Rumble without the strut?!

[LennyPig]

One of my piggies keeps making a rumblestrut noise but is not strutting. I have no idea who it is as no-one is moving around at all, they are all laid down. And every time I peep round my laptop the sound stops

Any ideas what this means?

 

[Briony_S]

probably someone throwing the weight around a teeny bit! Mine do it to me when they have had enough laptime and want to go back in their cages! no strutting just the noise and i'm like ok I'll put you back in and then they carry on being quite happy running around their cages!

It is nothing to worry about.