How do ants sense imminent rainfall?

Question

I have always been told to watch to see if ant-hole mounds are built up as a sign of imminent rainfall. My questions are, if what I have always been told is true, then by what mechanism do ants 'sense' the imminent rainfall? Is it a case of sensing air pressure drop, increasing humidity or both?

Answer 1

Several studies, including the one linked below from Ethology, suggest that ants can sense and respond to changes in air pressure, humidity, and temperature. I didn't find a consensus on which factors are the most important in allowing ants to predict and prepare for imminent rainfall, but in answer to your question I think it's safe to say they sense and respond to both pressure and humidity.

Foraging activity of leaf‐cutter ants is affected by barometric pressure - Sujimoto - 2020 - Ethology