Correlation between progesterone and glucocorticoid metabolite concentrations in the faeces of free roaming African elephants (Loxodonta africana africana).

Abstract

Elephant populations in Southern Africa have been increasing in number following their protective status as endangered species by CITES in 1989, to the extent that elephant populations have to be regulated. Elephant population control can be done in two basic ways: decreasing their number (i.e. culling or relocation) or preventing further increase by reduction of their reproductive rate (i.e. contraception). Culling elephants is an effective but controversial method due to public disapproval, while translocation is a less suitable method due to various practical problems. Contraceptive methods should ideally meet certain prerequisites based on efficacy, minimal animal handling, reversibility, safety for use in pregnant animals, minimal health side effects, no passage through the food chain, minimal effects on behaviour and low costs. Contraceptive methods as surgical sterilization, mechanical and hormonal contraception do not meet all of these prerequisites. Immunocontraception has become a point of interest with the antigens zona pellucida (ZP) and gonadotrophin-releasing hormone (GnRH) most intensively studied. GnRH is a neuropeptide produced by the hypothalamus and plays a crucial role in hypothalamic-pituitary-ovarian axis involved in ovulation. By vaccinating against GnRH, antibodies are thought to bind to GnRH, thereby blocking an important step in the ovulation process. The ultimate purpose of GnRH vaccination is to induce infertility by returning treated animals to a (temporary) pharmalogical pre-pubertal state. The eventual aim of this study was to test a commercial GnRH vaccine, Improvac®, for its effect on female African elephants. In this current pilot study we measured the progestagen and glucocorticoids metabolite levels in the faeces of two African elephant cows during an entire oestrus cycle (20 weeks) prior to GnRH vaccination. The faecal concentrations were estimated using Enzyme Immuno Assays (EIA) for 5α pregnane-3-ol-20-one (progesterone metabolite) and 3α,11-Oxo-cortisol (glucocorticoid metabolite). The aim by doing so was to provide a baseline for faecal progestagen and glucocorticoid concentrations in cycling non-pregnant African elephant cows and investigate correlations between reproductive status (progestagen) and stress (glucocorticoids) using a non-invasive sampling method. - 3 - Although the number of samples analysed in this study was limited, it did demonstrate that faecal progesterone concentrations could be used to demonstrate luteal activity, making it of considerable use for assessing the effects of GnRH vaccination. Faecal glucocorticoids levels did not appear to be significantly influenced by stage of cycle. A complete database of glucocorticoids levels during the long term studies could be helpful to determine whether GnRH vaccination is detrimental to welfare.