Leaf-cutting ant workers (Acromyrmex heyeri) trade off nest thermoregulation for humidity control

Abstract

This study investigated whether workers of the thatching grass-cutting ant Acromyrmex heyeri respond to the competing demands of temperature and humidity control by modifying the architecture of the nest thatch. First, we evaluated whether the opening and closing of nest apertures are thermoregulatory responses. Second, we explored whether the control of nest humidity is compromised by the thermoregulatory responses, and to what extent workers trade off the control of one variable for the other. At temperatures ranging from 20–30°C, workers created more openings in the nest thatch, the higher the internal nest temperature. When the air surrounding the nest was experimentally desiccated at constant temperature, workers were observed to close nest openings at temperatures that previously triggered the opposite response, i.e., opening of apertures. This demonstrates that A. heyeri workers trade off a response related to thermoregulation for the maintenance of internal nest humidity.