Dione rat snake Elaphe dione Pallas, 1773: survey of geographical and selective variations of the collection of Tula Exotarium

Ivan Yu. Arinin

Herpetologist

Exotarium

Oktyabrskaya, 26,

300002, Tula, Russia

E-mail: ivan_arinin@pisem.net

Introduction

Dione rat snake Elaphe dione is known to the terrarium-keepers of practically all countries who in a more or less degree have a developed tradition of keeping of reptiles. In spite of this fact it is rather rarely encountered in the collections of terrarium-keepers because it is considered to be a species of little attractiveness – at first sight it has neither the challenge of rare and problematic in keeping animals nor a bright appearance characteristic to many snakes which at present are widely distributed in herpetoculture.

Nevertheless, in spite of such a prejudiced opinion, this species has all qualities which are necessary for a popular terrarium animal. Occupying an enormous distribution area extending from the South Ukraine to the Korean Peninsula, Dione rat snake has an incredible ecological flexibility allowing it to inhabit practically all habitats present in its distribution range and to perfectly adapt to captive conditions. On the other hand, this species also has a certain scientific interest. For example, in several regions the borders of its distribution area require to be defined more precisely, a number of questions of its taxonomy also remain unclear because populations of E.dione are separated by thousands kilometers and each of them has its own unique characters. And, at last, owing to such an extensive distribution and a great diversity of conditions of inhabiting the species is characterized by a highest variability in colouration and pattern which makes it attractive for selective work as well.

In this article we will try to consider a number of geographical and received by us in the process of selective work variations from the collection of Tula Exotarium because many of them have been and remain up to now little-known for a wide circle of terrarium-keepers.

Brief history of E.dione group

Work with the group of Dione rat snakes in Tula Exotarium was initiated in 1995 by Sergei Ryabov. During the period lasted till 2001 he made an enormous work on collecting of the information about the geographical distribution of E.dione and adding new specimens to the collection. Owing to extensive international contacts specimens practically from all regions of the distribution area of the species were collected. At that period the foundation of selective work which is carried out at present was also laid – a series of interesting and bright variations was received.

Since 2001 in the result of enlarging of the total collection of Exotarium and lack of specialists we were forced to reduce the group of Dione rat snakes. At the present moment, after several rather poor years, it is being restored, and a relatively successful breeding season allowed not only to partly replenish the collection, but to receive new interesting variations as well. Thus, at present it includes 56 specimens, and we are doing our best for its further development.

Geographical variations

Since at present the system of names for variations is not worked out to a sufficient degree, we accept most of them as working variants which can be changed in the future.

Normal

The most phenotypically stable geographical variation distributed mostly in South-East Ukraine, South Russia, Azerbaijan, Uzbekistan, Turkmenistan and Tadzhikistan (Alekperov, 1978; Shammakov, 1981; Bakiev, Faizulin, 2002; Vashetko, Chikin et al., 2003). The characteristic colouration consists of tones from grey to light-brown, in some regions very dark specimens can be encountered. The patterns consists of four indistinctly marked longitudinal stripes, two of which are situated on the snake’s dorsum and over which two rows of darker blotches of a rounded form run.

Since this is one of the most widely distributed in the wild and available to the world variations, Normal most often gets into collections of terrarium-keepers, and in many respects exactly owing to this variation the species has an image of an unattractive and not very interesting snake.

Nigrita (formely Melanistic)

Known for a rather long time, but introduced into herpetoculture only several years ago, interesting and unique in its own way colour variation Nigrita was received by us from the vicinity of Mozdok town (North Osetia, North Caucasus).

This variation is characterized by a uni-coloured black colouration with a lighter venter. Two thin white longitudinal striped which completely disappear in some specimens run along the back. There are also completely black specimens which in outer appearance resemble Persian rat snake (Z.persicus Werner, 1913) (Ryabov, 2001).

In spite of the fact that Nigrita is kept in our collection since the year 2000 we were able to achieve successes in its breeding only in 2004. The breeders were received from a clutch laid by a female which was fertilized in the wild. While wild-caught males, in spite of various methods of stimulation of breeding, were completely indifferent, a young male successfully copulated not only with its partner, but with a wild-caught female as well. In connection with the fact that captive-bred specimens do not have such a strict attachment to natural regimens we hope that in the future we will not have such problems with breeding of this variation. In the near future we plan to establish a rather large group breeding on a stable basis.

Tenebrosa

At present the borders of the distribution area of this variation are not known precisely and require a more detailed study. It is known for certain that its distribution range covers Eastern Kazakhstan and adjacent to it Altai region.

Tenebrosa is one of the most interesting natural variations of Dione rat snake. Typical for the species in general longitudinal stripes and blotches disappear completely in this variation changing to uni-coloured olive, brick-brown or dark-cherry colouration. Owing to such a peculiar appearance Sobolevsky in 1929 distinguished the variation as a separate subspecies, but later the sub-specific status was eliminated (Bannikov et al., 1977; Obst & Scherbak, 1993).

There is also a colour phase of Tenebrosa which has a well defined dorsal pattern differing from the scheme characteristic for the species in general by the fact that blotches either fuse together by pairs forming transverse bands, or when they are arranged non-symmetrically they form a peculiar checkered pattern, or they turn into an intricate pattern running along the spine of the snake. Since in this case the appearance is evidently in a contradiction with the name (tenebrosa in Greek - dark, uni-coloured) at present we accept a working name Tenebrosa Blotched Phase.

Also interesting is the fact that in the result of mating of a pure-blooded Tenebrosa and a specimen from the Chinese population uniform offspring with transverse bands (without blotches) was received (Ryabov, pers. comm.). A specimen of Tenebrosa is also known which had a non-typical pattern – one single light stripe with black edges running on the spine (Ryabov, pers. comm.).

Baikal Lake

The region of the Baikal Lake remains insufficiently investigated. As a rule, the information about the variations occurring there is limited by personal communications, in our collection we keep a single specimen wild-caught on the Olhon island.

Because of the lack of data it is difficult to form an opinion is the phenotype of the specimen we have is typical or it is a result of an individual variability. Our specimen has a rather peculiar appearance – its colouration consists of very light tinges of grey (practically getting as far as white) with slightly darker longitudinal dorsal stripes and contrasting black blotches surrounded by light aureoles. The main characteristic feature of this variation is a very dark underside, in some cases anthracitic-black (Ryabov, pers. comm.).

The working name of the variation is Baikal Lake but when forming a rather large group of specimens from this region the name can ba changed, the more so that E.dione from Mongolia have similar external characteristic features (Borkin et al., 1990; Obst & Scherbak, 1993).

It must be noted that young specimens from Shaanxi Province (vicinity of Xian town) which we received in 2004 from Rainer Fesser have clearly defined characters of this variation, in particular the aureoles around dorsal blotches. Possibly they are only elements of a juvenile colouration which disappear with age, that is why now it is difficult to make some conclusions.

Chersky-complex

Specimens originating mainly from the Russian Far East – Khabarovsk Territory, Amur Region and Primorsky Territory (Emeljanov, 1929; Kolobaev, Trilikauskas, 2003; p.d.) are characterized by a highest degree of variability in the colouration and pattern that is why they are preliminary united into one complex. The only characteristic feature by which we determine this variation is the presence of ventral blotches which have a regular rectangular form. The scheme of their arrangement has three variants – the blotches can run in two rows on the edges of the venter or they can be arranged in a checkered order, in the third case they are as though plunged into deeper layers of epidermis and thus an impression of a three-dimensional arrangement is created. But mainly we unite according to the geographical principle because all enumerated features are characteristic only for Far Eastern population.

The name “Chersky” originates from the family-name of the famous Russian scientist A.Chersky who in 1915 gave a specimen from the Far East to Nikolsky who described it as a separate species E.cherskii (later he synonymized it with E.dione). It became widely known owing to Sergei Ryabov who for the first time used it as a working name for the Far Eastern variation.

As a rule, grey and brown tines prevail in the colouration of Chersky, but specimens with elements of yellow, light-pink and red are encountered. Dorsal blotches, in contrast to other variations, are more elongated dorso-ventrally sometimes fusing together with their upper parts. Longitudinal stripes practically disappear, in some specimens it is possible to define them only by lighter borders. This diversity can be caused by a possible extension of the borders of the distribution range of the species in the region to the north, because specimens received from the southern part of the Far Eastern region have clearly marked features of Chinese or Korean population which gradually disappear towards the northern borders.

One of the most interesting for selective work is the variation Chersky Tiger presumably wild-caught in the north-eastern part of China (Ryabov, pers. comm.) with a dark-cherry colouration and dorso-ventrally elongated blotches. Exactly when using of the genetic potential of the Chersky complex by a selective work all bright forms currently kept at Exotarium were received.

China (Chinensis, Yellow)

The borders of the distribution area of this variation require to be defined more precisely. We have a group of specimens received from the left-bank region of the flood-plain of Yangtze river. Schulz (1996) also reports about occurrence in this province of the population which has similar external characteristic features. On the other hand it is known that in the north-western part of the distribution area (Sichuan Province) there are specimens which practically do not have differences in outer appearance from typical E.dione Normal (Zhao Ermi, pers. comm.), and the north-eastern part of China is evidently occupied by Chersky complex (Ryabov, pers. comm.).

Representatives of the south-eastern population are distinguished by a most bright colouration – tones of yellow prevail in it – from light, sandy to rich colours with tinges of pink. Dark-brown longitudinal stripes are very clearly marked, blotches with a slightly darker colouration and of a peculiar rhomboid shape visually are arranged very densely.

Terrarium-keepers know E.dione China rather well because, as they have a bright coloration, d they are exported from China more frequently. At the moment the names Chinensis and Yellow are used as working names.

Northern Korea (Dark Yellow)

Specimens received from North Korea are kept in the collection of Tula Exotarium. To a certain degree North Korean specimens are a kind of an intermediate variation between Chinese and Far Eastern variations of Chersky complex. From their Chinese neighbours they differ by a darker colouration in some cases containing greenish – brown tones and, in their turn, they have some features of the Far Eastern population.

Dark Yellow is a working name which we use for several years as a commercial name.

Selective bred variations

In connection with the fact that selective work with Dione rat snake was initiated relatively recently, many genetic lines are not fixed and give segregation in the offspring. At present we are making a regular work on their fixation that is why we give only a brief description.

Chinese Sun

Variation selected by Rainer Fesser from Chinensis specimens is characterized by a rich bright-yellow tint in the colouration. Previously we used a working name Bright Yellow, but at present it is changed into a more expressive Chinese Sun.

Red (Red Blotched)

Received from a female of Chersky which has in its colouration elements of red and pink, Red is the first variation of E.dione bred in captivity. The colouration consists of red and yellow tones with red-brown blotches and longitudinal stripes. The name Red Blotched is used as a variant which reflects more precisely the scheme of the colouration and pattern.

S-red Striped

Super Red is characterized by a bright practically orange colouration with brown stripes contrastingly prominent on its background. Characteristic blotches running over the stripes are absent in this case. It is surely a most stable variation which gives in its offspring practically monotypic specimens.

Orange

One of the most attractive variations in the group of Dione rat snakes which has an even orange-red colouration. Characteristic for the species stripes and blotches completely disappear in the normal condition of the animals becoming weakly marked only in the periods of shedding.

Lemon

Variation characterized by a bright yellow tint in the colouration and practically disappearing yellow-brown stripes which become more clearly defined in the periods of shedding.

Striped

At present at Exotarium are kept only specimens received by a selective way, though a similar variation is not uncommon also in the wild and is known from different parts of the distribution range – South Russia, Altai, Eastern Kazakhstan (Ryabov, pers. comm.).

Striped in our collection is one of the most diverse in outer appearance variations. These are ash-grey with practically white stripes, and yellow with dark-brown stripes, and grey with red-brown stripes specimens.

Other

In 2004 when mating of Chersky Tiger and Lemon we received a specimen with an interesting combination of colour and pattern – orange, with black-brown blotches of nearly regular rounded form and weakly marked longitudinal stripes. For the time being we did not classify the variation.

Conclusions

We will further continue our work on study of geographical variations, as well as on selecting of new variations and on their fixation in the herpetoculture. We sincerely hope that our article will attract attention of a wide circle of terrarium-keepers to keeping of Dione rat snake as it seems to us that this is a rather interesting species which is not inferior in anything to other objects of terrarium keeping.

Acknowledgements

The author expresses his gratitude to Sergei Ryabov (Tula, Russia) for his consulting help with writing of the article, to Dr. Rainer Fesser (Leutschach, Austria) for animals and information given by him, as well as to Wim van de Belt (Amsterdam, the Netherlands) for his interest to our work and for his invaluable help to Tula Exotarium in the sphere of development of international cooperation.

Literature

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Bakiev A.G., Faizulin A.I., 2002. Materialy k kadastru zemnovodnyh i presmykajuščihsja Samarskoy oblasti. Materialy k kadastru amfibii i reptilii basseina Srednei Volgi. N.Novgorod, Ecocenter “Dront”, pp. 98-132.

Bannikov A.G., I.S.Darevsky, W.G.Iščenko, A.K.Rustamov & N.N.Ščerbak, 1977. Opredelitel’ zemnovodnyh i presmykajuščihsja fauny SSSR. Prosweščenije, Moscow, pp. 287-289.

Borkin L.Ya., Munhbajar Kh., Orlov N.L., Semenov D.V., Terbichi Kh., 1990. Rasprostranenie reptilii v Mongolii. Reptilii gornyh i aridnyh territorii: sistematika i rasprostranenie. L.: Zool. Institute of Academy of Sciences of the USSR, pp. 22-138.

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Obst F.J. & N.N.Ščerbak, 1993. Elaphe dione (Pallas, 1773), Steppennatter. In: W.Bohme: Handbuch der Reptilien und Amphibien Europas. Aulaverlag, Wiesbaden, pp. 296-315.

Ryabov S.A., 2001. Persian Rat Snake Elaphe persica (Werner, 1913): natural history, keeping and breeding in captivity. Litteratura Serpentium, Vol. 21, No.5, pp. 137 – 142.

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Shammakov S., 1981. Presmykajuščiesja ravninnogo Turkmenistana. A.: Yllym, pp. 264-266.

Vashetko E.V., Chikin Yu.A., Khodzhaev A.F., Nuridzhanov A.S., 2003. Gerpetofauna zapadnogo Tyan-Shanja (Uzbekistan). Contemporary herpetology, Vol.2., Saratov, Publishing of Saratov University, pp. 24-39.

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