Regulation of soil moisture by mound-building termites (Odontotermes obesus)

Abstract

Mound-building termites build large structure made entirely from soil. These mounds enclose their colonies and protect them from predators and natural elements. In addition to the termite colony and their brood, the mound also houses a fungus that is cultured by the termites, which in return helps the termite digest wood. For survival of the termites and the symbiotic fungus, the internal environment of the mound must maintain its temperature, humidity, and oxygen levels. It is also essential that termites be able to repair mounds if they are damaged. All of these tasks require a continuous supply of water. It is well-known that termite build long-lasting mounds in both water-logged and arid regions, which suggests that they must be able to sense and regulate soil moisture levels within the mounds. However, very little is known about how termites are able to regulate the moisture levels within their mounds. In large part, this lack of knowledge stems from the fact that it is very difficult to film termites within their subterranean environs. To address this question, we developed laboratory-based experiments in which we were able to directly visualize the water-transportation by termites. We next manipulated the water levels in soil patches and quantified the ability of termites to build under variable soil moisture conditions. These experiments reveal that termites actively transport water depending on the soil moisture levels, and that they show distinct time dynamics of the water transport. Our study provides novel insights into water transportation and soil moisture regulation by termites.