resting position

Question

2 rabbits   The dwarf often rests on the bigger one as shown.  Does she do that to keep warm?

Answer
Tom,

First thing I'd need to know is: are both bunnies fixed? If they aren't then I'd recommend doing that sooner rather than later as these mounts can lead to aggression and injury.
If they are, then good news - it's one of a few things:
Dominant bunny - typically one bunny in a pair (or group) will be the dominant bunny. The size of the bunny has nothing to do with who's boss either. This could be a display of dominance and would typically be followed or preceded by a request for grooming, which is showcased with dominant bunny presenting a lowered head towards the submissive bun.
Cuddling bunny - could be your bun just wants to cuddle. This is part of why rabbit experts recommend having two together, since bunnies are incredibly social and use physical contact as a way to reinforce bonds.

Hope this helps Tom. Best of luck!