In the late-1980s, Dr. Valerius Geist, professor of environmental sciences at the University of Calgary, set out to discover why mule deer and whitetails seem incapable of coexisting. His eight-year study revealed that one-way hybridization is the likely culprit. According to Dr. Geist's findings, when whitetail bucks breed mule deer does, the offspring lack the survival instincts of either species and thus are unable to cope in the wild. "Mule deer and whitetail deer have completely different escape strategies," explains Dr. Geist. "A mule deer usually reacts to danger from a great distance, fleeing at the first sign of trouble. When threatened, a mule deer throws obstacles at its pursuer, running uphill or bounding over trees and brush. "A whitetail, on the other hand, usually remains calm, sitting out a threat until the last possible moment, then flushing like a rooster pheasant racing away on a fairly straight line, using speed rather than obstacles to put distance between itself and a predator." Hybrids produced by a whitetail buck and mule deer doe don't demonstrate
either of these escape strategies. In fact, hybrid fawns seem to inherit a fatal blend of survival techniques that turn them into "sitting ducks.
I have Dr. Geist's book and have read it several times, along with Jim Heffelfinger's books. I also met both guys and talk to them considerably, during the years of to my early involvement in the Mule Deer Foundation. But nothing in nature is written in stone, especially deer behavior.
Have seen mule deer bucks run off whitetail bucks during the rut on Montana riverbottoms where both exist, very close to each other. In each instance the buck with the larger antlers ran the other off, whether it was a mule deer or whitetail.
