Seldom does a quest for a scientific pursuit present itself on weekend emails. And yet this is how the long route to the discovery of the Vietnamese crocodile lizard (Shinisaurus crocodilurus vietnamensis) commenced. Professor Dr Thomas Ziegler was checking his inbox one fine day at home in Bonn, Germany in 2002, and stopped on an email from Dr Le Khac Quyet. The Vietnamese primatologist had sent him a picture of a lizard he had recently photographed during a forest excursion in northern Vietnam, and sought his help in determining the creature. "That was a very exciting moment," recalls Prof Ziegler, coordinator of Cologne Zoo's biodiversity and nature conservation projects in Vietnam and Laos. "It was clear from the beginning that the picture he had sent showed a crocodile lizard."Yes, you read that right. A crocodile lizard. In Vietnam. The very discovery of the crocodile lizard (Shinisaurus crocodilurus) itself is a bit of a sensation, says Prof Ziegler. It was in 1930 that German zoologist Ernst Ahl, having examined a reptile collection from south China donated to Berlin's Zoological Museum, first offered a scientific description of a crocodile lizard. With a maximum length of 45cm, crocodile lizards are distinctly smaller than crocodiles, says Prof Ziegler. Besides, the snout of the crocodile lizard is rather blunt, but its muscular tail, with two rows of enlarged scales on the back, is similar to the tail of crocodiles. "Not only did it reveal to be a new species to science, but it was also the discovery of a new genus (Shinisaurus) and a new family (Shinisauridae) due to its striking morphological features," says Prof Ziegler. "The crocodile-like tail was eponymous for the vernacular name crocodile lizard."The crocodile lizard is closely related to monitor lizards that are also found in India, even though monitor lizards belong to another genus i.e. Varanus. While fossil evidence demonstrates that the crocodile lizard once enjoyed wide distribution, with relatives known from North America and Europe, the crocodile lizard is now only known to inhabit a few sites in southern China. This is why Prof Ziegler remarks that Dr Le Khac Quyet's photograph, which he first saw on his computer screen, forms the first country record of the crocodile lizard for Vietnam. The two reported the discovery in a scientific paper in 2003.

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A new territory

Once its presence in Vietnam was established, the crocodile lizard threw up new questions. Prof Ziegler and his partners, Hanoi-based Associate Prof Dr Truong Quang Nguyen from the Institute of Ecology and Biological Resources (IEBR), and Dr Tao Thien Nguyen, from the Vietnam National Museum of Nature (VNMN), conducted diverse excursions to learn more about the crocodile lizards in the wild in Vietnam. They further doubted that the crocodile lizards found in Vietnam were the same species as the ones found in China. "We expected to find morphological differences between the Chinese and Vietnamese crocodile lizards," says Prof Ziegler in an email interaction, "considering the new finding from Vietnam was geographically distant from the previously known populations from China. In addition, the mountain ranges in between might have caused longer separation of the populations in the different countries."But any such assertion would have to be based on further sightings and studies. It took Prof Ziegler and his team more than a decade to establish the Vietnamese crocodile lizard (Shinisaurus crocodilurus vietnamensis) as a subspecies. This is largely because these reptiles are adapted to aquatic freshwater habitats and sighting one, far less studying one scientifically, is tricky. "They inhabit vegetated streams within intact and remote evergreen, broadleaf forest. The lizards can be found on branches that overhang the water," says the 47-year- old. "It is not easy to detect crocodile lizards in the field, as you have to climb cascades and walk through in steep and slippery streams in remote forest. Because you have to be careful not to fall, you must struggle through the dense forest where the lizards are well camouflaged. Once disturbed, they escape into the water."Examining many more crocodile lizard individuals and performing genetic tests then was crucial for the team to find answers to their questions. Thanks to field research and data collection in northern Vietnam by then doctoral students Mona van Schingen and Cuong The Pham, the team was able to document the morphology i.e. form and structure, of a large number of individuals before they were released. "In the meantime, an extensive, genetic dataset too became available, and formed the basis for improved genetic results by our team geneticist Associate professor Dr Minh D. Le from the Vietnam National University (VNU), Hanoi," says Prof Ziegler, who has been studying Vietnam's herpetofauna for more than two decades.

A distinct population

Molecular and morphological differences help scientists establish creatures as distinct species. In lizards, explains Prof Ziegler, scientists study colour pattern, size and scalation i.e. the arrangement, number and shape of the scales. "We also always try to combine such data with molecular analyses to learn more about the genetic distance between populations or species," he says.No or low morphological and molecular differences between individuals argue for individuals of the same population or species while distinct differences would point to separation processes and thus different species status. If scientists are uncertain about specific status of differentiating populations, the more cautious decision is to describe a subspecies, which indicates that a separation process has started but is not yet fully complete. This is the case with the Vietnamese crocodile lizard for although Prof Ziegler's team found differences between the Chinese and Vietnamese populations, these are subtle and not easily discernible, particularly for the layman. For instance, the Chinese and Vietnamese populations differ in shape and form i.e. they exhibit different ratios of body measurements and differences in head shape, with the Vietnamese crocodile lizard sporting a more pointed snout than its Chinese counterpart. The two also differ genetically and in their ecological adaptation.

On the Red List

A December 2017 report by conservation group WWF estimated that there are only about 200 Vietnamese crocodile lizards remaining in the wild. Their diminished population is threatened by habitat destruction, coal mining and collection for the international pet trade, says Prof Ziegler. "We have been able to generate data over the past years that have helped to include the species, for the first time, on the IUCN Red List in 2014 (as Endangered). This then formed the basis to elevate it, in 2016, to Appendix I of the Convention on International Trade in Endangered Species (CITES) – an international agreement between governments that ensures international trade in specimens doesn't threaten their survival."In a scientific paper, Prof Ziegler's team recently called for developing corridors to connect existing reserves and create a new reserve for a just recently discovered, so far overlooked population in the northern part of the country. The Cologne Zoo and the IEBR's Melinh Station for Biodiversity are also working towards a conservation breeding program for the threatened Vietnamese crocodile lizard for creation of an insurance population for future release. "Our team has also developed a cartoon character, Shini, to explain to school students how important the crocodile lizards - and biodiversity in general - as well as their conservation are."

The Rare Reptile

Vietnamese crocodile lizard (Shinisaurus crocodilurus vietnamensis)

  • Vietnamese crocodile lizard is a subspecies of the Crocodile lizard
  • Not more than 45cm in length, the Vietnamese crocodile lizard is found on branches that hang over vegetated streams in evergreen, broadleaf forests.
  • Their muscular tails make them perfect swimmers and divers. If disturbed, the Vietnamese crocodile lizard will disappear in water.
  • They feed on a variety of invertebrate prey, such as worms and insects.
  • The crocodile lizard gives birth to living young inside the water. This takes place once a year and the clutch size comprises two to 12 offspring.