I noticed a couple weeks ago that the bunnies had started occasionally going right next to the litter box. I had read somewhere that they can get confused by smells and "miss" the box, and the best thing to do is clean the area around the box and reinforce where they're supposed to poo. Their area needed cleaning anyway, so I washed blankets, vacuumed everything, and rearranged a couple things. Now, they go in the box during the day and whenever the light is on, but at night when the lights are off they still go right outside of it! Why only at night!? I'm pretty sure they can see in the dark, at least well enough that they shouldn't misjudge where the litter box is. It seems like an odd behavioral thing, so I was wondering if anyone has any idea or experience with this.