Possible gerbil stereotypic behavior?

I no longer have gerbils, but when I did I noticed that they would jump up and (quite loudly) hit the mesh top of their tank. They would do it once, pause, then do it again. This was usually at night. As I learned more about enrichment and gave them more foraging toys and deeper substrate, I noticed that they would rarely exhibit the jumping behavior. I'm pretty sure the jumping was stereotypic, but the only gerbil stereotypic behavior I had ever really read about was gerbils digging in the corner of their tank constantly.

Would this behavior be classed as stereotypic? Or could they just have been really weird and enjoyed it? 
Has any other gerbil keepers experienced this particular behavior before?