I would note that elephant immunocontrecption with pZP has been going on in South Africa since the late 1990s when a trial of the pZP vaccine was run in the Kruger Park. When that trial proved successful, a long-term project was started in the Makalali Conservancy close to Kruger on a herd of around 70 elephants in the Conservancy. The project has been remarkable successful. No contracepted cow has given birth (a 100% success rate!) unless it was already pregnant at the time it was darted with the contraceptive. A few years ago, five cows were taken off the contraceptive and, to date, three have given birth to healthy calves. The project has shown that the pZP vaccine is remarkable effective in elephants, is safe for females and for any calves who were in utero at the time of darting, does not disrupt normal social behavior and is reversible.

The article is somewhat equivocal on the reversibility issue and cites five references in support of "uncertainty" regarding reversibility. I would note that one of the references is incorrect (number 64 - Stout and Colenbrander 2005). We produced the book that purportedly contains the Stout and Colenbrander reference but it does not have any such article. I was able to find a 2004 article by the same two authors but they were referring to the GnRH vaccine, not pZP. The other papers were all published before the Makalali cows were taken off the contraceptive.

Interest in the use of the pZP vaccine to manage elephant populations in South Africa has expanded considerably in the past few years as the success at Makalali becomes more widely known. There are now a total of 14 reserves and conservancies in South Africa using pZP to manage their elephant populations with a number of others showing interest.

Andrew N Rowan
Chief Scientific Officer
The Humane Society of the United States
Washington, DC