Aesculapian snake

Appearance

The snakes hatch at around 30 cm . Adults are usually from 110 cm to 160 cm in total length, but can grow to 200 cm. They are dark, long, slender, and typically bronzy in color, with smooth scales that give them a metallic sheen.

Juveniles can easily be confused with juvenile grass snakes, also having a yellow collar on their neck that may persist for some time in younger adults. They are light green or brownish-green with various darker patterns along the flanks and on their back. Two darker patches appear in the form of lines running on the top of the flanks. The head in juveniles also features several distinctive dark spots, one hoof-like on the back of the head in-between the yellow neck stripes, and two paired ones, with one horizontal stripe running from the eye and connecting to the neck marks, and one short vertical stripe connecting the eye with the 4th to 5th upper labial scales.

Adults are much more uniform, sometimes being olive-yellow, brownish-green, sometimes almost black. Often in adults, there may be a more or less regular pattern of white-edged dorsal scales appearing as white freckles all over the body up to moiré-like structures in places, enhancing the shiny metallic appearance. Sometimes, especially when pale in color, two darker longitudinal lines along the flanks can be visible. The belly is plain yellow to off-white, while the round iris has amber to ochre coloration. Melanistic, erythristic, and albinotic natural forms are known, as is a dark grey form.

Although there is no noticeable sexual dimorphism in coloration, males grow significantly longer than females, presumably because of the more significant energy input of the latter into the reproductive cycle. Maximum weight for German populations has been 890 grams for males and 550 grams for females . Other distinctions, as in many snakes, include in males a relatively longer tail to total body length and a wider tail base.

Scale arrangement includes 23 dorsal scale rows at midbody, 211-250 ventral scales, a divided anal scale, and 60-91 paired subcaudal scales . Ventral scales are sharply angled where the underside meets the side of the body, which enhances the species' climbing ability.

Lifespan is estimated at about 25 to 30 years.

Distribution

There are two populations of Aesculapian snake which derive from escapes in Great Britain. The older one is in the vicinity of the Welsh Mountain Zoo near Conwy in North Wales This population has persisted and reproduced for at least the last 30 years....hieroglyph snipped... A second, more recent population has been found in and around Regent's Park near Regent's Canal in London...hieroglyph snipped... and said to number up to 30. It is suspected this colony may have been there some years, undetected.

Status

Though the Aesculapian Snake occupies a relatively broad range and is not endangered as a species, it is thought to be in general decline largely due to anthropic disturbances. The snake is especially vulnerable in fringe parts and northern areas of its distribution where given the historic retreat as a result of climatic changes since the Holocene climatic optimum, local populations remain isolated both from each other and from the main distribution centers, with no exchange of genetic material and no reinforcement through migration as a result. In such areas active local protection is due and the snake for example has been locally classified as Critically Endangered in the German Red List of endangered species. In most other countries including France, Switzerland, Austria, the Czech Republic, Slovakia, Hungary, Bulgaria, Poland, Ukraine and Russia it is also under protection status.

Among the key concerns is human-caused habitat destruction, with a series of respective recommendations concerning forestry and agriculture as to the protection through non-intervention of the species' core distribution centers including targeted protection of potential hatching and hibernation places such as old growth zones and fringe ecotones near such woodland areas.

A significant threat also are roads both in terms of new construction and rising traffic, with a risk of further fragmentation of populations and loss of genetic exchange.

Behavior

The snakes are active by day. In the warmer months of the year, they come out in late afternoon or early morning. They are very good climbers capable of ascending even vertical, branchless tree trunks. The snakes have been observed at heights of 4–5 m and even 15–20 m in trees, and foraging in the roofs of buildings. Observed optimum temperature for activity in German populations is 20-22 °C and they are rarely recorded below 16 °C or above 25 °C, other observations for Ukrainian populations put minimum activity temperature from 19 °C and optimum to 21-26 °C. Above around 27 °C they try to avoid exposure to direct sunlight and cease activity with more extreme heat. The snakes will exhibit a degree of activity even during hibernation, moving around to keep a body temperature near 5 °C and occasionally emerging to bask on sunny days. The average home range for French populations has been calculated at 1.14ha, however males will travel longer distances of up to 2 km to find females during the mating season and females to find suitable hatching sites to lay eggs. The Aesculapian Snakes are deemed secretive and not always easy to find even in areas of positive presence, or found in surprising contexts.

In contact with humans, they can be rather tame, possibly due to their cryptic coloration keeping them hidden within their natural environment. They usually disappear and hide, but if cornered they may sometimes stand their ground and try to intimidate their opponent, sometimes with a chewing-like movement of the mouth and occasionally biting.

It has been speculated that the species may be actually more prevalent than thought due to spending a significant part of its time in tree canopy, however no reliable data exist as to what part that would be. In France it is said to be the only snake species that occurs inside dense, shadowy forests with minimum undergrowth, presumably because of using foliage for basking and foraging. In other parts of the range it has been reported to only use the canopy on a more substantial basis in largely uninhabited areas, such as the natural beech forests of the East Slovak and Ukrainian Carpathians, with similar characteristics.

Habitat

The Aesculapian Snake prefers forested, warm but not hot, moderately humid but not wet, hilly or rocky habitats with proper insolation and varied, not sparse vegetation that provides sufficient variation in local microclimates, helping the reptile with thermoregulation. In most of their range they are typically found in relatively intact or fairly cultivated warmer temperate broadleaf forests including the more humid variety such as along river valleys and riverbeds and forest steppes. Frequented locations include places such as forest clearings in succession, shrublands at the edges of forests and forest/field ecotones, woods interspersed with meadows etc. However, they generally do not avoid human presence, being often found in places such as gardens and sheds, and even prefer habitats such as old walls and stonewalls, derelict buildings and ruins that offer a variety of hiding and basking places. The synanthropic aspect appears to be more pronounced in northernmost parts of the range where they are dependent on human structures for food, warmth and hatching grounds. They avoid open plains and agricultural deserts.

In the south their range seems to coincide with the borderline between deciduous broadleaf forests and mediterranean shrublands, with the latter presumably too dry for the species. In the north their line of presence appears temperature-limited.

Reproduction

Minimum length of individuals entering the reproductive cycle has been reported at 85–100 cm, which corresponds to sexual maturity age of about 4–6 years. Breeding occurs annually after hibernation in spring, typically from mid-May to mid-June. In this time the snakes actively seek each other and mating begins. Rival males engage in ritual fights the aim of which is to pin down the opponent's head with one's own or coils of one's body; biting may occur but is not typical. The actual courtship takes the form of an elegant dance between the male and female, with anterior portions of the bodies raised in an S-shape and the tails entwined. The male may also grasp the female's head with its jaw . 4 to 6 weeks after about 10 eggs are laid in a moist, warm spot where organic decomposition occurs, usually under hay piles, in rotting wood piles, heaps of manure or leaf mold, old tree stumps and similar places. Particularly in the northern parts of the range, preferred hatching grounds often are used by multiple females and are also shared with Grass Snakes. The eggs incubate for around 8 weeks before hatching.

Food

Their main food source are rodents up to the size of rats and other small mammals such as shrews and moles. They also eat birds as well as bird eggs and nestlings. They suffocate their prey by constriction, though harmless smaller mouthfuls may be eaten alive without constriction, or simply crushed on eating by jaws. Juveniles mainly eat lizards and arthropods, later small rodents. Other snakes and lizards are taken, but only found rarely in adult prey.

Predators include badgers and other mustelids, foxes, wild boar , hedgehogs, and various birds of prey . Juveniles may be eaten by smooth snakes and other reptilivorous snakes. Also a threat mainly to juveniles and hatches are domestic animals such as cats, dogs, and chickens, and even rats may be dangerous to inactive adult specimens in hibernation. In areas of concurrent distribution, they are also preyed upon by introduced North American raccoons and east Asian raccoon dogs.

Predators

Their main food source are rodents up to the size of rats and other small mammals such as shrews and moles. They also eat birds as well as bird eggs and nestlings. They suffocate their prey by constriction, though harmless smaller mouthfuls may be eaten alive without constriction, or simply crushed on eating by jaws. Juveniles mainly eat lizards and arthropods, later small rodents. Other snakes and lizards are taken, but only found rarely in adult prey.

Predators include badgers and other mustelids, foxes, wild boar , hedgehogs, and various birds of prey . Juveniles may be eaten by smooth snakes and other reptilivorous snakes. Also a threat mainly to juveniles and hatches are domestic animals such as cats, dogs, and chickens, and even rats may be dangerous to inactive adult specimens in hibernation. In areas of concurrent distribution, they are also preyed upon by introduced North American raccoons and east Asian raccoon dogs.

Evolution

The Aesculapian Snake was first described by Josephus Nicolaus Laurenti in 1768 as ''Natrix longissima'', later it was also known as ''Coluber longissimus'' and for the most part of its history as ''Elaphe longissima''. The current scientific name of the species based on revisions of the large genus ''Elaphe'' is ''Zamenis longissimus''. ''Zamenis'' is of unknown origin, however ''longissimus'' comes from Latin and means "longest"; the snake is one of the longest over its range. The common name of the species — "Aesculape" in French and its equivalents in other languages — refers to the classical god of healing whose temples the snake was encouraged around. It is surmised that the typical depiction of the god with his snake-entwined staff features the species. Later from these, modern symbols developed of the medical professions as used in a number of variations today. The species along with Four-lined Snakes also is carried in an annual religious procession in Cocullo in central Italy, which is of separate origin and was later made part of the catholic calendar.