Imperial College London

Meet the weird reptiles at the short end of the evolutionary stick

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Green-haired turtle. Credit: Chris Van Wyk

Mary river turtle

Turtles that breathe through their genitals and tiny chameleons are amongst the weird reptiles heading for extinction unless urgent action is taken.

International conservation charity ZSL’s (Zoological Society of London) pioneering EDGE of Existence programme highlight 100 species that are endangered but also evolutionarily unique, defining them as priorities for conservation efforts.

Reptiles often receive the short end of the stick in conservation terms, compared with the likes of birds and mammals. However, the EDGE Reptile List highlights just how unique, vulnerable and amazing these creatures really are. Rikki Gumbs

Backed by a study published in journal PLOS ONE, including Imperial authors, ZSL’s EDGE Reptiles ranks the top conservation priorities for a class of animals that includes turtles, crocodilians, snakes and lizards.

The list is unique in not only considering extinction threat, but also how evolutionarily unique a species is. Many of the species effectively represent their own distinct branches of the Tree of Life, meaning they broke away from similar species a long time ago, and have no close relatives.

The list uses a complex formula to highlight species that are particularly Evolutionarily Distinct and Globally Endangered (EDGE), providing wildlife scientists worldwide with a scientifically rigorous way of focusing their conservation efforts.

Iconic species featuring on ZSL’s EDGE Reptiles List include the world’s largest sea turtle, the leatherback (Dermochelys coriacea) which weighs in at number 85, and the Mary River turtle (Elusor macrurus), which can stay underwater for up to three days by breathing through its reproductive organs and sits at number 30.

  • Gharial

    A gharial, #16 on the list. Credit: Josh More

  • Leatherback turtle

    A leatherback turtle, #85 on the list. Credit: Hans Hillewaert

  • Madagascan big-headed turtle

    Madagascan big-headed turtle, #1 on the list. Credit: Bill Hughes

  • Madagascar blind snake

    Madagascar blind snake, #3 on the list. Credit: Jörn Köhler

  • Roti Island snake-necked turtle

    Roti Island snake-necked turtle, #6 on the list. Credit: Daniel Kane

  • Round Island keel-scaled boa

    Round Island keel-scaled boa, #26 on the list. Credit: Nick Page

EDGE Reptiles co-ordinator Rikki Gumbs led the PLOS ONE paper as part of his PhD studies at ZSL and Imperial College London’s Science and Solutions for a Changing Planet (SSCP) Doctoral Training Partnership. He said: “Reptiles often receive the short end of the stick in conservation terms, compared with the likes of birds and mammals.

"However, the EDGE Reptile List highlights just how unique, vulnerable and amazing these creatures really are. From the world’s largest sea turtles to a blind species of snake found only in Madagascar, the diversity of EDGE Reptiles is breath-taking.”

High on the list

Topping the list overall, with an EDGE score higher than that of any amphibian, bird or mammal, is the Madagascan big-headed turtle (Erymnochelys madagascariensis), while various geckos, chameleons and snakes also feature, including the Round Island keel-scaled boa (Casarea dussumieri), ranked number 23 on the list.

This strange species, whose closest relative on the Tree of Life was declared extinct less than 30 years ago, can change colour over a 24-hour period and is also the only vertebrate with a joint in its upper jaw, used to capture and eat its lizard prey.

Gumbs adds: “Just as with tigers, rhinos and elephants, it is vital we do our utmost to save these unique and too often overlooked animals. Many EDGE Reptiles are the sole survivors of ancient lineages, whose branches of the Tree of Life stretch back to the age of the dinosaurs. If we lose these species there will be nothing like them left on Earth.

“Using ZSL’s EDGE methodology to create the world’s first EDGE Reptile List, not only are we providing conservation scientists with a quantitative tool to prioritise species for conservation, but we also hope to bring the plight of these weird and wonderful creatures to the public’s attention before they disappear.” 

Empowering a new generation

Commenting on the publication of the EDGE Reptiles ranking, ZSL’s EDGE of Existence Programme Manager Dr Nisha Owen said: “When EDGE launched in 2007, our vision was to shine a light on those species that, if they were allowed to go extinct, would effectively take an entire branch of the Tree of Life with them.

"Over the intervening decade, our EDGE Fellows have worked to save everything from pangolins and echidnas, to the Chinese giant salamander and Philippine Eagle.

“We’re delighted to now be expanding the programme to embrace reptiles as well, highlighting a whole additional class of evolutionarily distinct and globally endangered wildlife while also empowering a new generation of field conservationists striving worldwide to secure their protection.”

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Tetrapods on the EDGE: Overcoming data limitations to identify phylogenetic conservation priorities’ by Rikki Gumbs, Claudia L. Gray, Oliver R. Wearn, Nisha R. Owen is published in PLOS ONE.

See the press release of this article

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Hayley Dunning
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