporary sacrifices. When the foraging trip finally ends, the pluggers can look forward to a hearty meal when they return home. By taking on a specialised role, these ants improve the performance of the colony as a whole.

Reference: Powell & Franks. 2007. How a few help all: living pothole plugs speed prey delivery in the army ant Eciton burchellii. Animal Behaviour doi:10.1016/j.anbehav.2006.11.005

11 thoughts on “Army ants plug potholes with their own bodies

  1. If human kind is as selfless as the ants, the Earth will be a nicer place to live. It is very sickening to see how human destroying the Earth for their own economic benefits, exploiting others mostly.

  2. Spoken like a true liberal idiot that’s too stupid to realize that the “selfless” army ants are so called because they tend to form massive legions and attack and wipe out other ant colonies. Some species even enslave other ant species. Get a clue.

  3. It is a common mistake to compare ants to human individuals.
    Humans compete with each other for reproduction, most ants in a colony don’t.
    A better comparison would be comparing (worker and other non-reproducing) ants to the white blood cells in your veins, which will attack bacteria without hesitation, though it may lead to their own destruction.

  4. “If human kind is as selfless as the ants, the Earth will be a nicer place to live. It is very sickening to see how human destroying the Earth for their own economic benefits, exploiting others mostly.”
    Come now. I love nature and our earth, but its not very observant to consider the ants as having selfless motives. They are competing for resources just like humans are. Did you read the first part of the article? How they decimate other organisms in their path? I’m very glad that humans have as little in common with army ants as we do.
    On a semi-related note- our need for resources and our willingness to compete for them is why I think sustainability is a necessary factor if we ever want to have peace between humans.

  5. It’s all too true that a common human mistake is our habit of seeing ants as tiny simulacra of humans, while nothing could be farther from the truth. Nowhere is this more apparent than in our misinterpretation of their colonial organization as something analogous to human politics and ideologies—they have been called monarchists, fascists, democrats, and communists by different opinionated researchers throughout myrmecological history, who yet seem unable to agree; yet ants remain ants, and humans anthropomorphizing and/or emulating them will neither improve us or help in us understanding them better. I, in particular, definitely agree with April that ants should not be imitated, due to their violent nature: the renowned Harvard myrmecologist (and founder of sociobiology) E. O. Wilson is credited with quipping that, if ants got hold of nuclear technology and had the capability to use it, the planet would be immediately annihilated in as little as two weeks.
    However, one should definitely note the context: Wilson was not referring to the supposedly violently warlike army ants when he made this quote, but to no other ants than the much-human-beloved “harvesters” (the stars of “A Bug’s Life”), which wage war with each other on an almost daily basis in competition for resources, sometimes even conducting raids on rival colonies in which they slaughter those rival’s brood. (Sounds a bit too anthropomorphic of a behavior, huh?) Army ants, on the other hand, never senselessly attack and kill members of their own species, as jcnnghm so brusquely insisted, to “compete for resources” (rather than to directly gain sustenance, which I believe is perfectly natural and excusable) as April put it, despite their branding as barbaric hordes and merciless slaughterers of innocents. Army ants, the many kinds of which are found almost worldwide, are integral parts of the rainforest ecosystem, actually preventing “peaceful” herbivorous insects from—shall I quote here?—“decimating everything in their path”. Only someone with a very dim concept of ecology and non-human behavior would call army ants sadistic conquerors.
    Furthermore, referring to some kinds of ants (such as Harpagoxenus and Polyergus) as “slave makers” is another sad example of ants being anthropomorphized by uninformed laymen. Calling them “adopters” or “foster families” would be more accurate. While it is true that ants that practice dulosis (a behavior in ants that humans often inaccurately term as “slavery”) brutally kill other ants to capture those ant’s pupae, those ants that emerge from the said pupae are brought up as members of their foster colony and are never discriminated from their “enslavers,” as far as myrmecologists can tell. I define slavery as being the capture of a member of your own species and the coercion of that individual to do work that you consider too dirty, dangerous, or dull (DDD, if I may utilize an acronym originally used in robotics) for you to do yourself: on the other hand, while the notorious dulotic myrmicine ant Strongylognathus emeryi, for instance, makes those ants that it has “enslaved” do work that it never does (namely, feeding other S. emeryi members of the colony), this is not because it is unwilling to do this work itself but because it is unable to, because the gigantic mandibles it possesses are (get this!) too massive and clumsy to do anything but slice apart other ants. Dulotic ants never enslave their equals—the closest human analogy to dulosis would be a human family stealing a baby monkey from its parents, bringing it up as one of their own, and training it to answer the telephone because the humans did not have an answering machine and were usually too busy to answer it themselves.

  6. Zach, thank you for the fascinating and thoughtful comment. I for one will think twice before I use the phrase slave-makers to describe ants. Good stuff.

  7. What they look like:
    Army ants grow to be about 1 inch. They can be dark brown or black. They have very large and strong pincerlike jaws. The males have wings.
    What they eat:
    Anything they can subdue in their path. They eat other insect, snakes and small animals such as baby birds. The whole colony will overtake the smaller animal and eat it. The ants send out special scouts to look for food. When they find it the go and tell the others. They leave a special smell that the others can follow.
    Where they live:
    Army ants like warm tropical temperatures. They can be found in the lowland forests of South and Central American and the some of the southern points of North American. India and Malaysia has a similar species.
    How they breed:
    They lay eggs. They can lay up to 120,000 a one time. The LARVAL STAGE takes 23 – 33 days and the PUPATION STAGE 10-15 days.
    Special Characteristics:
    Army Ants live in huge colonies. There are worker ants (most of the ants are workers), soldiers and a queen. The ants travel in stages. When they are migrating they go on the march and stop to rest at night. One neat trick the ants do is to make a nest with their bodies so the queen and the babies can rest. When they are not marching they are in the STATIONARY phase. This is when they make a nest and the queen lays her eggs.
    Army ants can march 65 feet in an hour.
    The queen only mates once in her life.
    Soldier ants march on the side and protect the other ants.
    1. Add the Army Ant to your animal notebook. It will go under ARTHROPODS – INSECTS. You can make another divider if you like for the order HYMENOPTERA.
    2. Print out this worksheet. Mark where the army ants live.
    3. Get an ant farm and watch how other ants live. The army ants feed and take care of their queen the same way.
    4. Draw an ant and label the body parts. This chart will help you.

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