The ladder snake (Zamenis scalaris ) is a species of non-venomous snake in the family Colubridae. The species is endemic to southwestern Europe.
The Ladder snake is a non-venomous snake native to southwestern Europe. As an adult this snake is less variable than many related snake species, the basic color goes from yellowish to dark brown, with two darker stripes running down the length of the body from neck to tail. It normally also has a dark stripe running from the rear of the eye to the angle of the jaw and sometimes subtle, darker markings on the sides. The ventral side is pale, varying from a silvery-grey to whitish, with the occasional dark spot. The juvenile snakes have lighter and brighter coloration, varying from yellow to light brown, with the characteristic “ladder” pattern picked out in black along the upper side. The pale underside has black markings which sometimes coalesce to cover the whole of the underside. As the snake ages, these colors and patterns fade until the simpler adult pattern is left.
Ladder snakes occur in Portugal, Spain, southern France, and just into Italy, also Menorca and the Iles d'Hyères off Provence. They favor scrub bushy cover, including orchards, vineyards, hedges, and overgrown dry-stone walls; they are common in the maquis (shrubland biome). Habitats with stones and boulders and low shade are usually preferred the most.
Ladder snakes are solitary and normally active by day. During the hottest summer months, however, they may be nocturnal, while in the spring months they may be more crepuscular. They are aggressive and defensive in their nature. Defensive signals include hissing and lunging forward with the mouth open. Any attempt to pick up this snake may be greeted by sharp bites and also the emptying of the cloacal glands, releasing an offensive odor. Ladder snakes are mobile creatures and may move up to 100 m per day, while the average home territory of an individual is 4,500 sq. m. Adults may enter barns or similar buildings in search of rodent prey, but they do not normally use such places for shelter and prefer rodent burrows, piles of stones, or hollow trees.
Ladder snakes are carnivores. They mainly feed on mammals such as mice, rabbits, and shrews and will also eat spiders, insects (especially grasshoppers), and a few birds. To prey on birds Ladder snakes will climb to search for active nests in trees or on man-made structures. Lizards are also eaten. Juveniles prefer small lizards, baby rodents, spiders, and grasshoppers.
The breeding season of Ladder snakes varies depending on location. In Iberia courtship occurs during May and June, however, some females do not breed every year. About 3-6 weeks after mating the female lays a clutch between 4 and 24 eggs. Incubation takes from 5 to 12 weeks. The young measure 20 cm long as hatchlings. Unusually for snakes, their mother may remain with the newly hatched juveniles for a few days. Males and females become reproductively mature at approximately 5 years of age, when they reach a length of 50 and 65 cm, respectively.
The Ladder snake is a generally abundant species and it is not considered threatened at present. However, locally it suffers from a lack of vegetation which it uses for cover with is caused mainly by agricultural activities and often becomes a victim of road mortality.
According to IUCN, the Ladder snake is widespread throughout its range but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.
