High environmental temperatures put nest excavation by ants on fast forward: they dig the same nests, faster
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Environmental temperature influences the physiology and the behaviour of ectothermic organisms, including ants. However, the complex collective behaviour exhibited by ant colonies means that it is difficult to predict how the effects of temperature translate to colony-level functioning and features, such as the form of their nests. This study aims to determine the effects of environmental temperature on nest excavation rate and on the morphology of excavated nests. To this end, we characterized the nest digging activity of the yellow meadow ant Lasius flavus confined to dig in a nearly two-dimensional experimental setup maintained at a constant temperature ranging from 15 to 30 degrees Celsius. Ants dug faster at higher temperature, with an increase of digging rate that reflected the temperature-induced increase of movement speed of individual ants. Nevertheless, the shape of excavated nests remained statistically unchanged across the full range of temperatures we tested. These results suggest a mechanism whereby temperature accelerates in a similar way all the activities involved in the nest excavation process, rather than disproportionately affecting individual components of the process, such as tunnel branching or elongation. The ability to produce a consistent overall nest structure, irrespective of the temperature conditions encountered at the time of digging, may provide adaptive benefits to the colony.
Significance
When temperature increases, ants move faster and their metabolism accelerates. Are the nests that they excavate also different? This question is not easy to answer beforehand because the complex collective regulations within an ant colony could either amplify or mitigate the effects of temperature on individual ant behaviour.
In our research, we found that the yellow meadow ants, Lasius flavus , dug significantly faster at higher temperature, but the shape of the nests that they excavated did not change. It is as if temperature sped up in a similar way all the activities involved in the excavation process, similar to the effect of increasing the playback speed of a video. Given the importance of nests for ant colonies, there might be a benefit in producing nests with stable characteristics, irrespective of the temperature experienced when the excavation took place.
