How much blood is needed for the dog to follow it?
This is the essential difference between a hunter’s ability to track a blood trail and a dog’s ability to do so. Most experienced hunters can visually follow a trail of fresh, bright red blood spattered every few yards in the daytime. A trained dog can follow a trail of blood that has dried to dark brown, with far less quantity on the ground, by scent alone (dogs are color blind), day or night. A human can typically follow fresh (same day) blood trails in quantities of around a pint splattered evenly along 100-150 yards on leaves, plants or dirt. A good dog can easily track that quantity of blood spread sporadically over 500 yards, and can follow almost imperceptively small droplets and smears.
