Discoveries

November 18, 2022

The Big Shrink

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Hunters kill rhinoceros for their horns, either for trophies or as high-value commodities used in traditional Chinese and Vietnamese medicine.

But rhino poaching hasn’t only threatened the mammals’ lives. It has also changed the size of their horns, Sky News reported.

In a new study, scientists found that the horns of all five surviving rhino species have shrunk over the past 140 years.

Researchers analyzed 80 photographs of rhinos dating from 1886 to 2019, including one showing former US President Theodore Roosevelt standing over a black rhino he had just killed in 1911.

They used imaging software to determine numerous anatomical measurements for each animal and then assessed the size of its horn in relation to its body size.

Their findings showed that the horn sizes within each species had gradually decreased over time.

The team suggested that the shrinking was prompted by hunting, noting that many hunters would go after rhinos with larger horns. Consequently, this allowed the ones with smaller horns to survive and pass their short-horn genes to future generations.

But lead author Oscar Wilson told New Scientist that this big shrink is still bad news for the large animals because hunters will then “have to shoot more rhinos.”

He added that this reduction can also impact the well-being of rhinos because the horns are used for a variety of things, including defending territory and finding mates.

Still, he added that his colleagues also studied thousands of other images – including artistic depictions – that hint that people have developed a more positive attitude toward the big-horned mammal.

“We’re viewing rhinos way more positively than we ever have,” he noted. “We think this is real cause for optimism (concerning) rhino conservation.”

This story originally appeared in the November 18, 2022 newsletter, Waving Bye-Bye.