I have a spayed female holland lop bunny named Bubba who is about 4y old. She was never into digging before, as she has gotten older, she now digs like clockwork! 

She always digs in the evening or in the early morning, specifically when the sun rises and sets. She can go on doing this for several minutes uninterrupted. I also noticed that it usually gets worse when the weather changes and it gets colder. I tried getting her a sand-box or dirt-box figuring she might enjoy that but she would rather dig on harder surfaces in her enclosure. She does not do this in the carpeted area or her actual litterbox either (thankfully) but she will on the linoleum area where her food usually is. 

I thought it might have to do with her nails but I clip them once a month so I don’t think that is the issue. Also, my boy rabbit Poe never engages in this behavior. 

It doesn’t bother me at all, but I am curious…can anybody give me an explanation as to why this happens? Thanks!