How do you castrate an elephant? With great difficulty‚ because its testes are hidden deep within its abdomen.

However, thanks to the efforts of a team of South African veterinary scientists‚ chemical castration is now an option. Experiments on 17 African bull elephants with hormone treatment used on dogs‚ pigs‚ bulls, horses and buck found that a series of injections shrank their testes by 60%‚ and sperm production plummeted.

"Although African elephant populations are under pressure‚ in southern Africa fertility control is warranted as capacities in smaller‚ fenced game reserves are exceeded‚" said researchers from the University of Pretoria’s Onderstepoort faculty of veterinary science and the National Zoological Gardens of SA.

The testosterone-suppressing hormone treatment could also be used to deal with "problem" elephants‚ they wrote in the journal Plos One. "Wild African elephants are reportedly more likely to raid crops and break fences compared to females."

The course of injections could also have benefits for captive elephant bulls and their handlers in zoos and elephant sanctuaries. These include suppressing testosterone-driven aggression and must [a time in which bull elephants display highly aggressive behaviour accompanied by a large rise in testosterone]; avoiding prolonged separation and chaining during must; and allowing the formation of bachelor herds.

Said lead author Imke Lueders: "In captive breeding populations in Europe and North America‚ more male than female elephant calves are born. The housing and management of these excess males as they mature is a rapidly looming problem." Chemical castration could be a solution.

In the experiment‚ "before commencement of treatment‚ two of the captive bulls were highly aggressive towards their handlers and one wild bull was in full must. The aggressive behaviour and must ceased after two immunisations and did not recur by the end of the study"‚ said Lueders.

"None of the other bulls showed sexual interest‚ or must or must-related behaviour throughout the study‚ despite many being at an age where must occurs regularly or intermittently."

The researchers said the reversibility of the hormone treatment needed investigation because loss of testosterone at a young age could lead to retarded development of the penis and testes.

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