Ants trapped for years in an old bunker; survival by cannibalism and eventual escape

Abstract

Successful evacuation of a peculiar ‘colony’ of the wood ant Formica polyctena Först., for years trapped within an old bunker previously used for storing nuclear weapons (see Czechowski et al. 2016), is reported. Using an experimentally installed boardwalk, the imprisoned ants managed to get through the ventilation pipe to their maternal nest on the top of the bunker. In our previous report, we left open the question of how the ‘colony’ could survive seemingly without food. 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 nestmates.

Behaviours indicating cannibalistic necrophagy in ants are modulated by the perception of pathogen infection level

“…We assumed this based on the weight loss of the paint-marked corpses and the presence of gnawed-out holes in their gasters. However, this finding is consistent with earlier observations on a F. polyctena ‘bunker colony’ living in extreme starvation 37 , as well as with those of Mabelis 15 , who also found that the conspecific corpses (victims of the wood ant wars) retrieved into the nest were twice as heavy as those dumped on the waste piles. Moreover, he also proved that the contents of the corpse gasters were consumed and fed to the larvae through regurgitation 6 , 15 .…”

“…These findings suggest that extreme environmental conditions, such as food shortages, may promote corpse necrophagy among relatives in eusocial species. This is also supported by observations of a F. polyctena colony trapped in an underground bunker 37 . Moreover, the differences in the reactions of starving and fed colonies led us to the conclusion that the colony reacts in a post-stress situation by using available food sources in larger proportions than usual as if preparing for another similar situation.…”

“…In our study, we aimed to examine experimentally the modulating effect of pathogen contamination and starvation on cannibalistic necrophagy behaviour among nestmates. We chose Formica polyctena , as this species is already known to be cannibalistic 15 , 16 , 36 , 37 and the need for protein can be continuously present in a huge colony containing several (even thousands) queens 38 , 39 . Although cannibalistic necrophagy can ensure the survival of workers in conditions of food shortage 37 , the characteristics and drivers of corpse necrophagy were not investigated experimentally.…”

“…We chose Formica polyctena, as this species is already known to be cannibalistic 15,16,36,37 and the need for protein can be continuously present in a huge colony containing several (even thousands) queens 38,39 . Although cannibalistic necrophagy can ensure the survival of workers in conditions of food shortage 37 , the characteristics and drivers of corpse necrophagy were not investigated experimentally. In this study, we hypothesized that corpse necrophagy is an important phenomenon present during the handling of nestmate corpses in F. polyctena.…”

Consequences of Climate Change-Induced Habitat Conversions on Red Wood Ants in a Central European Mountain: A Case Study

“…The smaller nest mound volumes observed in the studied sites without coniferous trees could lead to decreased surviving chances of red wood ants in the changed habitats. Although they seem to be ecologically flexible and also can survive under extreme conditions [ 39 , 49 , 50 , 51 , 52 ], the disappearance of many nests in the disturbed habitats gives concern and calls for action from conservation managers. However, further investigations on a larger scale and with a larger sample size are needed to answer the still unresolved question, “How long can red wood ants (e.g., F. polyctena ) survive in a rapidly changing environment?” The results of our case study indicate that nest relocation would be advantageous before clear-cuttings and it would be important to plant mixed forest stands instead of monocultures in areas where the climate is suitable for native coniferous tree species.…”