Some remarks to the distinction between
Blue-Striped Garter (Thamnophis sirtalis similis)
and
"Florida Blue" (Thamnophis sirtalis sirtalis)


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Jürgen CHLEBOWY & Martin HALLMEN
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- Translation of a published german article from J.Chlebowy & M.Hallmen -


Introduction

The common garter snake, Thamnophis sirtalis, is a widespread species in North America. It is available in numerous subspecies and color variations. An easy to keep species of snakes, it is also well known in Europe. The blue colored or blue striped ssp. are especially popular.

Both blue colored sirtalis started a lot of confusion in herpetoculture. There is the Blue-Striped Garter Snake (Thamnophis sirtalis similis) Rossman 1964 and a color variation of the Common Garter Snake (Thamnophis sirtalis sirtalis) called "Florida Blue". In all publications from Rossman (1996), Sweeney (1992), Perlowin (1994), Mara (1995) and Mutschmann (1995) they distinguish both forms, but gave no identification between Thamnophis s. similis and the color variation of the Common Garter Snake (Thamnophis s. sirtalis) "Florida Blue".
Only Mutschmann (1995) explicitly points out to be careful not to mix up both blue colored species. The following points should help provide identification of both snakes.


Dissemination

The blue-green variation "Florida Blue" of the Common Garter Snake (Thamnophis s. sirtalis) is spread throughout many parts of Florida. The problem in this species is, that they are also available in the habitat of Thamnophis sirtalis similis. The Blue-Striped Garter Snake (Thamnophis s. similis) is located in the coast area of northwestern Florida (Mara 1995, Rossman 1996). Mutschmann (1995) specifies the location from Walkulla County - Withlacoochee.


Distinction-Helps

Our observations to the distinction of Thamnophis sirtalis similis and Thamnophis sirtalis sirtalis ("Florida Blue") are based on experiences with snakes of European breeders, dealers, CB and wild caught US imports. Our observations are not within meaning of a statistical exclusion (for example: about a systematic quantitative analysis morphological features), however, they were examined by several individuals and in most cases were properly identified.


Thamnophis sirtalis similis
(Blue Striped)		   Thamnophis sirtalis sirtalis
(Florida Blue)
Body Size:
Slender snakes with average size.		 Body Size:
Strong and large snakes.
Dorsum:
Dark brown, dark gray - black.
 		 Dorsum:
Likewise dark; but in comparison
are lighter.
Dorsal Stripes:
White - white gray; relativly narrow
and not always present or interrupted		 Dorsal Stripes:
yellow; broad stripe

Lateral Stripes:
Lightblue till whiteblue; well present
on the whole body side;
delimited from dark groundcolor
of the dorsum		 Lateral Stripes:
Greenblue till green, turquois; mostly
not well delimited to the dark dorsum;
well delimited only in the first third.
 
Bar Pattern:
Does not extend to the dorsal stripe; on both
sides of the dorsal stripe are black bands
before bars and blue coloration are seen.
Zone of the bars area are very small		 Bar Pattern:
Extend to the dorsal stripe; well present
as bars; no black bands on both sides of the
dorsal stripe; Zone of the bars are very large.
 
Age Shade:
Dorsum darker in age;
Age melanism
 		 Age Shade:
Dorsum more light in age; dark coloration
changes in light green to olivgreen
 
Headforms:
Small slender head; only
little put down from the body.		 Headforms:
Long pulled strong head
clearly put down from the body.



Limit of determination

Most adult individuals are easy to identify with that assignments. But problems with identification are shown in juveniles and semi-adults of that species. Many individuals of both species looks similar in this stage of ages. Exspecially Thamnophis s. similis babies change lateral stripes from greenblue into light blue after adulthood.


Situation of both Species in Europe

Most dealers and breeders classify all available species as Blue-Striped Garter Snakes (Thamnophis sirtalis similis) by ignorance. But with our observations we found that most blue colored species, available in Europe, are Thamnophis sirtalis sirtalis ("Florida Blue"). The fact is that true Blue-Striped Garters (Thamnophis s. similis) are very rare in European collections, both in dealers and breeders. We estimate the count of real Thamnophis s. similis is less than 10% of the species that are offered as real Blue-Striped Garters.

One cause of this confusion is the difficulty of identifying both species, the other is the fact that real Thamnophis sirtalis similis are very rare and therefore they could get a much better price on the market when they offer them as real "similis". So many breeders and dealers aren't interested in a real identification of both species.

The fact is that customers should be careful in locating and buying Thamnophis sirtalis similis. However there is a comfort, Thamnophis sirtalis sirtalis ("Florida Blue") is also very attractive.

NOTE:Identification should be very important for serious herpetoculturists!!


Literatur

MARA, W.P. (1995): Strumpfbandnattern im Terrarium. - Bede-Verlag: 93 Seiten. Ruhmannsfelden.
MUTSCHMANN, F. (1995): Die Strumpfbandnattern - Biologie, Verbreitung, Haltung. - Westarp Wissenschaften: 172 Seiten. Magdeburg.
PERLOWIN, D. (1994): The General Care & Maintenance of Garter Snakes & Water Snakes. - Advanced Vivarium Systems. 71 Seiten. Lakeside.
ROSSMAN, D.A. / FORD, N.B. & SEIGEL, R.A. (1996): The Garter Snakes - Evolution and Ecology. - University of Oklahoma Press: 332 Seiten. Norman und London.
SWEENEY, R. (1992): Garter Snakes - Their Natural History and Care in Captivity. - Balford: 128 Seiten. London.


Abstract:
Übersetzung von: Einige Unterscheidungsmerkmale von Thamnophis sirtalis similis und Thamnophis sirtalis sirtalis ("Florida Blue")
Artikel von Jürgen CHLEBOWY und MARTIN HALLMEN