[header] How to tell when gerbils are mating [title] Listen for thumping sounds. [step] You may also observe the gerbil pounding both rear feet. The sound is usually a quick thump, but can vary in tempo and volume. 
This can be mistaken for the gerbil being excited for reasons other than mating. [substeps] Sometimes gerbils other than the mating pair will " catch on " and start pounding their feet too.