In an abandoned nuclear bunker in western Poland, hundreds of thousands of worker ants that fell in and were cut off from the main colony survived for years by eating the bodies of their dead.
When researchers visited the bunker in 2016, they described a community of nearly a million worker ants of the species Formica polyctena, or carpenter ants. The main colony swarmed above ground on a knoll atop the bunker’s ventilation pipe; over the years, a steady stream of unfortunate ants fell through the pipe and into the bunker. Since the pipe opened into the room from the ceiling, once they landed on the floor, the ants were unable to climb out.
There was nothing for the ants to eat in the pitch-dark bunker; in 2016, the scientists hypothesized that the insects survived by cannibalizing their dead comrades. Recently, the researchers returned to the bunker to continue their investigation of the trapped ants, looking for evidence that the insects ate the corpses of their nestmates.
Related: Soviets Hide Nuclear Bunkers in Poland’s Forests (Photos) (opens in new tab)
The bunker, once part of a nuclear base, is located near the German border and was used for storage by the Soviet army nuclear weapons from the late 1960s to 1992, the researchers reported in 2016.
“During an inspection in July 2015, we measured the size of the bunker ‘population’ of Formica polyctena to be at least several hundred thousand workers, maybe close to a million,” the scientists wrote online Nov Journal of Hymenoptera Research. As thousands of ants scurried across the bunker floor and walls, they were unable to walk across the ceiling where the pipe opening provided the only exit from their stone prison.
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There were no ant cocoons, larvae, or queens in the bunker, so the queenless “colony” wasn’t breeding. On the contrary, it kept growing because ants constantly fell through the open pipe when the main colony was active, the researchers reported.
Worker ants wouldn’t normally branch out and form a new colony without a queen, but the ants trapped in the bunker “had no choice,” the scientists wrote. “They were just surviving and continuing their social duties under the conditions of the extreme environment.”
Eat or be eaten
For the new study, the scientists collected more than 150 dead ants from “cemeteries” — piles of bodies on the floor and near the walls surrounding the bunker’s main ant mound. Bodies with gnawing marks on their stomachs were believed to have been cannibalized; sure enough, a “vast majority” – 93% – of the corpses showed signs of being eaten.
The ants’ solution was a grim solution, but cannibalism is not uncommon in this species. Carpenter ants are known for waging “ant wars” – fierce battles with other ant species which, according to the study, are typically fought in early spring, when food is scarce. As corpses of fallen soldiers pile up, workers drag the bodies to their nests to feed developing young. In fact, “nestmates’ corpses can serve as an important food source, not just during periods of food shortage,” the scientists wrote.
Inside the bunker, the corpses served as an endless buffet, allowing the ants to survive in a location where they would otherwise have starved, the researchers said.
As horrific as those conditions were for the bunker ants, their story has a happy ending (at least, for the ants that weren’t eaten). The study authors also wondered if they could help the trapped ants find their way home, and in 2016 they installed a vertical “boardwalk” — a wooden beam that extends from the floor to the pipe’s entrance.
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When the scientists returned to the bunker in 2017, they found that most of the ants had taken advantage of the new escape route. The bunker area previously teeming with hundreds of thousands of ants was “almost deserted”, presumably with all the wayward ants finally reunited with their colony above ground, according to the study.
Originally published on Live Science.