“Rhinos use their horns, so losing them probably not going to be good for them,” he said. While the impact of the shrinkage is not known, Wilson said it could be detrimental. That, he said, suggests the decrease in horn length likely reflects selection pressures that the animals face in their natural habitat, although the researchers are now carrying out further work with wild populations to explore whether the same trend is seen. While 65 of the rhinos photographed were in captivity, Wilson noted that the majority came either directly from the wild, or were born to rhinos who had previously lived in the wild. However, for all five species of rhino, the relative length of the horn has decreased over time. The results reveal that, relative to their body length, black and white rhinos had the longest horns, while Sumatran rhinos had the shortest. As a result, the team were able to explore whether the relative size of rhino horns got larger or smaller over time with respect to the average ratio. They then calculated the length of the horn relative to that of the animal’s body before taking an average of these values and calculating the difference compared with the ratio seen for each particular image. The team focused on 80 photographs of rhinos that show the creatures side on. For centuries, rhino horn has been used in traditional Chinese medicine (TCM) to treat a wide variety of illnesses ranging from reducing fevers to stopping nosebleeds and preventing strokes. The anterior front horn starts to grow first followed by the posterior horn from about. Some of the art dates back to the 15th century. Calves of all rhino species are born without horns. They made their discovery by examining artwork and photographs of rhinos held by the Rhino Resource Center (RRC) in Utrecht. “Preferential hunting selection for individuals with larger horns or tusks resulted in individuals with smaller features surviving and reproducing more, passing on these traits to future generations, and resulting in an evolutionary change,” the researchers write in the journal People and Nature. Wilson and colleagues say a study of archive images of the animals suggests the size of a rhino’s horn, relative to its body length, has decreased over time.Ī similar trend has been recorded for creatures such as elephants and wild sheep. “In the case of rhinos, people basically have always wanted the largest horn,” said Oscar Wilson, a doctoral student and first author of the research at the University of Helsinki, adding that bigger horns will fetch modern poachers a higher price. Rhinoceros horn has been used medicinally and as a talisman in many cultures and animals are slaughtered to obtain the horn.
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