Elephants are intelligent and empathetic creatures, capable of expressing a wide range of human-like emotions. But their complex nature contributes towards the difficulty of their management, particularly when it comes to population control.
While elephants are a keystone species – they transform the savannah habitat and influence ecosystem function – their impact on vegetation can become destructive if population size is left unchecked, often eliminating certain species from the ecosystem. For this reason elephant populations have to be managed intensively, especially where conserving for high levels of biodiversity.
Historically, culling was the predominant method used to regulate elephant populations, but an increase in public pressure resulted in elephant culling being officially banned in 1995.
Although this was a step in the right direction, elephant numbers started to climb out of control. The porcine zona pellucida (pZP) vaccine is a versatile molecule that provokes an immune reaction in cows, causing them to produce antibodies that bind to the surface of their eggs. This prevents sperm binding and fertilisation.
In 1999, researchers confirmed that the vaccine could be used to stop elephant cows from conceiving. In contrast to hormonal contraceptives, pZP is efficient, reversible, safe, remotely deliverable, and has minimal impact on elephant social behaviour.
Application was tested in 2005 at seven private reserves, including Welgevonden Game Reserve in Limpopo, where it was incorporated into the wildlife management strategy. Over nine years, 108 cows were treated and monitored, and research showed the vaccine was highly effective as a birth control mechanism. It is 100% safe at any stage of development, remotely deliverable, and does not require animal immobilisation. It is 100% effective and sufficient in achieving a population growth rate of 0%.
Since its initiation, elephant contraception with the vaccine has become an integral component of Welgevonden’s elephant management. “The use of pZP has provided small- to medium-sized reserves with the opportunity to maintain a viable population of elephants with minimal impact on reserve biodiversity without sacrificing game-viewing opportunities,” says Matthew Thorp, Welgevonden elephant monitor.
The vaccine is aerially administered, with each individual cow being darted with a biodegradable dart that falls out once the immune-contraceptive has injected into the bloodstream. The intelligent dart ensures that no cows receive a double dose by spraying a coloured dye onto the rump of the elephant.
The vaccine does not halt population growth immediately and populations can take up to three years to stabilise. While it would be possible to inhibit births from this point onwards, calves are integral to herd cohesion and certain individuals are ‘skipped’ during contraception to ensure that herd dynamics remain as natural as possible.
Currently, 22 protected areas ranging from 2 000 to 96 000ha make use of pZP, including Addo National Elephant Park. pZP has proven to be a realistic alternative management tool in controlling elephant populations, particularly where it is used as part of a long-term management strategy.
Written by Jessica Oosthuyse
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