Why do foxes jump in the snow in winter?

The fox is a predator. The main prey for her in winter and summer are mice. It is easy to catch them in summer, but with the arrival of winter, it becomes more difficult for a fox to find food for itself. When she hears a rustle under the snow, she has to jump and force her paws and muzzle into the snow so that the prey does not run away. If the fox starts digging up a place from the snow, where she heard a rustle, the mouse will simply run away and the fox will remain hungry. Therefore, she has to jump a lot.