Rhinoceros horns have shrunk steadily over the last century, and scientists believe it is due to hunting.
The study, published in the journal People And Nature, is based on an analysis of thousands of photos of animals taken over the last 140 years.
According to University of Cambridge experts, rhino horns are frequently trophy hunted or used in medicines in China and Vietnam.
After years of hunting rhinos with the longest horns, researchers believe rhinos with smaller horns are more likely to survive and pass on their genes to future generations.
“We were really excited that we could find evidence from photographs that rhino horns have become shorter over time,” Oscar Wilson, lead author of the report and a former researcher with the University of Cambridge’s zoology department, said. Because of security concerns, they’re probably one of the most difficult things to work on in natural history.”
“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,” said Mr. Wilson, who is now based at the University of Helsinki in Finland.
The researchers measured the horns of 80 rhinos photographed between 1886 and 2018, representing all five species (white, black, Indian, Javan, and Sumatran) in The Rhino Resource Centre’s online archive.
They scrutinised photographs of rhinos killed by hunters, including one of former US President Theodore Roosevelt standing over a black rhino he had just killed in 1911.
The researchers measured the horns of 80 rhinos photographed between 1886 and 2018, representing all five species (white, black, Indian, Javan, and Sumatran) in The Rhino Resource Centre’s online archive.
They scrutinized photographs of rhinos killed by hunters, including one of former US President Theodore Roosevelt standing over a black rhino he had just killed in 1911.
“For at least a few decades now, there’s been a much greater emphasis on rhino conservation – and this is reflected in the more recent images, which relate to their conservation in sanctuaries or their plight in the wild,” Mr Wilson said.
The rhinoceros is an endangered species, with fewer than 30,000 remaining in the wild today, compared to over 500,000 at the turn of the twentieth century.
Black, Javan, and Sumatran rhinos are critically endangered.
