RESEARCH: Black Rhinos lose confidence when they don’t have a horn

To protect Black Rhinos from poachers killing them for their horn, conservationalists use a strategy of de-horning. The theory is: if the Black Rhino has no horn, then poachers won’t kill it, and the rhino lives longer. Rhino horns are more valuable than diamonds or gold on the black market in Southeast Asia. Over the past decade in southern Africa, steps were taken to save the rhinos from being poached, maimed, and killed for their horns. 

De-horning is painless for the rhino, taking about 20 minutes. Veterinarians sedate the rhino, blindfold it, and insert earplugs, then use a chain saw to cut off the top of its horn, but only the section that does not contain nerves. When poachers cut of a rhino’s horn, they do it quickly at night, and they often damage the nerves or kill it. Rhino horns grow back, and veterinarians usually de-horn a rhino once every 18 months.

Scientists wanted to know more about rhinos that had been de-horned. New research has found some interesting results. 

Black Rhinoceros

The Black Rhinoceros (Diceros bicornis) is a mammal in the Rhinocerotidae family. It is also called the Hook-Lipped Rhinoceros. It lives in eastern and southern Africa. It is not actually black: it is grey or dark grey. 

The Black Rhino has a wide mouth, a broad body, a large head, a short neck, and stumpy legs with three toes on each foot. It has two horn-like keratin growths, one behind the other. The front horn is larger than the second horn. The front horn is about 50-140 centimetres (2 to 4.5 feet) long, which is longer than the horn of the White Rhinoceros. 

It has a pointed and prehensile upper lip, which it uses to grasp leaves and twigs from trees when feeding. Therefore, it is an herbivorous browser. The White Rhino is a grazer because it eats grass. The Black Rhino eats from trees, so it prefers habitats with thick scrub and bushland.

The Black Rhino is critically endangered. Only 5,500-6,000 individuals remain – 36% of them are in South Africa. 

New research, published on 12 June 2023 in the Proceedings of the National Academy of Sciences, and documented in the New York Times, shows that Black Rhinos that have been de-horned change their behaviour. When they have horns, they behave in their usual manner, and when they are de-horned, they behave very differently. 

De-horned Black Rhinos reduced the range in which they travel – they don’t travel very far any more. De-horned Black Rhinos reduce their interaction with other Black Rhinos – they lose confidence and become more timid and shy. 

Conservation biologist Vanessa Duthé at the University of Neuchatel in Switzerland, and her team, analysed 15 years of data and information that tracked the movements of 368 Black Rhinos across 10 South African wildlife reserves. Before 2013, none of the Black Rhinos in the study had been de-horned. By 2020, 63% of the Black Rhinos in the study had been de-horned. So, the scientists observed the data from horned and de-horned Black Rhinos to identify similarities and differences in behaviour.

Vanessa Duthé said that de-horning is ‘definitely disrupting their social networks. They are not so sure of themselves anymore. They’ve lost their main defense and their confidence.’

The de-horned Black Rhinos became more vulnerable. They lost their appetite for food, they didn’t want to explore the area around them, and they didn’t feel like engaging in conflict with other rhinos.

The scientists found that de-horning did not increase the likelihood of a Black Rhino dying from causes other than poaching. However, they reduced their exploring range by 45.5%, although this varied between individuals, depending on the size of their original territory. One male, Hamba Njalo, reduced his territory by 20%, leaving him with 2 square miles to roam. Another male, Xosha, reduced his territory by 82%, leaving him with 8.5 square miles. 

The scientists also found that de-horned individuals were 37% less likely to engage in social interactions, especially between males. So, males became shyer, and lost more confidence than females, and less aggressive.

Since conservationalists de-horned the Black Rhino, poaching decreased. In 2015, rhino poaching reached its peak of 1,349 rhinos killed out of a total of about 22,000 African Black Rhinos and White Rhinos. In 2022, about 548 Black Rhinos and White Rhinos were poached and killed. 

Scientists are debating whether to continue de-horning rhinos or not, because there are many factors involved in the decreased number of killngs, such as economic, social, and security factors affecting poaching. ‘No one has come to a conclusion yet,’ as to whether de-horning is effective or not in saving the rhinos, said Vanessa Duthé. Some scientists say that de-horning is not ideal, but a shy rhino is better than a dead rhino. 

Black Rhinoceros

Location of photographs: Ol Pejeta Conservancy, Kenya

Photographer: Martina Nicolls


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