9th International Deer Biology Congress

AUTHORS: James R. Heffelfinger, Arizona Game and Fish Department, Phoenix, AZ

ABSTRACT: Different species of animals, even those closely related, are normally kept from reproducing through reproductive isolating mechanisms such as: geographic isolation, breeding season timing, occupying different types of habitat, or by having different courtship and breeding behavior. In the case of white-tailed and mule deer, all these factors help keep the two species from hybridizing. These mechanisms have worked remarkably well throughout their evolutionary coexistence. However, in rare cases these isolating factors break down resulting in interspecific hybridization. Hybrids of these two species have been reported from captive facilities as early as 1898 when a whitetail x mule deer cross was produced at the Cincinnati Zoo. Male hybrids are sterile, however, female hybrids are fertile and can breed back to either of the parental species. This hybridization in Odocoileus is rare in most areas, but does occur where their ranges overlap. Hybrid deer show characteristics that are intermediate between mule deer and whitetails but most are not universally diagnostic of a hybrid individual. The most informative physical feature to diagnose a hybrid in the wild is the size and location of the metatarsal gland on the outside of the lower portion of the rear legs. Two loci visualized by protein electrophoresis have been used in the past as a genetic test of hybridization. New advances in genetic techniques have been developed and are now being employed to learn more about hybridization in Odocoileus. In addition to the identification of F1 hybrids, a suite of microsatellites appear to offer some clarity regarding the results of backcrossed individuals.