The influence of pZP vaccination on stress in female African elephants (Loxodonta Africana) in the Greater Makalali Game Reserve.

Abstract

In contrast to other parts of Africa where elephants are still endangered, elephant numbers in South African wild-life parks have risen to levels where they threaten biodiversity. One option currently being used for managing elephant population growth in the Greater Makalali Game Reserve is immunocontraception using the Porcine Zona Pellucida (PZP) vaccine. The anticipated effect of pZP immunocontraception is repeated episodes of sexual receptiveness not leading to pregnancy (Rasmussen and Schulte 1998). As a result, pZP vaccination is expected to result in repeateelevated stress levels in pZP vaccinated cows. The aim of this study was therefore to examine whether there is a correlation between the presence of an adult bull close to a matriarchal herd and indices of stress in the mature cows within that herd, and whether there is a correlation between progesterone concentrations i.e. the phase of the cycle of a pZP vaccinated elephant and circulating corticosteroid levels. During a 4 month period (March-June), behavioural observations were performed on, and feacal samples were collected from, pZP immunocontracepted cows in the Greater Makalali Game Reserve, Limpopo, South Africa. A total of 58 samples from 19 different cows were analyzed for 11-oxo-cortisol by EIA: Wasser et al. (2000) reported fecal 11-oxo-cortisol levels to be a reliable measure of the glucocorticoid stress response in African elephants. In the current study, fecal 11-oxo-cortisol didn’t vary with respect to the presence or absence of an adult bull, suggesting there is no significant stress response to the presence of a bull near a matriarchal herd. Nevertheless, the approach described provides a useful basis for further studies on the influence of pZP vaccination and resulting increased frequency of bull presence, on stress in elephant cows.