The rhinoceros horn is getting smaller and smaller

The rhino’s horns are getting smaller and smaller, according to these researchers, the animals owe this to intensive poaching.

An international team of researchers has collected centuries of images of rhinos. From this they conclude that poaching has permanently changed the appearance of the rhinoceros. In the scientific journal People and Nature they report on how and why.

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Rhinoceros in art

More than 4,000 images were collected for the study, dating from 1481 to 2021. All depict one of five species of rhinoceros. The historical prints are not really reliable – the proportions and dimensions do not always correspond to reality. However, they can provide the first indication of changes in the rhino’s appearance.

From the 16e century, for example, the horn-to-body ratio in artwork steadily declined, the researchers noted. This does not necessarily mean that the horns actually became shorter. Artists copy each other – especially when it comes to exotic animals like rhinos. So: harder evidence was needed.

Survival of the smallest

Therefore, the team also collected images. The final photo collection consisted of 80 images, with the first photo from 1886 and the last from 2018. In fact, every rhinoceros species with an increasingly shorter horn has been photographed in the past century. The researchers suspect that this phenomenon is due to intensive poaching. Over time, poachers killed off the rhinos with the largest horns, leaving especially those with smaller horns to survive and reproduce.

In some African elephants, the demand for ivory has created a similar selection pressure. The gene that determines whether an elephant does not develop tusks is now more common than before, in both African and Asian elephants.

While shorter tusks and horns protect animals from poachers, they are not very useful. Rhinos evolved their horns for a reason – different species use them in different ways, for example to grab food or defend against predators. Rhinos with smaller horns have a lower chance of survival,” explains one of the researchers, Oscar Wilson.

Theodore Roosevelt with a rhinoceros


Since 2007, poaching and illegal trade in rhino horn has increased. This is partly due to the increasing demand for ivory in traditional Asian medicine, but also to the severe economic inequality in countries in Africa and Asia, such as South Africa.

Bram Büscher, professor of political ecology at Wageningen, told Trouw that there are people living around the South African safari parks who live on less than $3 a day. The horns now yield more than gold and cocaine and therefore provide a chance for survival for many.

In game parks and nature reserves where rhinos occur, everything is done to preserve the animals. For example, there is cooperation with the army, but also with the human inhabitants or residents of the parks. Rosaleen Duffy, professor of international politics at the University of Sheffield, calls it a ‘war for biodiversity’: “With both sides being drawn into an arms race and a conflict that is increasingly claiming human lives.” Rangers killed an average of two poachers a month in Kazaringa Natural Park in northern India in 2015. That year, more people than rhinos were shot in the park.

Today, all rhino species are threatened by habitat loss and hunting. Of the white rhinoceros, the northern subspecies now consists of only two female individuals. The only way to have additional offspring is through artificial insemination with frozen sperm. Of the 500,000 rhinos in the early 20se century, there are now around 26,000 left.

Sources: Humans and Nature, Science Alert, Trouw
Picture: Pixabay

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