Hunting caused rhino horns to shrink in last century, University of Cambridge researchers believe
University of Cambridge researchers have found rhinoceros horns have gradually decreased in size over time and believed that intensive hunting may be responsible.
They measured the horns of 80 rhinos in photographs taken in profile view between 1886 and 2018.
The images, held by an online repository, the Rhino Resource Centre, covered all five species of rhino - white, black, Indian, Javan and Sumatran - and horn length was found to have decreased significantly in all species.
Rhino horns command a high price and are in demand as a financial investment and for use in traditional medicines in China and Vietnam.
Hunters have cause severed declines in rhino populations and the researchers believe that their tendency to shoot rhinos with the longest horns has left smaller-horned survivors. As they reproduce, they pass on their traits for smaller horns to future generations.
This has never been shown before in rhinos, although it has in other animals.
Oscar Wilson, formerly a researcher in the University of Cambridge’s Department of Zoology, first author of the report, said: “We were really excited that we could find evidence from photographs that rhino horns have become shorter over time. They’re probably one of the hardest things to work on in natural history because of the security concerns.”
Oscar, now based at the University of Helsinki, Finland, added: “Rhinos evolved their horns for a reason - different species use them in different ways such as helping to grasp food or to defend against predators - so we think that having smaller horns will be detrimental to their survival.”
The researchers measured other body parts, such as body and head length, to accurately work out the horn length in proportion to their body size.
They also analysed drawings and photographs made over 500 years and found a dramatic shift in human perceptions of rhinos around 1950, when the animals became the focus of conservation efforts rather than hunting.
Dr Ed Turner, at the University’s Department of Zoology, senior author of the report published in the journal People and Nature, said: “We found that we can use images from the last few centuries to visualise how human attitudes towards wildlife have changed, and how artists have influenced these views.”
There are hundreds of photos from the late 19th and early 20th centuries showing rhinos shot dead by hunters, including a 1911 photograph of US President Theodore Roosevelt standing triumphantly over a black rhino he had just killed.
Other early images, showing rhinos as huge, frightening animals chasing humans, may have helped justify hunting them.
In the 1950s, when European empires collapsed and African countries became independent, meaning European hunters no longer had easy access to Africa for hunting, there was a sudden shift from hunting to efforts to keep them alive.
“For at least a few decades now there’s been much more of a focus on the conservation of rhinos – and this is reflected in the more recent images, which relate to their conservation in sanctuaries or their plight in the wild,” added Oscar.
More than 5,000 illustrations and photographs of rhinos are held by The Rhino Resource Centre, drawn from extensive archival research and submissions from rhino experts. The artwork covers more than 500 years, while the photographs date back 150 years.
