Wojciech Stephan

Wojciech Stephan

Wojciech Stephan

Wojciech Stephan

Wojciech Stephan

Wojciech Stephan

Wojciech Stephan

Wojciech Stephan

For the past several years, a group of researchers has been observing a seemingly impossible wood ant colony living in an abandoned nuclear weapons bunker in Templewo, Poland, near the German border. Completely isolated from the outside world, these members of the species Formica polyctena have created an ant society unlike anything we've seen before.

The Soviets built the bunker during the Cold War to store nuclear weapons, sinking it below ground and planting trees on top as camouflage. Eventually a massive colony of wood ants took up residence in the soil over the bunker. There was just one problem: the ants built their nest directly over a vertical ventilation pipe. When the metal covering on the pipe finally rusted away, it left a dangerous, open hole. Every year when the nest expands, thousands of worker ants fall down the pipe and cannot climb back out. The survivors have nevertheless carried on for years underground, building a nest from soil and maintaining it in typical wood ant fashion. Except, of course, that this situation is far from normal.

Polish Academy of Sciences zoologist Wojciech Czechowski and his colleagues discovered the nest after a group of other zoologists found that bats were living in the bunker. Though it was technically not legal to go inside, the bat researchers figured out a way to squeeze into the small, confined space and observe the animals inside. Czechowski's team followed suit when they heard that the place was swarming with ants. What they found, over two seasons of observation, was a group of almost a million worker ants whose lives are so strange that they hesitate to call them a "colony" in the observations they just published in The Journal of Hymenoptera. Because conditions in the bunker are so harsh, constantly cold, and mostly barren, the ants seem to live in a state of near-starvation. They produce no queens, no males, and no offspring. The massive group tending the nest is entirely composed of non-reproductive female workers, supplemented every year by a new rain of unfortunate ants falling down the ventilation shaft.

Like most ant species, wood ants are tidy animals who remove waste from their colony. In the case of the bunker ants, most of this waste is composed of dead bodies. The researchers speculate that mortality in the "colony" is likely much higher than under normal circumstances. "Flat parts of the earthen mound [of the nest] and the floor of the adjacent spaces ... were carpeted with bodies of dead ants," write Czechowski and colleagues. This "ant cemetery" was a few centimeters thick in places, and "one cubic decimeter sample contained [roughly] 8,000 corpses," which led the researchers to suggest that there were likely 2 million dead ants piled around the nest mound. The sheer numbers of dead bodies suggest that this orphaned wood ant nest has been active for many years.

The ant graveyard is also host to a tiny ecosystem, where mites and a few other invertebrates feed on the bodies of the dead wood ants. The question is, what are the wood ants eating? It's possible they have figured out how to eat the creatures who feast in their cemeteries, essentially making them cannibals at one remove. But Czechowski and his team dismiss this as unlikely. It's also possible that there are nutrients growing in the bat guano from the ants' only living neighbors in the bunker. But in their years of observation, the scientists still haven't figured out for certain what the ants' source of food is.

Wood ants are known for surviving in harsh conditions, and they have been found on remote islands as well as living in small, closed boxes. And it's not impossible that this underworld colony could bloom into something more. In a previous experiment, Czechowski showed that orphaned wood ant colonies will adopt queens from related species. So if a queen ant fell down the pipe, she might join this colony and start reproducing. Unfortunately, however, without a steady food supply the ants probably wouldn't have enough energy to raise a new generation and keep the nest warm for them. So the only way this nest carries on is by waiting for a new rain of ants from the free colony above ground.

The paper's conclusion reads like a dystopian science fiction scene from the 1970s:

The wood-ant ‘colony’ described here – although superficially looking like a functioning colony with workers teeming on the surface of the mound – is rather an example of survival of a large amount of workers trapped within a hostile environment in total darkness, with constantly low temperatures and no ample supply of food. The continued survival of the ‘colony’ through the years is dependent on new workers falling in through the ventilation pipe. The supplement of workers more than compensates for the mortality rate of workers such that through the years the bunker workforce has grown to the level of big, mature natural colonies.

Life in an abandoned nuclear weapons bunker is nightmarish, even for the humble ant. It appears that the legacy of the Soviet occupation of Poland doesn't just haunt the country's human population. It has affected the social structures of insects too.

Journal of Hymenoptera Research, 2016. DOI: 10.3897/jhr.51.9096

Listing image by Wojciech Stephan