Effects of PzP-vaccination on the oestrous cycle of female African elephants in the Makalali Game reserve, South-Africa

Abstract

Abstract Currently, the extremely high density of elephants in many large parks in South Africa, Zimbabwe and Botswana is considered an ecological problem. To control elephant population growth, the following options have been proposed; culling, range expansion, translocation, contraception and non-intervention (in the expectation of natural self-regulation). This study addressed the following questions: Do pZP-vaccinated elephant cows exhibit oestrus at the expected 16-17 week intervals? If so, what is the influence of the more frequent oestrous periods on the behaviour of both male and female elephants? The absence of a clear increase in the frequency of oestrous periods could be simply because many oestrous periods are missed as a result of the fragmented behavioural observations. Another possibility is that pZP vaccinated cows do not show oestrus at the expected 12-16 week intervals i.e. that the vaccination interferes with cyclicity. Interaction of family groups containing with pZP vaccinated with adult bulls has not been altered by pZP vaccination and these interactions do not appear to affect the behaviour of the cows. Neither is there any evidence that presence of the bulls is stressful to the matriarchal groups or that the failure to produce calves affects structure of the groups (family groups have not fragmented after 10 years of pZP vaccination), or the dominance hierarchy within a group.

In conclusion, there is currently no evidence that pZP vaccination for up to consecutive years leads to serious side-effects in treated animals or their family groups. To be sure that there are no side-effects in the longer term, this study will be continued for a number of years. pZP vaccination will not solve the problem of the overabundance of elephants already in southern Africa, but may be a valuable component of a concerted strategy to prevent the problem worsening or recurring after a more drastic intervention to reduce population density in the short term.