Study Tracking Individual Ants Reveals They Change Jobs with Age

By Wesley Fenlon

Old and grizzled? Go get the youngsters some food--you should be able to handle the tough outside world.

When you're young, your first job is to take care of other people and keep them fed. As you grow older, you feel like expanding your horizons. You roam, and start taking cleaning jobs wherever you can find them. Finally, when you're older and wiser to the ways of the world, you venture outside the safety of your society to find food and bring it back to a colony that relies on your survival instincts and resourcefulness in the outside world. Also, you're an ant.

Photo credit: Alessandro Crespi

Nature published about an interesting ant study on Thursday that highlights the findings of a Swiss research paper published in science. For 41 days, the researchers tracked every single ant in six different carpenter ant colonies raised in their lab. Cameras positioned above the flat colonies captured the ants' every movements. More importantly, each ant was tagged with a paper barcode, allowing a computer to follow individual ants through their lives. After 41 days of noting each ant's position twice every second, the researchers amassed more than 2.4 billion readings.

Now for the really interesting part:

"The researchers found that around 40% of the workers were nurses, which almost always stayed with the queen and her brood. Another 30% were foragers, which gathered most of the colony’s food and were found near the entrance to the nest. The rest were cleaners, and these were more likely to visit the colony’s rubbish heaps.

The workers move between jobs as they get older — nurses are generally younger than cleaners, which are younger than foragers. Honeybees go through similar transitions from young nurses to older foragers, but this study provides the clearest evidence yet that ants do the same."

The study helped them deduce that foragers and nurses rarely interacted, likely to isolate the queen from any diseases brought in from the outside. But the study also raised questions, like why the ants change jobs. And sometimes they don't--sometimes they'll stay nurses, or become foragers at young ages. It's also possible that the study's laboratory setting, where there was no danger to foragers leaving the colony, affected behavior.

Still, ant behavior? Really complex! See also: How ants affect to being pulled around by magnets.