Hi Gypsy, thanks for starting a new thread on this.

I didn't have to train my baby bunnies. Somehow they learnt from their mother and just pee-ed in the litter pan by the time they were 6 weeks old.

You could be right about marking territory. Sweet Pea is litter trained but when I switched cages for the bunnies a few days ago, she pee-ed all over the cage for a couple of days before deciding to use the litter pan again.