Did LiveLeak Just Leak An Unknown Ant Behavior?

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Those corners of the internet prone to viral outbreaks are abuzz today with an intriguing ant video:

Is it real? Yes.

The quality isn’t great, but the clip appears to show an Asian Leptogenys daisy-chaining their bodies in parallel lines to haul away a large millipede. I have spent the morning searching the technical literature for mention of this unusual behavior, and am coming up empty. Some Leptogenys species, including L. diminuta, L. nitida, and L. processionalis, are known to forage in groups and transport prey “cooperatively” (source, source). What is meant by “cooperative” is often vague. (For more, see this excellent recent review of cooperative transport by Helen McCreery).  Yet I didn’t find any explicit description of workers linking up, mandible to abdomen, to pull together.

Is ponerine daisy-chaining an unknown behavior? Possibly. It is also possible my search skills aren’t up to the task. If you know of a description of it, please drop a note in the comments. I am not the only one interested, either:

couzin

I did, however, happen across a higher quality video from a Cambodian beekeeper:

I presume the swelling music helps motivate the ants to pull harder. But, I digress.

Steve Shattuck took a photograph recently in Borneo capturing a variation on this behavior, with workers forming a chain by biting the legs of a preceding ant.

Leptogenys1

Again, I don’t think the behavior has been formally described beyond this smattering of visual media.

Regardless of documentation, daisy chaining raises some definitely unanswered questions and will make a fine Ph.D. thesis for some lucky student. How do ants organize themselves in chains? What cues do they use? How do they know to let go? Is chaining employed only for particular sizes or species of prey? How does the behavior effect overall foraging efficiency? What are the evolutionary precursors to chaining? And, do these ants have any other tricks up their coxae?

 ***Update 8/30/2014 – 

In the comments, Roberto Keller suggested that the eminent ponerophile Christian Peeters might know something. And indeed, Christian emails in with the following:

I observed this fascinating behaviour in Cambodia 4 years ago. Stéphane De Greef was with me and some of his photos are attached.

The behaviour was very stereotyped: mandibles grab preceding ant’s gaster (between first and second segment).

Seiki Yamane identified it as Leptogenys sp. 47, closely related to L. chalybaea described from Borneo by Emery (but stronger sculpture especially on gastral tergites).

The millipedes were 130mm long, identified as order Spirostreptida (Diplopoda). Ant is 16mm long.

Back then I reviewed the literature and found no other record of chain behaviour in Ponerinae. No record of millipede predation in Leptogenys.  Specialized hunting on millipedes is restricted to Thaumatomyrmex, Probolomyrmex and Gnamptogenys, but these are solitary hunters on a very different kind of millipedes (polyxenids).

I started writing a ms on this behaviour (formation of chains in ants through a self-assembling behaviour) but sadly I have not been able to get further observations. It seems to happen at certain times of the year only.

By an amazing coincidence, two days ago I finished fieldwork in northern Thailand and came across the same Leptogenys species. There were cleaned out ring segments of big millipedes outside entrances. Unfortunately I did not observe any raids.

Image by Stéphane De Greef, used with permission.
Image by Stéphane De Greef, used with permission.

postscript: The virality of the video also illustrates both the good and the bad about the internet. The good, of course, is that this fascinating ant behavior found its way in front of scientists who otherwise might not have seen it. On the other hand, the viral nature of the video means that actual person who filmed it is drowned out among the hundreds of uncredited, unsourced copies. Securing the information about where and when the video was taken, and verifying the species, is going to be difficult. This is one reason why crediting sources online is important. Lose the credit, lose the data.

30 thoughts on “Did LiveLeak Just Leak An Unknown Ant Behavior?”

  1. Christian Peeters showed me photos of these chains some years ago. Ask him, he will know if there’s anything published or on the making.

  2. In deed a fascinating behaviour. B. Hölldobler (1983) mentioned that Oecophylla smaragdina sometimes forme short “pulling chains” to retrieve preys. (But nothing like those Leptogenys!!)

    [Hölldobler B. Territorial behavior in the green tree ant (Oecophylla
    smaragdina). Biotropica 15 (1983): 241-250.]

          1. I’m a little late to the comment party but I’d love to go! No dragging-by-chain required, though that would certainly be more fun!

  3. In his dissertation Volker Witte (2001) studied the coordination of raiding and emigration in several Leptogenys species. He observed chains of up to 5 L. distinguenda workers, biting with their mandibles into a nestmate during transport of large prey (p.44). Information on raiding and emigration dynamics as well as their coordination is given in Witte & Maschwitz 2000 and 2002, respectively. Unfortunately, the “chaining” behavior is not described in detail. But Volker may be able to provide unpublished notes.

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  5. Another area to workout is the ant body itself. There is one photo where the ant is biting the rear leg of the ant in front of it. If you chain 5 or 6 ants together why don’t the pull the legs off completely. Secondly, How strong is the ants body. When they attach jaw to abdomen in that chain then each ant body in the chain has to have a fairly high proportion of the millipedes weight as a force. Can an ant body support a millipede or even half a millipede. The 16MM and vs the 130 mm milli is one thing but what about weight?

    1. Bert Hoelldobler (et al.) did some centrifuge experiments that were published a while ago that answer some of this. An OSU MechE lab (Blaine Lily? I’ll repost after I find it again) has done some extensions of that sense then.

    2. Mark — This is a follow up to the previous comment. The tensile strength of an ant body has long been of interest for a number of different species, with collective transport, self assembly, and even individual prey capture as drivers. Check out this article for an example:

      Wojtusiak, J., 1995. Capture and retrieval of very large prey by workers of the African weaver ant. Trop. Zool. 8(2), 309–318.

      There, you can find an image of a single weaver ant supporting a baby bird over the edge of a table. Despite the relief from the friction on the table, that’s a significant tension to be supported by the neck and lots of compression on the legs.

      Ingenious ways of measuring the tensile strength have been used, as in this article whose title gives away most the the details:

      Federle, W., Rohrseitz, K., Hölldobler, B., 2000. Attachment forces of ants measured with a centrifuge: better ‘waxrunners’ have a poorer attachment to a smooth surface. J. Exp. Biol. 203, 505–512.

      Since then, the empirical, computational, and analytical methods have gotten much better, as in:

      Ngyuen, V., Lilly, B., Castro, C., 2014. The exoskeletal structure and tensile loading behavior of an ant neck joint. J. Biomechanics 47, 497–504.

      But you have to keep in mind that for a daisy chain, the ants in the chain might not have synchronized pulling. So the instantaneous force down a chain might oscillate and never be a simple multiple of the individual force of a single ant. It’s possible that the reason you see multiple chains in parallel is because of this temporal imbalance. Just like 3-phase electrical power, having three chains with oscillating force may combine so that at any one time, there is roughly a constant force from the ensemble.

      Also keep in mind that three parallel chains will divide the total pulling force along them. So having parallel chains reduces the tensile load on each individual chain.

      So it may be all about pulling uniformly as an ensemble and then reducing the tensile load — both require parallel chains. Again, I think the 3-phase analogy to AC power may be useful here.

  6. TedPavlic thankyou for the reply. The bird deal is amazing.
    I am a novice in the world of ants, I used to destroy any mound I encountered BUT Alex made me look at these creatures completely different. Now, I look down in amazement. With a friend, hiking in Arches National Park we got to the top of a sandstone ridge and there was beautiful scenery all around, I was looking at the ants, wondering what they ate up here as there was almost no vegetation and sparse soil but I identified at least three types of ants roaming the rock. My hiking partner thought I was nuts not taking pics of the scenery and following ants across the rock. It’s all because of you guys and gals. Keep up the good work and thanks for entertaining/informing/educating us inquiring minds.
    I guess it is no big thing to the ants if one breaks in half due to tensile overload, he just gets replaced and they continue on, it does raise huge questions about “how they know to cooperate” Thanks again Ted

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  8. I agree that it’s difficult to tell whose video it is! While looking for the source, I found this photo of ant chaining:

    http://tanzalongs.wordpress.com/2014/05/15/weekly-a-photo-challenge-on-the-move-7-on-a-different-scale/

    “Another submission to this weeks Photo Challenge from my trek through Yok Don last summer in Vietnam.”
    “These ants had captured a centipede and were dragging it away. I love the way they joined to form ‘ropes’ which heaved the bug along.”

    Which is at least by the person who took the photo!
    bena

  9. I have one more idea – maybe volatile compounds released by millipede disturb the sens of smell of ants. Only the farthest ones in chain are able to find their way home. Have anyone found any other prey being pulled this way?

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