The north-south orientation of Australian termite mounds is due to the Sun and local wind: A heat transfer investigation

摘要

The Australian "magnetic" termite mounds are famously known for their systematic wedge-shape and north-south alignment. Although the longer axis of the mound wedge is mainly aligned north-to-south, depending on their locations, they might have slight deviations from true north, exhibiting consistent east or westward orientations. The structural characteristics of Australian mounds have been the subject of many in situ investigations in the past, suggesting that the orientation of these structures might be a response to termites' need for having a sort of thermal regulation within their habitat. Using the foundations based by the observational studies, this study develops a thermo-physics based predictive model, founded on the principles of heat transfer and thermodynamics, to fundamentally investigate the reason behind the shape and orientation of magnetic mounds. Using the typical environmental conditions of the locations where these mounds are found, the shape and orientation of the thermally optimized structures were successfully predicted by the model, indicating that their structural characteristics arise as a response to the combined effects of the local solar irradiance received on the mound body and the local wind condition. These combined effects result in a thermally regulated medium within the mound (i.e., uniform temperatures throughout the structure with minimum fluctuations throughout the day) that provides a suitable microclimate for the residing termites. The effects of different environmental conditions on the mound structural characteristics are also investigated.