system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do animals who live underground appear always clean and not full of dirt? (e.g. worms, mice, rabbit)
gpt
Well, mice and rabbit both share 2 things in common. Constant grooming and they live in dens. Dens aren't full of loose dirt. But all the same they spend half of their day grooming. Not because they care how they look, but because a clean coat works better as insulation in the winter and to keep you cool in the summer, and whiskers are SUPER sensitive and work best clean. 

Worms have a slimy coating between them and what they burrow through. It lubricates them to help them move and prevents drying out as fast since the goop they make doesn't evaporate as readily as water.