Elephant population growth unsustainable for size of Addo National Park

Historically, elephants were widespread in Africa, from the Mediterranean in the north, to the Cape.

In southern Africa, local San inhabitants led early European settlers into the interior, where they encountered herds of elephant.

This area is still rich in San rock art depicting elephants work by Paterson and Parkington (2007) concluded that the San had been “symbiotically, symbolically and spiritually linked to elephants” over tens of thousands of years.

They did not see elephant as a commodity but with the settlers came the demand for ivory elephants were seen as “valuable” in Europe and there was a perceived endless resource in Africa. But hunters, traders and settlers in the hinterland took their toll on the elephant populations.

Of the estimated 3 000 elephants that roamed the Cape floristic region in pre-colonial times, only 30-50 individuals remained by the early 1900s. They had taken refuge in the Knysna Forests.

By the time of the proclamation of Addo Elephant National Park, in 1931, only 11 elephants remained.

An elephant proof fence was erected in 1954, which has successfully contained the elephants, and the population has since grown from generation to generation.

Elephants can cause major ecosystem changes. When confined, natural processes such as migration are no longer possible.

For conservation managers, it is important to try mimic these natural processes or to slow the population growth rates.

With the expansion of Addo, over the last two decades, elephants have been given access to areas on which they used to historically range.

Unfortunately, even with this expansion, the population is growing at an unsustainable rate for the size of the park.

In order to slow the growth rate, immunocontraception was implemented in 2013. It is non-hormonal and a
safe, effective way of reducing female fertility.

It is based on the same principles of disease prevention through vaccination. A non-cellular capsule known as the zonapellucida (ZP) surrounds all mammalian eggs.

The immunocontraceptive vaccine is produced by harvesting the zona pellucida from the ovaries of pigs (Porcine zona pellucida or “PZP”), purified and injected into the muscle of the target female elephant.

The immune system detects the PZP as foreign material and is stimulated to produce antibodies against the proteins. These antibodies attach to the sperm receptors on the ZP of her eggs and prevents fertilisation.

The cow does not fall pregnant but will continue to show an oestrous cycle. Capture or immobilisation of cows is not required for vaccination as it can be done remotely by means of marker darts that drop out soon after injection.

The dart leaves a dye mark on the animal, thereby enabling the dartsman to distinguish between vaccinated and unvaccinated animals.

At Addo, the vaccination is done from a helicopter over as short a time possible, to minimise disturbance to the population.

Alternative management strategies to create connectivity by means of corridors between protected areas is
ongoing.

Well-connected subpopulations maintain themselves by colonising empty niches, exchanging genetic material and adapting to changing environments.

One can only hope, that in the future, we will rekindle our symbiotic, symbolic and spiritual link to elephants
and have them roaming again between Knysna and Addo.

Until such time that these connections are re-established, immunocontraception will remain a humane method of elephant population control.

• Zimmermann is senior veterinarian: Veterinary Wildlife Services: Port Elizabeth South African National Parks