According to Dr Audrey Delsink, executive director of Humane Society International/Africa (HSI/Africa), this provided an effective alternative to the traditional method of culling, in which case entire family groups were destroyed. HSI/Africa had treated some 1 600 elephant cows from 2000 until August 2023.
“This unique programme helps to manage African elephant populations using porcine zona pellucida (pZP) immunocontraception. It is a reversible, proactive and humane population management tool that can reduce or stabilise elephant growth rates within the scope of management objectives and carrying capacities of a specific area,” she said.
While the African elephant was an endangered species overall, the animals could become overpopulated in specific areas due to being fenced in, amongst other reasons. Lethal management tools, such as culling or hunting, were often used to control elephant population numbers, permanently removing herds or bulls and their genetic contribution.
The pZP immunocontraception used the female elephant’s own immune response to block egg fertilisation. Female elephants over the age of 10 years old were treated remotely from a helicopter with a dart that contained the immunocontraception vaccine.
A purple marking substance was sprayed onto the elephant at the dart site for a quick reference as to which animals had already been darted. As the needle was not barbed, the dart fell out shortly afterwards, causing minimal discomfort to the elephant cow. The animals did not need to be immobilised to be treated and vaccinations were completed within minutes.
“Shooting these magnificent animals to control their numbers is an unnecessary way to deal with elephant population growth for herds that are increasingly squeezed into smaller pockets by human encroachment. Immunocontraception is the future of humane elephant conservation,” Delsink added.
She pointed out that elephant cows were only vaccinated after they had given birth to at least one calf.
This was done specifically for the social well-being of the cow and the herd, as elephants were highly sociable animals. The pZP immunocontraception did not affect any phase of an elephant cow’s pregnancy. If a cow was already pregnant at the time of the first treatment, she would still carry to term and deliver the calf.