Science: The ultimate sacrifice…as a routine

If you were an ant, what would you do when you don’t want your nest-entrance to be found?

Many ants answer this question by trying to block off their nest-entrance at night, presumably in order to prevent predators and parasites from ever finding their nest.

However, when you’re closing off a hole in the ground with sand…you’ll have to stop at some point, because otherwise the opening won’t be big enough for you to pass through anymore. Furthermore, you can’t take extra steps to camouflage the entrance if you do it from the inside.

Forelius breviscapus at their nest entrance. Picture by Alex Wild (www.alexanderwild.com)

Forelius breviscapus at their nest entrance. Picture by Alex Wild (www.alexanderwild.com)

In 2008, Adam Tofilski and colleagues found ants that solve this problem in a remarkable way. Every night, when closing off the nest-entrance, one to eight workers of the Brazilian ant Forelius pusillus stay outside in order to close off the nest completely. At the end of the process, they show a peculiar behaviour we might recognise from dogs: they turn around, and start to kick sand all over it, in order to camouflage it completely.

Now comes the sad part…the ants that stay outside don’t survive the night. The researchers even caught on video how they can be blown away by the wind at night. Even sadder…this happens every night.

Of course, the number of ants in a big colony has been estimated to be up to 100.000, so eight workers per night might be a very small price to pay for such a big advantage of having your nest entrance hidden.

Conclusion: Every night, some ants heroically sacrifice their lives in order to prevent their colony from being found by others.

Source:
Tofilski et al. (2008). Preemptive defensive self-sacrifice by ant workers. The American Naturalist 172(5), E239-E243

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