Suchergebnisse

Globally, African savanna elephants have been assessed as 'endangered'. Consequently, additional threats and losses due to human–elephant conflict (HEC) could further exacerbate the species' decline. In stark contrast, South Africa's elephant populations are mostly confined within fenced-in reserves that impede natural processes such as migration. As ecosystem engineers, elephant population growth herein should be limited. Within South Africa, elephant management has evolved as differing wildlife philosophies from utilitarian conservation ('nature for man') to biocentric preservation ('nature for nature') and a combination thereof, have been practiced. Traditionally, both HEC and population control have been largely synonymous with lethal control, i.e. culling. However, with the increase of public or expert input to Policy, lethal control is not favoured by the public. As an alternative, immunocontraception of female African savanna elephants through non-invasive, native porcine zona pellucida (pZP) vaccinations has been employed successfully and is currently adopted in 43 elephant reserves across South Africa. Current legislation now recommends culling as the last population management resort. Newly promulgated legislation calls for wellbeing and welfare to be carefully measured in all biodiversity management decisions taken to minimise threats to biodiversity. As a keystone species, elephant is a direct driver of biodiversity change. Accordingly, and in light of these developments, all population management options, including immunocontraception, must be fully considered in South Africa's largest national park, the Kruger.

The aim of this study was to evaluate the effect of active immunisation against GnRH on ovarian activity and serum progesterone concentrations in a large group of mares (10 control and 55 experimental) under field conditions as a model for wildlife species such as zebra and African elephants. Within the experimental group, mares were subdivided into three age categories: Category 1 (4 years and younger, n = 26), Category 2 (4–10 years old, n = 18), and Category 3 (≥11 years old, n = 11). Experimental mares were vaccinated intramuscularly with 2 mL (400 μg) of the GnRH vaccine Improvac (Pfizer Animal Health, Sandton, South Africa). Control mares received the same amount of saline solution. The vaccinations were repeated 35 days later. The ovaries and reproductive tracts of each mare were examined by means of rectal palpation and ultrasonography on Days 0, 35 and 70. Blood was collected weekly for determination of serum progesterone concentration until Day 175. On Day 35 after primary vaccination all of the control mares and 14.5% of the experimental mares showed evidence of ovarian activity on the basis of clinical examination and serum progesterone concentration. On Day 70, all control mares and none of the experimental mares showed evidence of cyclic activity. No age-related effect within treatment groups was found. The serum progesterone concentration indicated that all experimental mares remained in anoestrus until Day 175. Five of the control mares fell pregnant between Days 35 and 70. The five non-pregnant control mares continued to cycle until the end of the observation period. Having achieved such promising results in this trial we now plan to test the GnRH vaccine in Burchell's zebra mares and African elephant cows.