A database of photos taken from 1886 to 2019 shows that the horns of five species of rhinos have gradually decreased in size, possibly due to poaching
November 1, 2022
Rhino horns appear to have gotten significantly smaller over the past 130 years, possibly as a result of poaching.
Hunters kill rhinos to remove rhino horns as trophies or high-value commodities in traditional Chinese and Vietnamese medicines and materials.Culling out the rhinos with the largest horns, which have the greatest value, may have boosted the survival and reproduction of the small-horned rhinos — a view supported by an analysis of photos spanning more than a century, says Oscar Wilson at the University of Helsinki, Finland.
“It’s obviously bad news for hunters, but unfortunately it’s also bad news for rhinos, because if hunters want the same amount of horn, they’re going to have to shoot more rhinos,” he said.
Because rhino horns are so precious, even museum specimens are tightly locked and difficult to use for research purposes.So Wilson and his colleagues analyzed 80 profile photos of live rhinos, dating from 1886 to 2019, that rhino experts around the world have uploaded to Rhino Resource Centerlocated near Cambridge, UK.
The team used imaging software to calculate various anatomical measurements of each animal and then estimated the size of its horns relative to its body size. Because horn sizes vary widely between rhino species, the team created separate size charts for each of the five rhinos represented in the photo: the white rhino (staghorn), Indian rhino (one-horned rhino), Javan rhino (rhino), Sumatran rhino (Sumatran Rhino) and the black rhino (Double Gladiator), the last three of which are critically endangered.
Most of the rhinos photographed were born wild but were living in zoos, safari parks or reserves when the photos were taken, while 12 are still living in the wild.
The researchers plotted the size of the horns along the timeline and found that they gradually decreased in each species. While this information isn’t enough to provide a precise percentage of horn size change, the decline is clear overall, and most pronounced in Sumatran rhinos, Wilson said.
Poaching pressure to reduce rhino horn size could also have a negative impact on rhino behavior and welfare, he said. “Rhinos do use their horns for a lot of different things, like defending their territory or finding mates,” Wilson said. “We believe that [these reductions in horn sizes] There must be some impact on the rhino lifestyle. “
Even so, the researchers’ findings “are not all doom and gloom,” he said. The team also analyzed thousands of other images in the database, including artistic depictions, which suggest that attitudes toward rhinos have been improving over the centuries. “We’re looking at rhinos more positively than ever before,” Wilson said. “We think that’s the real reason for optimism [concerning] Rhino conservation. “
Journal references: Human and Nature, DOI: 10.1002/pan3.10406
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