Inbreeding depression on reproductive performance and survival in captive gazelles of great conservation value

Abstract

Here I present a detailed analysis of individual inbreeding coefficient effects on some reproductive parameters and longevity in three species of gazelles under different conservation status: vulnerable dorcas gazelle, endangered Cuvier’s gazelle, and extinct in the wild mhorr gazelle. The novelty of this study stems from the inclusion of both males and females in analyses including a large database of information collected during two decades of periodical studbook inventories for these species. Translocations to different zoo locations of the extinct subspecies mhorr gazelle do not apparently affect reproductive performance (population sex ratio) or individual longevity. In agreement with previous works, the average inbreeding coefficients vary inter-specifically, being higher in Cuvier’s, followed by mhorr and dorcas gazelles. This reflects the different population size of the founding individuals of each species’ captive population. Sexual maturity and age at first birth follow an allometric pattern, occurring at an earlier age in the smallest species (dorcas), followed by Cuvier’s and then the mhorr gazelle. Twinning in Cuvier’s gazelle depends on maternal experience, as it is less frequent in primiparous females. Inbreeding affects neither twinning nor sex ratio. Mhorr gazelles’ studbook shows several causes of death and it emerges that a higher proportion of non-inbred females die due to pathologies than males, although both sexes show similar proportion of mortal pathologies when inbred. Multifactor ANOVA shows that longevity decreases with inbreeding level and that females live longer than males in the three species of gazelles studied, as expected in polygynous mammals. Mhorr and dorcas non-inbred females show higher juvenile survival than males, whereas inbred individuals show a similar declining juvenile survival, particularly in mhorr and Cuvier’s gazelles. Finally, it is discussed the apparent inbreeding tolerance in Cuvier’s species, and the great value keeping and studying long term data of well-monitored captive populations may prove to the conservation of threatened species.