Why do animals who live underground appear always clean and not full of dirt? (e.g. worms, mice, rabbit)

Question

Why do animals who live underground appear always clean and not full of dirt? (e.g. worms, mice, rabbit)

In: 7599

Answer 1

That woukd be unnecessary weight. Organisms are designed to conserve energy. Some mechanisms for stopping things from clinging to them would tend to evolve over time.