Ants have been in the press a lot lately.
A few weeks ago the web (or the relevant slice of it) was buzzing with the discovery that ants deliberately inoculate themselves against infection by the deadly Metarhizium fungus – making contact with infected nestmates to dilute the fungus and immunize themselves. This is really, really cool (similar behaviour was seen a few years ago too).
But another paper showed that workers of a different species of ant infected with the very same fungus will actually quarantine themselves to protect the rest of the colony. They do this by radically altering their behaviour, becoming unsociable and aggressive. Cue the Hollywood dramatic imagery! Stay alive! Save yourselves!
How do we make sense of these two findings? It will now be really interesting to see how these behaviours interact – at what point does it stop being a good idea to spread the infection around, and instead become an aggressive loner? Of course these behaviours may also be confined to the ants in which they were found (Lasius and Camponotus, respectively).
But this barely scratches the surface of how jaw-droppingly, staggeringly amazing ant behaviour can be.
I can’t resist it: here are my 5 currently favourite factoids about ants. It is sometimes an effort to remember that ants are a matter of millimetres long…
1. Arable and dairy farming. It is well known that some ants “milk” aphids for their honeydew – this 2007 paper shows they control their aphids’ movements with chemical tranquilisers in their footprints! Leafcutter ants also maintain large scale “arable” farms of fungi (of different cultivars) within their enormous nests (did you know that snails do this too?!). Less well known is that the ants also maintain active cultures of bacteria on their cuticles whose secretions protect the ants against pathogens in the fungus.
2. Teaching (or teaching-like behaviour). Ants that know where food is will transfer this information to naive nestmates using a behaviour called “tandem running”, very similar to guiding a blindfolded friend – or how honeyguides lead humans to bees’ nests. It has been argued that this actually formally constitutes “teaching”, but see this review for a critique. For a cast-iron (and stupendously cool) example of real animal teaching, see Alex Thornton’s work on teaching in wild meerkats.
3. Surfing, rafting and swimming. Ants that live near the sea have an adaptation to help them to survive when inundated by waves: they surf! Even more amazingly, a recent paper showed that a whole colony of fire ants dropped into water will quickly arrange themselves into a floating raft – although some are under water, each has a bubble through which it can breathe and the whole colony survives. This could well save the nest in a flood situation. One species has even evolved the ability to swim, which allows it to steal the prey caught by pitcher plants in the Bornean rainforest.
4. Paragliding (or base jumping..). Ants that live in very tall trees in the rainforest can control the direction of their fall if they fall out of the tree – and guide themselves back to the trunk instead of falling up to 100ft onto the forest floor. There’s some great (and funny!) video of this happening at canopyants.com.
5. Computing! Ants can solve computationally difficult optimization problems. Chris Reid and colleagues recently showed that, by teamwork, ants make easy work of computing problems such as the Towers of Hanoi – a simpler version of the kinds of problems telecommunications companies have to tackle every day. This “swarm intelligence” is increasingly becoming a model for computing networks.
These are just some of the ones that wow me every time I think about them, but ant behaviour is a vast, rich and exciting Aladdin’s cave for anyone interested in reading further. I really envy those who work on ants: one day I will get there, hopefully!