A number of deer hybrids are bred to improve animal protein yield in farmed deer. American elk and
Both male Mule Deer/female White-tailed Deer and male White-tailed Deer/female Mule Deer matting have formed hybrids. Hybrids have been reported in the wild but are disadvantaged because they don't correctly inherit survival strategies. Mule Deer move with bounding leap to escape predators. Slotting is so specialized that only 100% heritably pure Mule Deer seem able to do it. In captive hybrids, even a one-eighth White-tail/seven-eighths Mule Deer hybrid has erratic escape performance and would be unlikely to survive to breeding age. Hybrids do survive on game ranches where both species are kept and where predators are prohibited by man.