An Update on Elephant Immunocontraception

While the debate over culling elephants in the Kruger National Park rages on, work on the humane control of elephants in South Africa continues. The project has expanded to include seven additional game reserves with populations ranging from 10 to 90 elephants. The most recent of these is the Welgevonden Game Reserve, which has 90 elephants; we were able to contracept 43 cows. The fact that this was possible proves that much larger populations can also be tackled. Additionally, we vaccinated the first three elephant cows at the Kapama Game Reserve with a "one-shot" vaccine in November 2005.

This vaccine formulation has been tested extensively on horse populations in the United States and brings a new dimension to contraception of elephants and other wildlife. A single vaccination lasts approximately two years. The fact that we are working with captive elephants will allow us to monitor their antibody responses at regular intervals, giving us an early answer to the efficacy of the vaccine—instead of having to wait at least one entire gestation period of 22 months. Seven more cows will soon be immunized.


Another avenue we are following is immuno-control using a GnRH vaccine. Rather than blocking fertilization, antibodies produced in response neutralize endogenous GnRH, which normally stimulates the release of the gonadotropic hormones that control male and female gonads. Females stop cycling and males stop producing sperm and testosterone. Still, the method is reversible—contrary to vasectomies, which have been carried out on four or five elephant bulls (one of whom died under anesthesia). So far, we have used the vaccine on 14 elephant bulls to control aggressive behavior. We now intend to test the vaccine as a contraceptive in elephant cows.

Contraception is the ideal solution for controlling elephant populations, and in the future, it will only become more effective. Yet even with the current technology, it is possible to control large populations of elephants. Our models indicate that even with a contraceptive efficacy of only 60 percent, the growth of an elephant population can be cut in half over a period of 15 years. This means the current population of about 13,000 in Kruger would grow to only 20,000, instead of the 28,000 mark it would reach if left unchecked. Officials in Kruger deny that this is a problem that can be solved humanely, but we will remain dedicated to proving them wrong.

Article by Henk Bertschinger, a professor of theriogenology at the University of Pretoria.

The Politics of Population Control

Bertschinger responds to the claim by South African National Parks Head of Conservation Hector Magome that elephant contraception does not work.

  1. They did not even try it
  2. —we tried it. I had to lobby for years before they allowed us to do the first field trial, and even then, we were only granted permission after we had shown that there is homology between pig and elephant zona pellucida proteins used in the vaccine.
  3. Our goal during the first and second field trials in Kruger was to see if the vaccine could contracept African elephants
  4. —not to see if a population could be controlled. We were able to prove that unvaccinated elephants had a significantly higher conception rate.
  5. We have shown conclusively since then that we can contracept a small population of 60 elephants and bring about a zero population growth after only three years.