Today, despite a rainy, windy sky and a temperature at around 10°C, I went to a traditional swiss place to try to watch both N. maura and tessellata.
I was lucky enough to find 2 juveniles of both N. maura and tessellate under the stones in an area of about 4 m2 !
All individuals show, I think, the typical criteria of identification.
more pics of these ind. http://www.pbase.com/stephaubry/natrix_tessellata_220412
more pics of these ind. http://www.pbase.com/stephaubry/natrix_maura_220412
And I repost a pic of a subadult N. maura I saw in La Crau, France on Friday (http://fieldherping.eu/Forum/viewtopic.php?f=9&t=1094) because it shows a rare or atypical 3 postocular scales (more typical of N. tessellata instead the typical 2 of N. maura) and 2 preocular instead of 1.
more pics on http://www.pbase.com/stephaubry/natrix_maura_200412