About Natrix astreptophora Seoane, 1885
The red-eyed grass snake, scientifically named Natrix astreptophora Seoane, 1885, can be distinguished from all other grass snakes by its reddish irises and fewer ventral scales. This species is known to exhibit erythrism. There are three disjunct populations of the red-eyed grass snake. The European population is found in the Iberian Peninsula and Occitania, located in southwestern France. The population in the Maghreb is split into two separate disjunct subpopulations: one in northern Morocco, and one in northwestern Tunisia and northeastern Algeria. The red-eyed grass snake typically preys on fish and amphibians, and also consumes small mammals and juvenile birds. Like some other grass snakes, red-eyed grass snakes are known to raise their forebody and flatten their necks to imitate cobra behaviour, even though the ranges of red-eyed grass snakes and cobras do not overlap today. This behaviour is a relict trait from the Pliocene to Pleistocene era, when cobras were present in Europe and lived in the same areas as these grass snakes. Red-eyed grass snakes reach sexual maturity at 5 years of age. Egg-laying occurs in July and August. It is thought that young females lay clutches of around ten eggs, similar to the closely related barred grass snake, while older females can lay as many as 100 eggs. Red-eyed grass snakes have been recorded infrequently interbreeding with other Natrix grass snakes. They interbreed very rarely with the barred grass snake where the ranges of the two species meet, and gene flow between these two species is almost negligible. Hybridization between the red-eyed grass snake and the more distantly related viperine water snake has also been recorded in Andalusia, southern Spain.
