grass snake

Like its congeners, the body is brown to olive, sometimes gray. It is difficult to differentiate from N. helvetica with which it shares many morphological characteristics.

As its name indicates, it has a collar-like pattern around the neck. This is manifested by whitish to golden spots with a black band upstream that enhances the colors. It is more pronounced in young individuals and gradually fades with age. Contrary to N. helvetica, the collar spots are always a uniform color. They are two-colored in its close cousin.

The scales are keeled, with a prominent ridge in the center. Those on the head are wider, sometimes rectangular. There are seven upper labial scales.

Apart from its congeners, young N. natrix are sometimes confused with Aesculapian snakes (Zamenis longissimus) and green and yellow snakes (Hierophis viridiflavus). The neck pattern is similar, however, these two do not have keeled dorsal scales.

The grass snake is one of the most aquatic snakes in Europe. It usually frequents stagnant or slow-flowing waters in which it hunts its preferred prey: amphibians. An excellent swimmer, it sometimes shares its environment with other freshwater snakes, such as N. Tessellata. Intimacy between various populations does not generate aggressive behavior. Although it accepts its cousins, the snake is a solitary animal outside of reproduction.

Outside the water, it sunbathes on the riverbanks or in habitats at the forest edge. Due to its secretive nature and brief escapes, some of its biology is still under study. Long sunbathing sessions allow snakes to warm up and aid digestion.

Males and females feed on the same prey, but in different proportions. Females are more likely to target large toads and sometimes small mammals. Males focus on frogs and tadpoles. In mountainous areas, the grass snake also hunts newts and salamanders. During aquatic hunting sessions, this species uses its remarkable olfactory senses. It is also capable of detecting the waves emitted on the water's surface by amphibians as they croak.

Males are relatively sedentary. They mainly move during the breeding season, between May and June. Females move before and after egg-laying, which is explained by the search for a suitable birthing site. They bask in the sun to warm up or digest. At the slightest alert, they dive or seek refuge in vegetation.

Like its congeners, the grass snake can deploy an arsenal of tricks and deceptions to escape predators. If it cannot flee, it may attempt intimidation displays by mimicking other snakes. It can imitate vipers and cobras by flattening its head. This strategy particularly scares wary migratory birds of venomous snakes. In addition to this behavioral mimicry, it can hiss loudly or coil around the aggressor, secreting a repugnant whitish liquid from its cloacal glands.

The last, and not the least, defense is its ability to play dead. It flips onto its back, opens its mouth, tongue hanging out, and releases blood from its nose and mouth. It also regurgitates its foul-smelling liquid to indicate to the predator that it is inedible. At the slightest distraction from the predator, it quickly disappears into the vegetation or plunges into nearby waters.

As soon as the cold season begins, the grass snake seeks a shelter to hibernate. During this period of inactivity, it resides in holes, leaf piles, tree stumps, or even haystacks. It can also enter basements or cellars.

As in other Natrix species, males and females mate in groups. The larger males have a better chance of fertilizing females during these long mating activities.

A few weeks after mating, the female lays around thirty eggs in a warm and humid shelter. For example, she may use rodent burrows or dried-up stream beds. At birth, the young are independent and must learn to hunt on their own. Measuring about twenty centimeters, they are preyed upon by many wading birds and mammals during the first few weeks.