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Genomic study of the rhinoceros family tree could help to save the critically endangered animals from going extinct © Beth Zaiken

Study of rhino's family tree could help save them from extinction

Published: 24th August, 2021 at 16:00

Rhinoceroses naturally have low genetic diversity. This means we may be able to recover their numbers despite there only being a few of them left, the researchers say.

There are currently five species of rhinoceros living on the Earth - Indian, Javan, Sumatran, white and black. But piecing together exactly how they are related has proven problematic thanks to a lack of genetic data.

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Now, a study by an international team of researchers has helped to fill the gaps in the rhino evolutionary family tree by analysing and comparing the genomes of all five living species along with the genomes of three extinct species - woolly, Merck’s, and the Siberian Unicorn.

“We can now show that the main branch in the rhinoceroses’ tree of life is among geographic regions, Africa versus Eurasia, and not between the rhinos that have one versus two horns,” said study author Prof Love Dalen of the Centre for Palaeogenetics and the Swedish Museum of Natural History.

“The second important finding is that all rhinoceroses, even the extinct ones, have comparatively low genetic diversity. To some extent, this means that the low genetic diversity we see in present-day rhinos, which are all endangered, is partly a consequence of their biology.”

Read more about rhino conservation:

They found that all eight species showed a slow decrease in population size over the past two million years or had consistently small populations over extended periods of time – this may mean that rhinoceroses are naturally adapted to living in groups with low genetic diversity, the researchers say.

This theory fits with the currently held idea that rhino populations have not accumulated disease-causing genetic mutations over the past 100 years, allowing them to stay healthy despite inbreeding and low genetic diversity.

The findings also mean that conservation programs designed to help rhino numbers recover should perhaps switch from focussing on increasing genetic diversity to increasing population sizes, the researchers say.

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However, rhino numbers are dwindling. According to charity Save the Rhino, there are around 5,000 black and 18,000 white rhinos remaining in Africa, 3,500 Indian rhinos, and fewer than 100 Javan and Sumatran rhinos in southeast Asian.

Reader Q&A: How does trophy hunting affect wild animal populations?

Asked by: Steven White, Bromley

Since the days of the Roman Empire, wild animals have been slaughtered to prove power and wealth. Bigger is better when it comes to this ‘sport’, which means that dominant, mature male rhinos, elephants, lions, leopards and other animals are the prime targets of hunters.

The artificially premature loss of strong, healthy individuals takes vital genes out of the breeding pool which, over time, can result in an overall decline in body size and, where applicable, also horn or tusk size.

Removing these frontline animals also undermines social cohesion and can leave members of prides and herds vulnerable to attack by other members of their own species. Although some argue that money from trophy hunting can help with conservation, there is not enough evidence to convince us that it can.

Read more:

Authors

Jason Goodyer
Jason GoodyerCommissioning editor, BBC Science Focus

Jason is the commissioning editor for BBC Science Focus. He holds an MSc in physics and was named Section Editor of the Year by the British Society of Magazine Editors in 2019. He has been reporting on science and technology for more than a decade. During this time, he's walked the tunnels of the Large Hadron Collider, watched Stephen Hawking deliver his Reith Lecture on Black Holes and reported on everything from simulation universes to dancing cockatoos. He looks after the magazine’s and website’s news sections and makes regular appearances on the Instant Genius Podcast.

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