Researchers tiptoe through the creepy shell of a Soviet bunker, paint peeling from its walls and tiles cracked beneath their feet. One corner of the empty space buzzes with life, though; a colony of ants, probably numbering more than a million strong, have built a mound in the underground outlet. How the insects have survived, though, is perplexing – until scientists realize the horrifying truth.
At first, the underground ant colony appeared normal. They had built a mound, as they would have done on the surface, but the experts knew these ants couldn’t be normal per se. They simply couldn’t engage in their usual social behaviors in the underground, lightless bunker where they had ended up.
That’s not to say that wood ants haven’t been found in caves before. Most of the time, though, they dwell near the entrance or in spots where they still get some light. Plus, access to the outside world would allow them to get their sustenance from the trees, as they have evolved to do.
But the wood ants in this particular cave-like space had no access to the outside, let alone to any light. Experts quickly realized how they had ended up in their bunker-based colony, but it took a little more digging to find out how they had managed to thrive. Peering through a microscope back in their lab, they saw things close-up – and discovered the startling truth about these desperate insects.
One doesn’t just walk into a former Soviet bunker – at least, not the one hidden near Międzyrzecz, a town on Poland’s western flank. For one thing, the former Communist regime tried to hide this particular nuclear installation behind thick foliage. Pine and spruce trees tower over the entrance, obscuring it from view as planned.
During its heyday – which spanned from the 1960s until 1992 – the bunker was called Special Object 3003 Templewo. At one time, it needed tree cover to hide its location, as the Soviets built and stored weapons there, including nuclear ones. What’s more, they didn’t just use one underground container for such activity – multiple such spaces hide beneath the surface in the same forest.
But these days Special Object 3003 doesn’t just pique the interest of those concerned with modern political history, because in the years since it was abandoned by humans it has served as an animal habitat, too. For instance, bats now flap in and out of the one-time Soviet bunker, where internal conditions remain close to a comparatively temperate 44F year-round. And, on top of an external air vent, a colony of wood ants have built a mound.
It makes sense that wood ants would build such a nest here; as their name implies, they generally reside in tree-covered areas. They build massive mounds in the midst of their chosen habitat so they can defend themselves and their source of food outside of the nest. What you see above ground is just part of their construction: typically, the underground portion is just as large as what juts above the surface.
Interestingly, though, wood ants don’t rely on the trees around them for food – at least, not directly. Instead, they get 90 percent of their food from honeydew naturally produced by tree-sap-eating aphids.These bugs excrete any extra sugar their bodies don’t need, which the wood ants milk and eat themselves.
The relationship between wood ants and aphids is mutually beneficial to both insects. The former, of course, derives sustenance from the latter. In exchange for the aphids’ so-called honeydew, the wood ants protect the bugs and even shuttle them around so they can nosh on better parts of the tree.
Clearly, wood ants work hard to get the sugary food they need. They have been seen climbing trees nearly 100 feet tall to reach honeydew-making aphids at the top. All of this serves the mound-based community, as the collector ants return to the nest and regurgitate the sweet stuff for workers and the queen ant.
So, the wood ant mound situated outside of the Soviet bunker – and amid its camouflaging evergreen trees – made sense. Colony members had access to trees and the aphids living amid the boughs. But in 2013 experts uncovered another ant colony in the area, the continued survival of which confounded them.
Experts hadn’t originally entered the bunker in search of ants, either. A 2013 study, helmed by Wojciech Czechowski, pointed out Special Object 3003’s attractiveness to the local bat community. And, because of the winged creatures’ presence within the bunker, the study author found that animal lovers had found ways to sneak into the space to see them. However, their unsanctioned explorations had nonetheless unwittingly paved the way for further research to take place within.
Bats colonizing within the Soviet bunker undoubtedly made the underground facility all the more creepy, too. Even without the flying mammals, though, it’s not a welcoming piece of history. Paint strips curl and peel from the walls – which measure in at three feet thick – and a one-time terracotta floor has transformed into a layer of rubble.
Traipsing through Special Object 3003, one would happen upon a closet-sized room labeled only with the number 12. A ventilation pipe opens within it – the endpoint of the one upon which the wood ant community has built their mound. The location of the insect-based construction hints at what you’d find underground in Room 12.
In the small space existed a second ant colony, and, since at least 2013, it sustained a stunning one-million-strong population. This underground faction operated much differently than its overhead counterpart, experts found. Polish Academy of Sciences zoologist István Maák explained the colony’s setup to online magazine and travel firm Atlas Obscura in November 2019.
Specifically, Maák said that the underground mound didn’t have the typical wood ant hierarchy. He explained, “They had no larvae and no queen. But still they survived and kept their organization without any goal of life.” Without larvae, the ants didn’t reproduce – but, somehow, they kept their population numbers steady for years.
Experts found that the steady population numbers could be explained by the setup of room 12 – and its ventilation pipe, specifically. Atop the pipe stood the outdoor wood ant mound, which created a huge danger to the insects in that colony. Stepping in the wrong direction could (and regularly did) send some of its members plummeting down the chute and into the bunker.
Once wood ants fell through the ventilation pipe and into the bunker, they had no way of escaping, nor did they have access to their normal outdoor resources. So, the unlucky population of underground ants had to come up with ways to survive – and experts decided to figure out how they made their lightless, aphid-free habitat work for them.
The results of the study – helmed by Wojciech Czechowski – appeared in the Journal of Hymenoptera Research in August 2016. The researchers gave a detailed description of the underground ants’ living situation, including their low, wide mound. It had several entrance and exit holes, through which the trapped insects easily traversed.
But that was where the normality of the ants’ living situation ended. The researchers found the rest of the space to be an eerie landscape – and not just because it was buried deep underground. Surrounding the mound and in other parts of the bunker, they found a carpet-like covering made up of dead ant corpses.
In some places, the experts recounted, the bodies stacked centimeters high atop the bunker’s one-time terracotta floor. They found a few other dead insects, as well. Experts theorized that they had come from the overhead mound, too. Wood ants can be predatory, so the outdoor colony might’ve caught these insects, then accidentally dropped their bodies down the chute.
At the end of this first study, the researchers found that the bunker simply did not have enough food available to sustain the massive population of ants living there. They pointed to previous populations of other social insects left to live in environments such as caves: other ants had been unable to build even small colonies in similar settings.
So, how did the Soviet bunker-based wood ant colony make it for years with such a large population? A second study published in the Journal of Hymenoptera in October 2019 proposed a viable theory as to how honeydew-eating bugs had survived underground. And the findings were disturbing, to say the least.
The research team found their answer by studying the bodies of the dead ants. In a lab, they slid more than 150 ant bodies which they had collected beneath a microscope so that they could magnify the corpses by ten times. With such a close-up view, they could see that many of the deceased insects had holes in them, mostly in their abdomens.
The holes weren’t part of the decomposition process, though. It appeared that the ant bodies had instead been bitten. And evidence that the dead bugs had been munched upon post-mortem revealed that their living nestmates had apparently resorted to cannibalism in order to survive their harsh living conditions.
The researchers didn’t have much previous experience of social-insect cannibalism with which to compare the bunker-based activity they had uncovered. However, they did know that wood ants would eat bugs from other colonies in the wake of a territorial combat. Specifically, they’d drag enemy bodies into their mounds to feed their babies.
But further research in the bunker and beyond has shown that cannibalism often helps wood ants to survive the occasional food shortage. In the case of the Soviet storage-bound ants, the experts could only deduce they had done the same. There was no evidence that other insects lived within the space that had the capability of consuming so many dead ants.
So, the bunker ants maintained their population size as their overhead brethren fell through the ventilation pipe that opened into room 12. And, once they landed in the underground space, the ants had no choice but to partake in cannibalism. Otherwise, they couldn’t have survived in the harsh, human-made landscape.
To the researchers, this underground ant colony served as an incredible display of insect resilience and adaptability. However, as Maák told Atlas Obscura, those who read the study weren’t as keen to see the situation play out. He said, “[Study author] professor Czechowski got many letters saying how cruel it was to keep the ants down there.”
Specifically, Maák said, “People kept asking why we did not set them free.” For the experts on this study and any other wildlife-centric study, the answer to that question isn’t an easy one to provide. In most cases, they choose to leave animals as they find them – even if intervention seems the humane choice.
Maák admitted that he grappled with whether or not the bunker-based research team should do anything. However, some of his colleagues presented a valid point. The ants wouldn’t have fallen underground if it weren’t for the humans who had built an underground bunker in the middle of their habitat.
On top of that, the researchers had done all they could to learn about the ants’ underground survival. If they stepped in to reunite both halves of the colony, they could continue studying the insects. Specifically, they could see how the ants managed their new duplex-style living situation. These ideas helped seal the deal: the researchers would help the bunker bugs escape.
Before they could do anything, though, the researchers had to make sure the wood ants would still recognize each other as nestmates. Their species was, of course, territorial, so if new ants approached the mound, it could end in carnage – and, perhaps, total destruction – on both sides. So, Maák came up with a plan.
Maák unearthed a test group of approximately 100 underground ants. He placed them at the base of their mother nest and waited to see if they’d be welcomed. Not only did the insects move toward the mound without issue, but they filed right into worker-ant life within their original nest.
With a successful reunion on the books, Maák had to come up with a more permanent solution to rejoin both halves of the colony than carting the rest of ants from the bunker. He came up with a clever idea that he called an “experimental boardwalk.” The wooden plank connected the main nest with its underground faction and allowed any ants that fell to climb up and rejoin the ranks.
After the team installed their makeshift insect bridge, they watched as the wood ants approached it. They didn’t climb it right away, though; they simply inspected the new addition to their habitat. With that, the research team left the creatures to their devices and returned a year later to see if the bugs had used their human-made escape route.
The researchers found the underground mound had been almost entirely deserted by the colony. A few lingering insects remained, and most hovered at the base of the boardwalk. This led the experts to believe that the one-million-strong population had climbed up to rejoin their original nest – and any fallen comrades had likely done the same.
In the end, the underground ants taught the researchers several lessons about how they could thrive, even without producing offspring. They had to rely on unsavory means for doing so, but the bodies of their nestmates provided enough food to keep them going for years – until their boardwalk escape appeared.
For Maák, though, the most impressive element of the entire episode was the resilience and survival instincts of these tiny creatures. The underground mound had thrived without light or traditional food sources, after all. He told Atlas Obscura, “They couldn’t predict that we would come in to save them, but they were still surviving and fighting for something. And that is exciting.”