Sleepless Footsteps is a script and technique that can be easily applied to your prefabs. The technique works well for humanoids, but could just as easily be applied for animals as well if you apply a different texture to the footprint plane.
I developed this script because I wanted a simple and realistic footprint effect that I can easily apply to all moving players and NPCs with minimal impact on performance.
Unity Asset Store
Please click this link to find Sleepless Footprints on the Unity Asset Store.