A big part of this equation is “time”……As you go from 1 hr after the shot…. to 4 hrs ….to 12 hrs….. to 24 hrs these scents that the deer leaves behind start to dissipate and they don’t do it at the same rate. What the dog is able to detect an hour after the shot is different than what they can detect at 24 hrs…... Yes, a dog likely does track the deer itself through a combination of scents….one of which being interdigital gland scent…. IF you get on the track soon enough…..However, I think that after a certain amount of time has gone by then the dog is tracking on blood alone.