So my rabbit, Poopy, is about six years old now, and he’s a type of rex rabbit- so he’s not a spry little bun anymore. Recently, he’s been doing this strange thing where he kind of whines/whimpers when using his litter box. At least, that’s the best I can describe the sound. He’s very well-trained with the box and uses it religiously, except for some little territorial poops left around the house. When he’s out and about the place, he doesn’t make any strange or unusual noises. It only happens when he’s using his box, and it doesn’t happen every time, but enough to cause concern. 

What confuses me even more is it’s not like he looks uncomfortable. He’s still nibbling on his hay while he’s using the box, his ears aren’t flat, he looks as alert and content as ever. I haven’t changed his litter or the litter box at all, so I doubt it’s an issue of environment. Outside of the box, I haven’t seen any indication of GI statis or gas build-up (he’s had GI stasis before, so I’m unfortunately well-acquainted with the warning signs). He doesn’t press his belly, his stomach isn’t hard, and he’s about as active as an older bunny should be. 

Is he actually whimpering? Or is he passing gas? Can rabbits fart? Sorry, guys, I don’t even really know what to ask.  But is this normal, or does this sound like a red flag?