I'm sure mammals require more effort (staying downwind, etc), but I've never attempted to photograph them.
Mammals can be easy. They let you get nice and close sometimes. Just make sure any bunnies you try to take pictures aren't from Caerbannog...
I'm afraid I had to look up that reference
I have done rabbits, actually. They used to forage in front of a fixed bird hide at my local nature reserve. Feral British rabbits always seen very timid otherwise, though.
You won't believe that if you watch this:
|Holy Grail - Killer Bunny||Small | Large|
Reference is to Monty Python and the Holy Grail.