What is being used is called an immunocontraceptive. This is because it does not work in the same way that a human contraceptive works; i.e. it does not rely on the sex hormones of either of the elephants. Instead, it uses proteins that have been extracted from a sow’s (female pig’s) egg or ovum. These proteins are called porcine zona pellucida. These function to stop the sperm from binding with the egg and from penetrating and fertilising it. Although it was first tested on elephants, it is now used on dozens of other animal species.
In the first year of receiving the contraceptive, the elephant will need to be administered three doses of the vaccine separately. Thereafter, the animal will only need one dose every year to ensure that she does not get pregnant. This has been found to be a safe and reliable method of contraception in elephants. Significantly, it is also reversible. This means that the elephant can be taken off her contraception to allow her to have a calf when the population numbers are down sufficiently. The contraception can be administered during pregnancy with no negative effect on the unborn infant or its mother.
There are no significant known side effects to this form of contraception, apart from the elephants’ avoiding the vehicle from which it is administered in some cases!
Before immunocontraception was developed, researchers attempted to use medicine that had a steroidal base or one of sex hormones. However, the increased hormones caused the males to harass the females without let up. This, in turn, forced the cows away from the herd and their young in an attempt to escape the males.
One of the few suspected negative implications lie in the fact that elephants are, by nature, social animals that value families. Inhibiting their abilities to procreate may have some long-term effect on the social structure, roles and responsibilities within the herd. Cost implications may have a bearing on some of the less financially well off parks and reserves.
While this is not a solution to existing overpopulations of elephants, it is a prevention against reaching such a situation in the future. This carries important advantages – both environmentally and financially.