Keeping cool: How thermal landscapes shape ant foraging performance

Predictions of species’ vulnerability to global warming often rely on temperature averages, although many habitats have considerable thermal heterogeneity that can enable behavioral thermoregulation. This is especially important for ectotherms such as insects, which can use fine-scale thermal variation to maintain their optimal body temperature—for example, by foraging in cooler areas when it is too hot. We are investigating how thermal heterogeneity influences the foraging performance of the harvester ant Messor wasmanni, an ecosystem engineer. By comparing foraging differences between populations from two Mediterranean islands along a natural temperature gradient, we are also assessing the potential for thermoregulatory adaptation.

We are quantifying thermal heterogeneity around ant nests by combining high-resolution 3D drone thermal imaging with ground-based thermocouple measurements. Using a recently developed modelling approach, we will produce detailed spatio-temporal predictions of the thermal landscape for two studied localities. Preliminary findings revealed pronounced thermal heterogeneity across three different times of day and around nests. Heterogeneity was highest at midday, when the average temperature difference between hot and cold areas around nests was 5 °C, and the maximum difference reached 25 °C. To assess the influence on performance, we used in-situ video recordings to track ant foraging and measure changes in foraging speed. Uniting microclimatic and behavioral data will help uncover insects’ potential to cope with climate change.