Is rhino horn-trimming causing more damage than good?

The rhinoceros is a mega-herbivore teetering on the verge of extinction due to rampant hunting for its horn, which is highly valued, particularly in traditional medicine practices throughout Asia. As a result, wildlife conservationists have been searching high and low for ways to protect this highly endangered species from poachers.

In 1989, conservationists in Namibia began trials for rhino horn trimming, also known as dehorning. This surgical procedure involves sedating the rhino and partially removing its horn with precision, leaving the growing point of the horn untouched while significantly reducing the remnant horn stump. The aim is to reduce the incentive for poachers to kill the animal.

The initial trial of horn trimming in Namibia appeared to be a success, with no poaching incidents reported among horn-trimmed rhinos. As a result, this approach was adopted as an essential anti-poaching strategy in several other countries, including South Africa, Zimbabwe, Botswana, and Kenya. But while horn trimming has been effective in some areas, poachers have continued to target rhinos regardless of whether or not they have been trimmed in other locations.

This is because horn trimming does not completely remove the horn, which would be fatal to the animal, and some poachers are prepared to kill a rhino for the stump.

Africa-based conservationists have therefore incorporated humane horn trimming as one part of a holistic anti-poaching strategy that includes security, monitoring and education.

'cryptic but powerful population-level consequences'

Despite nearly three decades of active rhino horn trimming, a recent study by a team of international researchers suggests that this approach could be having unintended consequences on the social behaviour of rhinos. The study, conducted over a 15-year period in nearly a dozen game reserves in South Africa, found that "dehorning" could have "cryptic but powerful population-level consequences."

According to the research findings, horn-trimmed black rhinos may become less confident, which can lead to changes in their home territories and social interaction habits. These changes may ultimately affect breeding habits and other behaviours.

In their findings, which were published in Proceedings of the National Academy of Sciences in June, the 14 researchers concluded that horn-trimming could have potential negative effects on rhino populations and advised caution in the use of the procedure while more comprehensive research into the practice is being conducted.

"By proactively dehorning entire rhinoceros populations, conservationists aim to deter poaching and prevent species loss. However, such conservation interventions may have hidden and underestimated effects on animals’ behaviour and ecology," the study reads.

The research findings were based on data collected over a period of approximately 15 years, during which black rhinos were monitored across 10 game reserves in South Africa. The study included approximately 24,000 sightings of 368 individuals to determine the impact of horn-trimming on the space usage and social interactions of black rhinos.

"While preventative dehorning at these reserves coincided with a nationwide decrease in black rhino mortality from poaching and did not infer increased natural mortality, dehorned black rhinos decreased their home range area by, on average, 11.7 km2  (45.5%) and were 37% less likely to engage in social encounters," the study reads. "We conclude that dehorning black rhinos as an anti-poaching measure alters their behavioural ecology, although the potential population-level effects of these changes remain to be determined."

The researchers noted that the significant impacts of horn-trimming on the behavioural ecology of black rhinos could have demographic consequences, the full extent of which is still unknown. They further emphasised the need for considering behavioural responses when evaluating the overall benefit of conservation interventions.

Research Findings Welcome, But sceptisism remains

Kevin Leo-Smith, a board member of Rhino Revolution, a South Africa-based rhino conservation initiative, said that while they welcome the study's findings, more research is necessary to obtain conclusive results.

"While research using meta studies are an important and an essential part of all conservation science analyses, there are important cautions around extrapolation of this data to all situations," Leo-Smith told FairPlanet.

"An essential part of the natural sciences are the studies of a population of a species in a specific environment. Consequently, these results are really only reliable for that situation and extrapolations are dangerous, unless corroborated in identical studies on the same species in different environments."

"Therefore," he added, "we also need to understand the constraints of this meta study, as each separate study may not have asked the same question that this meta study attempts to answer. This does not in any way negate the conclusions and suggestions for further investigations of the meta study."

Leo-Smith pointed out that if social interactions and home ranges were measured more objectively, the results of the study could be different. However, he noted that to make such an assessment, rhinos would have to be fitted with GPS ankle collars that provide high-frequency location measurements.

"The high frequency is needed as many black rhino social interactions are of short duration [in his personal opinion, he highlighted], [and often] take place at night, when black rhinos congregate at water holes.

"We would only conclusively know a specific home range extent if location measurements are done at least hourly for an entire year to cover seasonal effects. But the batteries of these ankle collars are quickly depleted by hourly recording regimes - so these studies are challenging and expensive to do."

He added that Rhino Revolution remains of the "unresearched opinion" that horn trimming is consequential for the survival of black rhinos, a highly endangered species. 

"Empirical evidence indicates that it reduces the poaching incentive and, therefore, the threat to these trimmed rhinos. Rhino Revolution will continue to sponsor and promote horn trimming for both rhino species in South Africa until and unless negative reproductive or other population level impacts are proven in future research or through observation on trimmed populations.

He further said that Rhino Revolution will not support increasing stocking rates on trimmed reserves as a result of the reduction in home ranges, citing the need for better information regarding the impact of horn-trimming on rhino populations. 

Horn Trimming: ‘Unnatural’ But Necessary

Megan Carr, founder of Rhinos in Africa, a rhino think tank, told FairPlanet that rhino horn-trimming should be understood as part of the attempt to save an endangered animal from extinction.

"The practice of dehorning of rhino is unnatural, but we understand and sympathise with the fact that it is a desperate attempt to save the rhino lives," Carr told FairPlanet. 

Part of the conservation strategy is education, which involves debunking the myth about the supposed medicinal properties found in a rhino horn. Carr emphasised that the stockpiling of trimmed horns creates a false impression that the horn has value, perpetuating the demand for rhino horn products.

"We believe that to reduce the value of the rhino horn, the horn should be destroyed," she wrote. "Until rhino horn is declared valueless the killing and illegal trade will continue."

Conservation Africa, another wildlife protection non-profit, maintains that rhino horn trimming remains an effective anti-poaching strategy, despite its downsides. These include recurrent costs (averaging USD 2,000 per trim) as the horns grow back, the risk of harm or death during the surgical procedure, and the ethical question of whether it is right to remove a rhino's horn. Rhinos use their horns to protect their young and engage in territorial battles, particularly between males.

"Despite these drawbacks, most wildlife conservationists working with rhino agree that, until a better strategy is found, the benefits of horn trimming greatly outweigh the risks," the lobby says.

Image by Beks.