Rhino horns have got smaller over time as poachers target big prizes

A database of images taken from 1886 to 2019 reveals that horn measurement has steadily decreased in 5 species of rhinoceros, in all probability because of poaching

By Christa Lesté-Lasserre

Rhinoceros horns seem to have turn into considerably smaller over the previous 130 years, in all probability on account of poaching.

Hunters kill rhinos to take away their horns as trophies or as high-value commodities for conventional Chinese language and Vietnamese medicines and supplies. The culling of rhinos with the largest horns, which have the best worth, might have inspired the survival and replica of smaller-horned rhinos – an thought supported by analyses of images spanning greater than a century, says Oscar Wilson on the College of Helsinki in Finland.

“That is dangerous information for hunters clearly, however sadly it’s dangerous information for rhinos as effectively, as a result of if the hunters need the identical quantity of horn, they’re going to must shoot extra rhinos,” he says.

As a result of rhino horns are so precious, even museum specimens are stored tightly locked away and are troublesome to entry for analysis functions. So Wilson and his colleagues analysed 80 profile-view images of residing rhinos, courting from 1886 to 2019, which rhino consultants worldwide had uploaded to the database of the Rhino Useful resource Middle, based mostly close to Cambridge, UK.

The crew used picture software program to calculate numerous anatomical measurements for every animal after which estimated its horn measurement relative to its physique measurement. As horn measurement varies significantly amongst rhino species, the crew created separate measurement charts for every of the 5 sorts of rhinoceros represented within the images: the white rhino (Ceratotherium simum), the Indian rhino (Rhinoceros unicornis), the Javan rhino (Rhinoceros sondaicus), the Sumatran rhino (Dicerorhinus sumatrensis) and the black rhino (Diceros bicornis), the final three of that are critically endangered.

A lot of the photographed rhinos had been born wild however had been residing in zoos, wildlife parks or sanctuaries on the time of the images, whereas 12 had been nonetheless residing within the wild.

Mapping out the horn sizes alongside a time chart, the researchers discovered that they had steadily decreased inside every species. Whereas the data isn’t ample to supply exact percentages of horn measurement modifications, the downward development is evident general and is most pronounced in Sumatran rhinos, says Wilson.

Poaching stress to scale back horn measurement may even have destructive results on rhinos’ behaviour and welfare, he says. “Rhinos do really use their horns for lots of various issues, like defending their territory or discovering a mate,” says Wilson. “We expect [these reductions in horn sizes] should have some impact on the way in which rhinos will stay their lives.”

Even so, the researchers’ findings “should not all doom and gloom”, he says. The crew additionally analysed 1000’s of different photographs within the database, together with creative depictions, which recommend a rising enchancment in folks’s attitudes in the direction of rhinos over the previous few centuries. “We’re viewing rhinos far more positively than we ever have,” says Wilson. “We expect that is actual trigger for optimism [concerning] rhino conservation.”

Journal reference: Folks and Nature, DOI: 10.1002/pan3.10406