Distribution and characterization of melanism in Grass Snakes from Italy.

In snakes, melanism can improve thermoregulation efficiency, reproductive success and provide additional protection to internal organs from solar radiation. For these reasons, such conditions could be beneficial for animals living in both cold and warm environments. For widely distributed species of grass snake (genus Natrix), several single encounters of melanic individuals are reported in the literature. In the period 2015-2021 a significant number of unpublished observations of melanic Natrix helvetica and N. natrix were collected on the Italian territory and integrated with bibliographic data. The present work illustrates the chromatic variation within melanic individuals and investigates their distribution. Within the chromatic variability of melanic individuals, two main forms of melanism were detected in N. helvetica. They show an almost parapatric distribution throughout the national territory which raises interesting questions about their potential adaptive advantages in different ecological and climatic contexts.