Reproductive Traits and Hatchling Characteristics of the Endemic Sardinian Grass Snake (Natrix helvetica cetti): First Field Data, with Screening for Ophidiomyces ophidiicola

The Sardinian grass snake, Natrix helvetica cetti, is an island-endemic subspecies with a restricted and highly fragmented distribution confined to Sardinia, Italy. Information on its reproductive biology and wild offspring remain scarce in the scientific literature. This present study reports the first recorded data on a clutch of eggs laid by a wild melanistic female N. h. cetti that exhibited lethargy when observed basking, prompting a brief period of health monitoring and screening for the presence of the pathogenic fungus Ophidiomyces ophidiicola (Oo). The clutch yielded nine hatchlings, for which phenotypic data are provided and compared with existing information on the Natrix natrix complex. Both the adult female and its offspring tested negative in the Oo screening. The body size of the adult grass snake, specifically its snout-to-vent length of 48.3 cm, is the smallest ever recorded for a gravid female N. helvetica. This may indicate that maturity is reached at particularly small sizes, a distinctive trait of this intriguing island subspecies, suggesting the need for further investigation.