How Human‑led Poaching and Hunting Have Altered Rhinoceros Horns
The relentless poaching of rhinoceros for their horns seems to have affected change in their physical appearance, suggests a new study published in the journal People and Nature in September.
The study analyzed photographs of rhinos from the repository of the Rhino Resource Centre in The Netherlands. Photographs of all five existing species of the giant mammal taken between 1886 and 2018 were considered for the study. Researchers, on analyzing these photographs, noticed the length of the horn in all five species of rhinoceros had significantly declined over the decades. Scientists speculate that this decline in length was brought about by the frequent poaching and hunting of rhinos.
Rhino hunting is a widespread menace in all the regions where they are found. At the beginning of the 20th century, the global rhino population was above 5,00,000 animals. In 2020, less than 30,000 of them remained in the wild. Of the five extant species of the giant mammal, three are identified by the International Union of Conservation of Nature (IUCN) as “critically endangered,” with only a few handfuls surviving in all three of these species. Of the other two, the white rhino is recognized as “near threatened” while the greater one-horned rhino is listed as “vulnerable.” It is important to note here that this drop in numbers is almost entirely attributable to humans. As the African Wildlife Foundation notes, “In the wild, the adult… rhino has no predators except for humans.”
Rhino horns are a prized possession in some Asian societies, most notably in China and Vietnam, where the horn is coveted both as medicine and a status symbol. Rhino horns are also popular in Yemen, where a market for rhino horns as dagger holders thrived legally in the 1970s and 1980s. In the present day, the trade has moved to the black market in the face of international sanctions on the horn trade. In Vietnam, the powdered horn is believed to be a cure for hangovers. They also signify status and wealth. The illegal trade of horns between southern Africa and Vietnam is worth millions of dollars. Given the deep connection the horns have with tradition and status, it is unlikely that their commercial value will go down any time soon.
In fact, documentation of self-admitted rhino horn buyers reflects that people often have little concern about the dwindling rhino population that is caused by relentless hunting. “The killing of rhinos in Africa was seen as a remote issue, something that happened far away, out of their influence because they didn’t kill the rhinos themselves,” a Down To Earth report from 2019 noted.
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On one hand, rhino populations have rapidly dwindled due to hunting. On the other, rhinos that have managed to survive seem to have adapted in the hopes of deflecting poachers. The researchers write that they “found a small but significant decline in relative horn length over time across all species. These results could be indicative of directional selection in response to hunting pressures.”
They also suggest that the increasing shooting of rhinos with longer horns has resulted in more and more of the short-horned members of the species surviving. Since they reproduced in larger numbers over the years, horns have, overall, shrunk by a great deal in the last several years. While this is the first time such a change has been noted in the rhinoceros, animal bodies adapting to deflect human interference is not a new phenomenon in itself.
For instance, as Saumya Kalia wrote in The Swaddle in 2021, some female African elephants are evolving without tusks in Africa to prevent ivory poaching. “Researchers found the number of tuskless female elephants in Mozambique increased by almost double over 30 years. This overlaps with a period of civil conflict, where armed forces slaughtered 90% of the elephant population to produce ivory. This ivory went on to finance the conflict” Researchers in the current study speculate that the rhinos may be exhibiting similar adaptive evolution. However, this is concerning as in both elephants and rhinoceros, the tusks and horns serve important functions for the animals.
While in elephants the tusks help them “dig, gather food, strip bark from trees to eat, and defend,” the researchers mention that in different species of rhinos the horns serve different purposes. “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,” they cautioned in a press release.
The study highlights the extent to which human interference with wildlife can not only endanger animal populations but also change their bodies — compromising features that were developed for protection and adaptability in the wild in favor of protection from human interference. This is a worrying symptom of thoughtless and relentless human consumption and is a signal that conservation efforts need to be strengthened urgently, and strict action must be taken against the illegal horn trade.