Hello,
I´m a PhD student at the Museum of Zoology in Dresden, Germany and I´m working on Natrix natrix. My focus is on genetic studies about population genetics and also a possible taxonomic revision of this species. Many samples have been collected yet but there are still needed more - especially from France, Switzerland and also from the contact zone of "helvetica/natrix" in the Rhine region. However, samples from Spain, the Balkan peninsula, Eastern or Northern Europe are also needed. So, if you find a shed skin or a dead specimen it would be great if you could collect it, store it cool and contact me for sending (dead specimens: a piece of tissue is sufficient).
Many thanks!