Leopold is deaf. I remember the vet looking in his ears long ago when I told her I suspected he was deaf. She couldn’t see anything “wrong”, meaning there was no infection or anything. He is a Holland lop and deafness is relatively common in the breed. Something about dwarfism and lop ears don’t work well together. Everything is smooshed.
One of the tests we did with Leopold was the treat bag test. But I had to remove Wooly from the room because Leopold is usually clued in about what’s happening if he sees Wooly react. I put Wooly on the sofa in the living room. Then I went to their room and stood in the doorway. I held the treat bag up so it was behind the wall and out of Leopold’s view. I crinkled the bag. Leopold went about his business. I crinkled the bag louder. Still no reaction. Then I felt little paws on my leg. I looked down and Wooly had found his was down the hallway. Nothing wrong with Wooly’s hearing, that was for sure. *sigh*
We did some other tests too. Leopold just doesn’t react to anything and it is very easy to sneak up on him as long as you avoid casting a shadow within his line of sight. I have scared the crap out of him quite a few times because he just didn’t know I was there. He doesn’t come when called. He likely has no clue what his name is. Wooly knows his name and he knows what the word “treat” is and he knows what “no” means.
Another thing we noticed about Leopold that would be consistent with him being deaf is that he has never made a single sound. Now I know many bunnies are not really vocal. But he has never made any sound at all. Not a growl, grunt or honk, nothing. When he thumps, and it isn’t too often, it’s like he doesn’t know how loud he is. What I mean is, he will thump so hard I’m surprised he hasn’t broken his foot. It’s as if he thinks he needs to thump super hard so he can feel the vibration better. He also bites. It isn’t a nip. I think he thinks it is a nip. But it isn’t. He bites HARD and it hurts. He will do this particularly when he is frustrated. With Wooly, it only took a few squeals to get him to no bite hard. Wooly only lightly touches you with his teeth now and that is only if he’s really had a enough with grooming. So I think that is further evidence that Leopold never learned some basic bunny social etiquette because he simply cannot hear thumping or vocalizations.
ETA: Leopold is also kind of clumsy. Apparently deaf humans can have balance issues since balance is maintained within the ear. So I often wonder if it would be similar in deaf rabbits.