Buttercups?

I have always believed buttercups to be toxic to rabbits and have been careful to eradicate them from the back garden where the rabbits free range, but the other day I was watching Rosie enjoy a particularly large dandelion and as it disappeared it revealed a dreaded buttercup plant behind it. Before I could stop her a whole leaf of that had disappeared too!
I got rid of the rest of the plant and kept an eye on her but she has shown no ill effects at all. I wonder how much a bun would have to eat before it harmed them and what do bunnies do in the wild where there are no gardeners to weed for them?

The bulb and sap and leaves of the Buttercup are toxic to rabbits if Rosie has no sign's of ill effect that's good just keep an eye on her. We have loads in our garden and I have to go round and pick them all or sometimes it's easier to just get the lawnmower out.