Isotopic shift in an introduced population of gemsbok (Oryx gazella)

We use isotope ratio mass spectrometry to examine the foraging ecology of an introduced population of gemsbok, Oryx gazella, in New Mexico, USA. Gemsbok in New Mexico exhibit an isotopic shift in carbon when compared to African gemsbok, suggesting that the introduced gemsbok include more shrubs (C3 plants) in their diets than do native African gemsbok. New Mexican gemsbok did not differ significantly in isotopic signatures according to gender, maturity, or reproductive status; they did exhibit significant patterns of fractionation in carbon and nitrogen isotopes between-tissue types (bone, muscle, and hair). Stable isotope analysis indicated that C3 plants (shrubs and forbs) may comprise up to 44% of the diets of gemsbok in New Mexico and that gemsbok diets may vary seasonally. These results are consistent with previously published fecal analyses. Stable isotope analysis appears to be a useful tool for rapid dietary analysis and may help wildlife managers to quickly evaluate the role of diet limitation or expanded diet breadth on the population dynamics of introduced species, and to examine the role of resource competition between native and introduced populations.