It depends a lot on the temperament of the cats and the bun. Some buns are very bold and will chase cats away, some cats are very afraid of buns, and some will bother them more. My first cat used to try to chase my bun sometimes. That cat was more playful and the bun was more timid. I never allowed them out together unsupervised, and I would always play with my cat to distract him from the bunny. Basically if the bun runs from a cat, a cat will usually chase, which should be avoided as it’s stressful for the bun. It was also important not to give my cat any toys that were “rabbit sized”, like those grab and kick style toys, as they definitely learn what to play with that way.
I recommend starting slowly. Keep the kitties in a separate room at first, and swap some “scent soaker” items (like blankets, scratching boxes, etc) between the spaces. Once the cats are settled in to your home, feed them a their meal, and allow them into the bun’s room, but play with them and distract them. You don’t want them to be fixating on your bunny. Do not let the cats go into the bun’s pen or cage, as that’s his safe space. Keep introductions short. Basically you want the cats to be around the bun but uninterested in him. It may be easiest to introduce one cat at a time.
All of that said, I currently have 4 buns and 2 cats. 3 of the buns completely ignore the cats and the cats ignore them. Bun number 4 will charge the cats if he thinks they are in his space, so they are terrified of him and avoid him.
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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.