First of all, I’ve found with every one of my bunnies those little “Rabbit Side Litter Boxes” just do not work. My bunnies get to be bigger than a pound and BAM, they don’t fit. So do yourself the favor and just get the kitty litter box the FIRST time around! Plus, they’re about $10 cheaper and you’ll be able to use them forever, not just until your bun outgrows it. Unless you have a Flemmy. Then just get an X-Large one from the beginning! Once you’ve stocked up on the litter box – we can talk about actual Litter.
My favorite is wood pellets, like Feline Pine. It is super absorbent, reduces smell better than any other litter I’ve tried, and lasts longer than the others. Unlike pine shavings, it is rabbit-safe. Organic litters are always recommended, some others include: Cat Country, Yesterdays News, compressed sawdust pellets, straw, or hay. I have also used and liked Carefresh a lot — but it tends to be a little more expensive. Be careful and steer clear of litters such as pine or cedar shavings or chips as they are thought to cause liver damage.
Typically bunnies like to “do their business” in one area or spot in their house. Let them choose their spot and then put the litter box in this area. They will typically begin to use their litter box, if you do see accidents clean up any urine with a paper towel and throw the towel in their litter box to help them realize that’s where they should go. Throw any excessive poos inside the litter box also. If spayed or neutered, litter training shouldn’t be difficult (although some buns can be tricky). Give a smaller amount of space in the beginning to help encourage the bun to use his litter box in that space. Once they master one area, you can expand their areas – although if you expand too much bigger be sure to incorporate another litter box to deter from accidents.