Effects of immobilization on fertility in female black rhino (Diceros bicornis)

Forty-six female black rhino were immobilized 113 times in the Sinamatella Intensive Protection Zone, Zimbabwe, from August 1992 to October 1997. The effects of immobilization on inter-calving interval (ICI), calving rate (ca lves/female/year), conception and calves born/year were assessed. The mean ICI (n=17) was 40.24+/-4.96 months. There was a significant linear relation ship between the number and interval of immobilizations in the preconceptio n interval (PCI) and duration of ICI; further investigations were made to o vercome possible effects of temporal autocorrelation. Both a non-linear mod el and a general linear model (with five independent effects) showed a sign ificant relationship only between the ICI and mean immobilization interval in the pre-conception interval (PCI), but not the mean immobilization inter val in the whole ICI (including gestation immobilizations). Both suggested that the relationship between immobilization and inter-calving interval was not the result of temporal autocorrelation and that the immobilization reg ime significantly affected the ICI. Using the calving rate as a response va riable, five effects were tested in a general linear model. Only the immobi lization rate in the PCI was significant. For conceptions per calendar mont h, we examined two effects in a general linear model: the number of mature females immobilized each month, and rainfall in the month of conception plu s 2 previous months. Both effects were significant. For the number of calve s born/year, the effect of the immobilization regime (the number of mature females immobilized/year) and rainfall were examined. Only immobilization w as significant. We suggest that the unusually intensive immobilization regi me undertaken at Sinamatella has negatively impacted on female fertility, a nd discuss possible mechanisms. We also suggest the need to adopt guideline s to minimize the impact of immobilization on fertility in female black rhi no.