Since 2012, as part of a campaign to count overwintering bats, scientists have examined an old nuclear weapons bunker in Poland. In the summer of 2013, they made another discovery: a population of wood ants (Formica polyctena) was living down there in conditions that made it extremely difficult to survive.
The ants had little or no food sources, and they had no access to the outside world. On top of that, the temperature inside the bunker was very low — just 10 °C (50 °F). These conditions made it seemingly impossible to produce offspring, and the scientists were unable to find ant larvae, pupae, queens, or males.
Yet, despite these conditions, each time the scientists returned to the bunker, the colony’s population seemed to grow. But how?
It turned out that wood ants had established a colony in the forest above the bunker, and each year a number of ants falls down a vertical ventilation pipe into the bunker, from which they cannot return. Somehow, these workers from the above-ground mother colony are able to adapt to the underground conditions and carry on. This unique population is described in the Journal of Hymenoptera Research.
The scientists deducted that the constant influx of newly fallen ants was enough to not only maintain the population, but to grow it. In fact, the mortality rate in the bunker is quite high, but the regular newcomers turn out to be overcompensating for the dead ants.
“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 authors wrote.
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