Also don't just track the blood, an injured deer usually leaves a good trail. The blood is more just for conformation your on the right trail.
I think I read somewhere you are in the military Patton, if you ever get the chance try to catch one of TTOS's tactical tracking schools. The skills you learn in that course really made me a better wildlife hunting tracker. The final test we had to track an instructor for over 3 miles with a 5 man team. Makes tracking a wounded deer much easier.
Shootmoore
