Report 5173: Large bipedal animal frequently observed by a South Dakota family

For the past four years my family has seen a creature unidentifiable to us; these sightings have been at our home seven miles north of Porcupine, South Dakota.  The creature appears to be seven to nine feet tall and has left a couple of footprints that measured 18 inches long and 7 inches wide.  It stands up straight and has a slight hunch when walking.  We have also found hair; possible saliva mixed with grass, and dried blood stains on cactus.  There have been small trees broken on the property; they look snapped which would take such strength.  It has often been seen running at high speed, too quickly to follow. I and most family members have seen this creature continuously – not just once; sometimes days pass between sightings.