Variation in the occipital color pattern of grass snakes based on iNaturalist records. Small inset map (top) shows subspecies distribution according to Asztalos et al. (2021a): Natrix natrix natrix – yellow, N. n. vulgaris – red, N. n. moreotica – grey, N. n. scutata – green. Hybrid zones hatched. Note that the occurrence of closed collars is largely restricted to the range of N. n. scutata and to the hybrid zones between N. natrix and N. helvetica in the very west. Grass snakes with lacking occipital pattern occur in the southwest, within the distribution range of N. n. moreotica, and again in the hybrid zones of N. natrix and N. helvetica. It is well known that the collar may fade and disappear in aged N. helvetica (cf. Kabisch 1999; Meyer 2020). According to the photo material, the same is true for N. n. moreotica.