black grassie

Just had a phone call today passing on a message about another melanistic grass snake in Derbyshire last year, it was a 3 year old male found last September basking on the tarmac of a closed off road. The ecologist who passed it on has frequently seen normal coloured grassies in nearby fishing ponds and elsewhere in this area. Its probably the third  melanistic from last year in the area between Chesterfield and Alfreton, with a definite record of a juvenile seen in June at North Wingfield and a report two days earlier of an adult black snake in a nearby fishing pond, almost certainly being another grassie (No adders in that area).
There definitively seems to be a genetic trait in this area throwing up occasional dark or melanistic ones in a largish population of normal coloured ones. They have now been found over a distance of 10kms, and the September one is not only the furthest south but has extended the area into a different river catchment. All the others are around the headwaters of the River Rother which flows north to the join the Don at Rotherham, whilst that one is in the headwaters of streams running down to the River Derwent, a tributary of the Trent.