The effect of pZP vaccination on the cyclicity of female African elephants in the Makalali Game Reserve

Abstract

As a result of conservation measures, the elephant population of South Africa has grown to a point where it is causing damage to the habitat and threatens biodiversity. Theoretically, there are several ways to control elephant population growth. Currently, immunocontraception with pZP (porcine zona pellucida) vaccine appears to be the most widely accepted option, both on human grounds and on the basis of efficacy. However, before wide-scale use of pZP vaccination can be recommended, further research into the possible longer term side-effects is required. The general aim of the present study was to examine whether pZP vaccination affects the frequency of oestrous in the African elephant. Another important aim of this study was to determine whether progesterone metabolite concentrations in the faeces were a more reliable way of detecting oestrus in African elephant cows than behavioural monitoring. Behavioural observations and faecal samples were collected from elephants in the Greater Makalali Private Game Reserve. Only 7 cases of oestrous behaviour were observed during a period of sixteen months. However, this may be an underestimate since oestrous behaviour is difficult to identify in elephants, partly because various indicators are used but primarily because the elephants can not be watched 24 hours a day every day; in all probability, numerous incidences of oestrous behaviour were missed. The faecal samples were supposed to be analysed with an ELISA for 5α-reduced progestin concentrations. However the antibody initially used for this analysis was not sufficiently sensitive, and the replacement did not arrive in time for this study. As a result, it is not yet possible to make firm conclusions about cyclity in pZP vaccinated elephants.