Immunocontraception in Elephant Management

What have we learned in the last 20 years?

Immunocontraception is a non-steroidal, non-hormonal, non-invasive method of reversible contraception that is administered through a vaccination. The drug comprises a protein-based component called porcine zona pellucida (PZP) extracted from the ovaries of domestic pigs. The zona pellucida (ZP) is the membranous coating that surrounds all mammalian eggs. When PZP is injected into a female elephant, her body produces antibodies that bind themselves to the sperm receptor sites around the capsule surrounding her egg. The shape of the sperm receptor sites are changed, meaning that the sperm has nowhere to attach itself, and thus fertilization and pregnancy is prevented.

Having demonstrated the vaccine’s efficacy in the Kruger National Park (KNP) field trials, the technique was fine-tuned and then applied in the Greater Makalali Private Game Reserve (GMPGR), a private game reserve in South Africa. The objective here was to determine if the vaccine could be used as a remotely deliverable population control mechanism in wild, free-ranging elephant. The project which began in GMPGR in 2000, was first tested on 18 elephants. As of 2016, 26 cows are under treatment and the method has shown almost 100% efficacy.

What have we learnt that over the last 20 years demonstrates that immunocontraception is the obvious choice for controlling elephant populations?

  • No immobilisation of the animals is required; the vaccine is administered remotely by means of a drop-out dart.
  • Implementation is quick and efficient and complete within a few hours.
  • The vaccine does not affect pregnancies in progress, so if a pregnant female is vaccinated, she will carry to term and the offspring remains unharmed.
  • A 12-year behavioural study on the GMPGR elephants published in a peer-reviewed journal demonstrated that individual elephants showed no sign of physical or behavioural anomalies either in the short- or medium term. Herd and population behaviour, as well as sexual selection processes, remained unaffected despite the decline in the number of calves within the herds and the increased frequency in oestrus (as fertilisation is prevented).
  • This method is target specific and does not affect any other animals either directly or indirectly.  Once administered, PZP is easily assimilated by the body and hence does not pass into the food chain.
  • Reversibility has been demonstrated within the short to medium term.
  • The reduction of calving for defined periods can be compared to extended intercalving intervals experienced as a result of episodic natural catastrophes (e.g., drought or predation). Thus, natural processes are simulated.
  • Immunocontraception allows cohorts of births to occur, simulating natural gaps in recruitment in more natural low-resource conditions.
  • Immunocontraception allows elephants to occupy the same space but at lower overall numbers over time.
  • This method has dramatic effects on population numbers and prevents populations from doubling.


 Julien Naar, Patricia Huon. March 2015.

Currently > 700 female elephants in 22 protected areas ranging from 2,000 – 96,000 ha are being treated with immunocontraception in South Africa. Within the last two years alone, PZP has been adopted by three provincial parks (Ezemvelo KZN Wildlife’s Ithala, iSimangaliso Wetland Park and Hluhluwe iMfolozi – largest park and population) and one national park (Addo). Within these populations, the growth rate is managed in accordance with the carrying capacity of the site-specific habitat as well as the innate social and spatial nature of the species.

PZP-immunocontraception presents a proactive means of population control in elephants. If immunocontraception is not implemented, then the consequences of alternative methods, such as culling, must be fully examined and considered. In a world where an elephant is killed every 15 minutes for its tusks, do we really want to add to this number through culling, when a safe, humane alternative has been demonstrated to exist?

To answer any other questions that you may have, please visit

Audrey Delsink, Greater Makalali Private Game Reserve, Humane Society International, P O Box 1009, Hoedspruit, 1380

In collaboration with Prof. Henk Bertschinger1, Dr Jay Kirkpatrick2 and JJ van Altena3

1 University of Pretoria, Section of Reproduction, Department of Production Animal Studies, PO Box 75058, Lynwood Ridge 0040, South Africa

2 ZooMontana, Science and Conservation Centre, 2100 South Shiloh Road, Billings, MT 59106, USA

3Global Supplies, P O Box 1148, Highlands North 2037, South Africa


Ahlers, M., B. Ganswindt, S. Münschera, and H. Bertschinger. 2012. Fecal 20-oxo-pregnane concentrations in free-ranging African elephants (Loxodonta africana) treated with porcine zona pellucida vaccine. Theriogenology 78:77–85.

Benavides Valades, G., A. Ganswindt, H. Annandale, M. L. Schulman, and H. J. Bertschinger. 2012. Non-invasive assessment of the reproductive cycle in free-ranging female African elephants (Loxodonta africana) treated with a gonadotropin-releasing hormone (GnRH) vaccine for inducing anoestrus. Reprod Biol Endocrinol 10:63.

Bertschinger, H., A. Delsink, J. Kirkpatrick, J. van Altena, M. Ahlers, T. Dickerson, D. Powrie, and A. Burger. 2012. Porcine Zona Pellucida Immunocontraception of African elephants (Loxodonta africana): Beyond the experimental stage. Pages 95-102 in IVth International Wildlife Management Congress – Cooperative Wildlife Management Across Borders: Learning in the Face of Change. The Wildlife Society, 9 – 12 July 2012.

Delsink, A., and J. Kirkpatrick. 2012. Free-ranging African Elephant Immunocontraception: A New Paradigm for Elephant Management. Page 28. Humane Society International, Cape Town.

Delsink, A., J. Kirkpatrick, J. van Altena, H. Bertschinger, S. Ferreira, and R. Slotow. 2013a. Lack of spatial and behavioural responses to immunocontraception application in African Elephants (Loxodonta africana). Journal of Zoo and Wildlife Medicine 44:S52-74.

Delsink, A., A. Vanak, S. Ferreira, and R. Slotow. 2013b. Biologically Relevant Scales in Large Mammal Management Policies. Biological Conservation 167:116-126.

Druce, H., R. Mackey, K. Pretorius, and R. Slotow. 2013. The intermediate-term effects of PZP immunocontraception: behavioural monitoring of the treated elephant females and associated family groups. Animal Conservation 16:180-187. Accessed 23 September 2015