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Introduction
Taxonomic Description and a hobbyist’s view of taxonomy. Notes on captive husbandry and further incidental ramblings about the Laddersnake.
The European Ladder Snake is one of the most hardy species out of all its European cousins, tolerant of temperature changes although enjoying warmer temperatures and is somewhat timid. Its often a spirited captive, enjoying its privacy in preference to interaction with the keeper.
Ladder snakes have a fairly chunky appearance with smooth scales. Ventral scales vary from a cream to yellow green in adults and a white with irregularly dotted black markings in the young. Hatchlings and juveniles additionally have crossbars against a silvery background, that joins the two longer lines and form a ladder like appearance, hence the common name for this species. This pattern usually fades along with the silvery appearance only after twelve to eighteen months or so, leaving the adults with brown or black stripes, from the neck to their tail, on an olive green background.
 
Taxonomic description Kingdom – Animalia
Phylum – Chordata
Subphlum – Vertebrata
Class – Reptilia
Order – Squamata
Suborder – Serpentes
Infraorder – Alethinophidia
Family – Colubridae
Subfamilies - Colubrinae
Genus – Rhinechis
Species – Rhinechis scalaris

A hobbyist’s view - brief digression

Formerly this species was lumped into the recently revised Elaphe group, now it is classified as Rhinechis scalaris since Helfenberger’s 2001 paper. No doubt further studies are to be carried out on the group formerly known as Elaphe, so heaven knows what further light will be shed about its relationship with other European rat snakes, although I feel the position of this species is currently pretty universally agreed upon. The overhaul of the Elaphe clan was long overdue and the Ladder snake is better off being separated from other members of that previous catch-all genus.

The Ladders placing in the genus Elaphe has long been uncomfortable; G. A. Boulenger (The Snakes of Europe - 1913) even felt they had a closer affinity to Coluber than any of the now former Elaphe clan and many keepers have commented on their similarities with Bull, Pine and Gopher snakes (Pituophis species), primarily due to their ‘robust’ nature and head shape. This shared superficial characteristic is due to sharing similar habits not any true relationship. To be fair, many if not most Elaphe species were originally classified as being Coluber from the early 1800’s.

The first time the Ladder snake was named as belonging to its own genus – Rhinechis, was in 1833 before being lumped into the artificial Elaphe genus in 1940. At that time it was given the species name of Rhinechis agassizilii by Michahelles. Its since been called a variety of other names including one I quite like, Coluber bilineatus, although the genus I’m not happy with, the species name seems apt to me. The snake after all does have two longitudinal lines, which serve as an instant identifier for adult specimens. The first time it has been described as Rhinechis scalaris was by Bonaparte in 1840, so Helfenberger has resurrected this monotypic genus to more accurately portray the animals’ divergent ancestry from other ‘Elaphe ’, this being the most valid previous description.

Of course, it’s easy to forget that all these previous classifications were based on what was known at the time. As such, it would be a little harsh to call them incorrect. For their time they were as accurate as could be or as accurate as the authors felt their descriptions were. Just like our latter day classification, it is as accurate as can be expected, bearing in mind, papers are in preparation seemingly all the time due to the advances in the modern ‘evidence’ gathering techniques of our day. An additional point is that of how slowly some ideas are likely to be taken up, when other seemingly contradictory evidence is reported. We have now reached or nearly reached the stage, where advances in taxonomy are slowed down by their very necessary peer review process prior to acceptance of some of the newer thoughts on how and what the implications of some of the animal relationship studies demonstrate.

A further note on taxonomy, in my opinion, any proposed reclassifications by Burbrink, Utiger, Schulz, Lenk & Wuster, Helfenberger (and perhaps soon to be Fry by venom/saliva analysis) etc., all have their place. I feel that they all present various ‘evidence’ that will sooner or later contribute to our accepted further understanding of the relationships of ‘rat snakes’ to each other and their ancestors. To use a poor analogy, I see all these studies as eye witness accounts. They may vary on some points and agree (sometimes uncomfortably) on others, none of which should be dismissed out of hand. All must be understood from their relative perspectives. The ‘truth’ is not an absolute. There is no such thing as black & white. As we learn more, we realise what little we know but we can also congratulate ‘our’ or more correctly, the relevant scientists for our increased knowledge, knowing we are indeed learning and advancing the search for the place that such and such animal occupies in the evolutionary tree. The fact that scientific (taxonomic) names are more inclined to change with increased frequency is just a reflection of our increasing techniques for better understanding of that animal and it’s placing with others of its kind. Adding to this the disagreement that exists, to what degree the divergence in characteristis of an animal constitute a species or subspecies, makes for interesting times too.

Some of the various tools available to the taxonomists are mtDNA & RNA analysis, morphological comparison (of body, eyes, scutellation, head shape, teeth, hemipenes, visceral organ topography – internal organ arrangement and proportion, osteology – the study of the skeleton and lastly in terms of importance - colouration and pattern, due to this being probably the most variable characteristic and the one most inclined to change over a shorter period of time due to local geographic niches occupied by an animal over it’s entire range). Also, it is very important to understand the significance of the historical environments that the animals came from. All animals’ bear some characteristics of what they once were or at least adaptations that are owed from the type of environment where they used to live or their habits. This has as much to do with ‘what’ an animal currently ‘is’, as to its present day predicament. As I said earlier, there is so much still yet to learn about so many species, the same can be said for my understanding of taxonomy too! I have said enough on my thoughts about taxonomy, apologies if I have made your eyes feel heavy, now back to the plot.

Native range and habitat

The native range of this species covers generally Spain and Portugal, the extreme south of coastal France including the Iles d’Hyeres, extending just over the Italian border holding a smaller range near the coastal area of Trucco and the eastern Island of Minorca in the Balearics.

Ladder snakes frequent a variety of Mediterranean environments, including sparse woods, hedges, scrubland, fields and farmland particularly where dry stone walls are prevalent. They may also be found around human habitation especially in farmland, attracted by the often accompanying rodents. They are terrestrial snakes that are quite able to climb trees and stony habitat, having few natural barriers. These snakes seek shelter in rodent burrows, Bee Eater burrows (where they share ranges), rock piles and hollow trees, choosing similar sites for hibernation. Groups of these snakes may sometimes be found sharing the same hibernacula during the winter possibly due to a shortage of suitable sites.

They are primarily diurnal but tend towards crepuscular and even nocturnal behaviour in warmer months. Having said this, it has been reported that they can display an ability to tolerate high temperatures, sometimes being active at the hottest part of the day even in midsummer. They appear to be able to tolerate marked temperature fluctuations. In studies of active specimens (Guillaume 1976), an average body temperature of 29C (84.2F) was recorded within a range of 21-36C (69.8-96.8F), so this would appear to be their ‘ideal’ or preferred body temperature. For most colubrid snakes that live in temperate climates, the preferred body temperature would usually measure around 26-28C (78.8-82.4F). Individuals have been found active at very low temperatures too, around 15C (59F) (Cheylan & Guillaume 1993). I’ve noticed that during brumation if my snakes reach a temperature of 15C (59F), they become almost as active as they are when kept in their normal temperature range, maybe indicating that their ideal brumation range falls in the 8-12C (46.4-53.6F) bracket – they certainly slow their movements down at this temperature becoming sluggish in movement and the rapidity of their tongue flicks decreasing.

In the warmest part of its range, Southern Portugal, hibernation probably isn’t necessary to any marked extent and they remain active throughout most of the year, presumably relying on other seasonal cues, like day length, increased temperatures and or rainfall to produce the required stimulus for mating.

Size and description
 
  Adult Ladder with retained juvenile pattern Hatchlings generally measure between 25-35cm and adults range from 120-160cm. There is one record of R. scalaris reaching 200cm (Schweizer 1924), which is mentioned in Schulz’s Monograph. Now that would be an impressive animal indeed. Adult males are usually bigger than adult females of the same age in my experience of previously keeping seven adults anyway. Other keepers of scalaris confirm these observations. Pleguezuelos et al, disagrees with this however, in his “Caracteres externes et coloration chez Elaphe scalaris de la peninsula Iberique” he observes that there is a distinct sexual dimorphism biased in favour of larger females. Schulz also notes this sexual dimorphism in favour of females’ greater length and bulk. I’m inclined to believe Juan Pleguezuelos et al, realising they have studied more animals throughout more of their range compared to the few myself and others that I know of have kept in captivity.

They possess a round black or brown pupil typical of many other diurnal species. Adults and their young have a pointed snout that is prominent to the profile of the lower jaw. Most often they have a black streak that runs obliquely on the side of their head. Adults have two dark brown stripes that run down the length of the body from the neck to tail. The background colour can be a uniform yellow, grey, pale brown, green brown, olive or more rarely a brick red colour. Melanistic animals are also known.

Ladder snakes have a fairly chunky appearance with smooth scales. Ventral scales vary from a cream to yellow green in adults and a white with irregularly dotted black markings in the young. Hatchlings and juveniles additionally have crossbars against a silvery background, that joins the two longer lines and form a ladder like appearance, hence the common name for this species. This pattern usually fades along with the silvery appearance only after twelve to eighteen months or so, leaving the adults with brown or black stripes, from the neck to their tail, on an olive green background.

Occasionally, some individuals retain a transitional juvenile pattern into adulthood as noted by Roger Butler in one of his adult females. I had an adult female of many years (now estimated at 14yrs) that partially retained a juvenile pattern, slightly less pronounced than a hatchling Ladder but quite striking on a silver grey background nonetheless (picture above). In addition to these two observations, I stumbled upon another reference of this juvenile pattern in two other adults via the internet on a German site. Apparently these are female specimens also, do I see a pattern emerging here (pun intended) with these female only reports?

My smallest male had the habit of turning lighter in the spring, the largest male I have doesn't. They all seem to be able to go slightly darker from time to time (independent of shedding), usually throughout winter. I don't recall any other keepers of R. scalaris commenting on this. Whether that means they haven't noticed, theirs don't change or my eyes are playing up, I don't know!

There are accounts of some Ladder snakes attaining at least nineteen years in captivity. I’d imagine that this life span is generally unlikely to be matched in nature, due to the normal pressures of ageing specimens being less efficient and robust than their younger counterparts at facing the various challenges of the wild, coupled with the likelihood of predation over the increasing years of the snakes’ life.
These snakes have 27 rows of dorsal scales across the body. Ventral scales number from 198-228. Sub-caudal scales range from 48-68. Usually 7-8 upper labials and occasionally 9, with the 4th and 5th or the 5th and 6th (if the upper labials number 9) having contact with the eye.
 
Behaviour
 
In the wild on occasion, they have been observed as being very aggressive and even savage, standing their ground rather than attempting to flee, although you would imagine that normally flight would be their first choice. Some can be fairly nervous and readily translate this into aggression. Demonstrations of this hostility are hissing and repeatedly striking at you. No serious injury results from this assault, as they don’t possess dangerously long teeth or thankfully any venom. Most of the ones I’ve kept could be described as being very aggressive but became calm if handled for a few minutes. Due to their highly strung nature, they benefit from being placed in a relatively low traffic area and sufficient cage furniture to provide a few hides.

Prey/food in captivity

Their unique rostral adaptation is a distinctive feature of the head and is used to burrow, further excavate burrows, upturn stones, logs, detritus and other obstacles in the pursuit of their prey; nestling rodents, rabbits, lizards, amphibians, chick and adult birds. Merops apiaster commonly called European Bee eaters, are slender attractive brightly coloured migratory birds that winter in Tropical Africa, they can often nest in long tunnels over a metre in length. They can lay up to 8 eggs during the late spring/early summer, where the two animals exist, their eggs and young can provide a seasonal source of food during spring along with other chicks and birds.

Ladder snakes tend to pin their prey rather than constrict, although if quarry is large enough to accommodate their coiled body they will constrict prey as well. So long as their prey is secured they often don’t attempt to kill prey before swallowing. R. scalaris climb walls and trees searching for prey, usually avian but this trait is possibly also of benefit in flushing out other potential prey. They have been observed to eat bird and lizard eggs in the wild as well as their own in captivity too.

Ladder snakes don’t have it all their own way. A fairly large variety of birds will prey on juvenile and adult ladders alike. Adult individuals will attempt to coil around the legs of Short Toed Eagles - Circaetus gallicus, or any other large raptor, in an effort to foil their attempt to bite the snakes head. These birds of prey dine mainly on snakes also taking venomous species dispatching them in the same manner, by pinning the snake down and attacking the head causing fatal injury to the snake prior to consuming it.

In the wild the European Ladder snake would eat a varied diet of prey that in turn has eaten an equally diverse diet. In a brief reference to a study of wild R. scalaris in Alicante on the internet, (second internet reference given at the conclusion of this text), it claims that their diets were made up of more arthropods than birds! I find this hard to believe as a normal trait for this species, unless the individuals studied were very young snakes or there was an abundant source of insect eating prey like lizards or of course birds and the bugs were passed from the stomach of their prey to theirs, neither of which scenarios were clear in the passing reference provided.

Ladder neonates are reported as eating grasshoppers, other bugs and nestling rodents in the wild, like many other juvenile snakes. You would imagine that the rate of their linear growth must be greatly diminished, when compared to other juveniles of similar proportions, eating a more nutritious prey that is based primarily on rodents.
The basis of their food intake more usually, is unsurprisingly for a rat snake, small rodents along with small rabbits and birds. Small lizards, frogs and anything else of a suitable size that they can over power, would also likely be consumed, possibly even including snakes too. Obviously the animals preyed upon, would have eaten a pretty broad range of items in turn and therefore a varied mixture of food stuffs will have been consumed containing a balance of minerals and vitamins.
 
Likewise, offering your irascible friends a wide variety of food in captivity where available and where possible can only be complimentary to their overall health. Possible dishes on their menu could include mice, chicken and quail chicks, rats, very small or baby rabbits, gerbils and hamsters, of a suitable size. My charges seemed to relish baby rabbits in particular, when I can get them.
Hatchlings should be fed pinkies every five to seven days they don’t typically present a problem taking readily available pinkies. Adult snakes will take medium to large mice or small rats, depending on the proportion of the snake, every seven to ten days. I try and avoid a strict routine of feeding on the exact same day every week. This isn’t borne out of any special requirement, just a desire for diversity. On occasion, I’ve observed them strike at the mice offered on forceps and retreat with the mouse into cover, only for me to find the mouse uneaten and hidden in the substrate a few days later. The smell of decomposing rodent isn’t the most pleasant of smells but at least it alerts you to its presence. Fortunately, this doesn’t happen often, as they usually have a very healthy appetite.
Unless we are talking about a gravid female and you can see the skin between their scales, it is likely that you are feeding them too much. Reduce the size or frequency of their meals to rectify this. Fresh water should be provided at all times, placed away from the heat source to ensure against adverse humidity in the vivarium. I also place food away from the heat source so that it doesn’t go off too quickly, not that this is usually a problem as they generally have excellent appetites, eating as soon as they feel safe. They might not appreciate noses pressed to the glass of the vivarium when ‘grubs up’ though!

Housing

An enclosure measuring 90cm X 60cm X 60cm  (as a minimum) with sufficient furniture should be adequate for a Ladder snake of less than 120cm. If more room can be spared then that would probably be better, certainly if the tenant is any larger than this, then so should be the vivarium.
Ladders tend to be quite active from time to time, so a consideration should include any internal fixtures are made secure to avoid possible harm to the snake. If you prefer an upright arrangement for the vivarium be sure to furnish with lots of branches and a few shelves at different levels, so that the snake can climb to attain the temperature it requires. If a drawer is provided with a branch or two along with a shelf, then the actual surface area the snake can move about on will be greatly increased. When not using a drawer system, where the animal can hide away from the hustle and bustle of external activity, a suitable amount of hides should be provided depending on the layout of the enclosure. They will benefit from as much cover as can be provided. Hatchlings can be housed in a small plastic secure box with a substrate of newspaper or paper kitchen towel, a small water bowl and a cardboard toilet roll insert as a hide, flattening a side to prevent this from rolling around is a good idea.
  The substrate for adults can be wood chip or shavings, bark chip, shredded paper, two to three week old newspaper – to allow the ink to dry or similar. Any kind of paper is useful if you want to keep an eye on health problems and to make sure that mice aren’t being hidden in dense substrate rather than being eaten. If the snake is healthy then bark chips or something they can burrow in, dry peat/sphagnum moss mix would probably provide them with a substrate they can feel more secure in. It would likely offer more traction while exploring their environments too. Care should be taken to remove and tidy up any spillages from the water bowl and clean regularly, to ensure moisture doesn’t build up within their enclosure and everything is kept dry.

As always, a thermal gradient should be arrived at, ranging from 20-32 Celsius, with possibly a hot spot of up to 35 Celsius if space within the Vivarium allows for this. This temperature can be allowed to fall overall by around 5-10 degrees at night. These levels can be achieved with either heat mats/tape, ceramic heaters or protected incandescent light bulbs, depending on the external temperature of the room and the size of the vivarium to be heated. The resultant temperature inside the vivarium may require any combination of heat sources to provide these conditions. Thermostats and thermometers, should as ever, be used to make sure temperatures don’t fall or rise too much outside of this range. In the past I’ve used a combination of heat mats with a flat rock covering and ceramics for a heat source but I may well incorporate a bulb to simulate day/night cycles sometime in the future. When I first wrote this account, the only light they received was via the window (and this was never direct to avoid reaching excessive temperatures on warmer days). I’ve had no problems with natural daylight; I suppose it’s only down to curiosity that I wish to try artificial lighting, when I next get the opportunity of keeping this species.

Humidity should be normal at around 40 – 60%. If problems occur with shedding, then placing a damp pillow case or moist sphagnum moss in their favourite hide for the duration of the shed will help them complete the slough. When this has been accomplished the humid source should be removed. Once I had to do this with a single female, touch wood, I didn’t experience a repeat and it was a mystery as to why she struggled to achieve a clean slough then.
 
This site has information on the following genera of Ratsnakes ... Spilotes, Spalerosophis, Ptyas, Zamenis, Elaphe, Rhinechis, Senticolis, Pseudelaphe, Pantherophis, Bogertophis, Orthriophis, Gonyosoma, Oreocryptophis, Oocatochus, Euprepiophis, Coelognathus, Archelaphe