Cannibal ant colony discovered in abandoned nuclear bunker in Poland

A colony of ants has apparently survived for years after falling into a post-Soviet nuclear bunker in Poland and has stayed alive by strategically cannibalising the fallen members of their own kind, researchers believe.

The ants were discovered in 2013 thanks to a yearly effort to count hibernating bats in the same bunker. But the colony the researchers found was unusual, as it was composed entirely of worker ants and had no obvious available food source.

Now, scientists from the Museum and Institute of Zoology at the Polish Academy of Sciences, in Warsaw, have deduced that the thriving community was sustained by cannibalism, and that the ants in the bunker were an accidental offshoot of a larger colony living at ground level near small ventilation pipes leading into the subterranean bunker.

When they were first found, the scientists estimated the presence of close to a million individual ants.

The insects ended up in this situation as a result of large numbers accidentally falling down the ventilation pipe and being unable to climb back up to their nest.

Several years later, the ants in the bunker still appeared to be thriving, prompting an investigation into how this was possible.

In a newly published paper, Professor Wojciech Czechowski and Dr István Maák said their investigations revealed the wood ants were consuming the dead bodies of their fallen comrades that were accumulating on the bunker floor. In nature, a similar behaviour occurs frequently during spring, when protein food is scarce.

Neighbouring colonies engage in so-called “ant wars”, which set territorial boundaries and also provide food in the form of the fresh corpses.

Recent research has also shown that corpse consumption among wood ants is more common than previously thought, and that even the corpses of their nest-mates can serve as an important food source – and not only in periods of food shortage.

“Here we show that the ‘colony’ in the bunker survived and grew thanks to an influx of workers from the source nest above the bunker and mass consumption of corpses of the imprisoned nest-mates,” the authors said.

In 2016, the scientists experimented with creating a bridge for the ants to allow them to return to the original colony. At first they allowed a hundred individuals to regain access to the nest, where they saw they were accepted as belonging to the larger, original colony.

After this success they made the bridge permanent, and more recent visits to the bunker have revealed very small numbers of ants still living down there, with the vast majority believed to have returned to the original nest.

The research is published in the Journal of Hymenoptera Research.