I need to point out that this statement isn't entirely correct. Though cardboard isn't usually harmful for rabbits to ingest in small amounts, if large amounts or large pieces are consumed, they do pose a possible intestinal blockage risk. There have been incidents where rabbits have developed an intestinal impaction due to excess cardboard consumption. Cardboard isn't really natural for them to be eating. It's a man made product that doesn't break down in the gut but compacts together into a gooey mass, which is why it can pose a blockage risk. Hay, forage, branches, vegetation. Those are natural fiber sources for them to eatCardboard is fine for bunnies to eat. I would give him small pieces of cardboard. and other toys that he can chew on. You may want to get the rubber wire protectors. Cardboard and paper is a natural thing for bunnies to eat. Just reduce the amount of cardboard that you give him. If you don't want him to eat cardboard then give him other chewing toys such as pine cones, willow, fruit tree sticks, etc. You have a bunny who is a chewer so it best to get things that he will enjoy chewing.