Scott’s Mexican Garter Snake (T. eques scotti, Conant, 2003) in the wild and in captivity.
Steven Bol & Herbert Bruchmann
Steven Bol, Honselersdijk, The Netherlands (www.stevenbolgartersnakes.com)
Herbert Bruchmann, Hellehohlweg 34. 59929 Brilon, Germany
(Vertaling in het Nederlands volg nog…)
Dorsally the snakes have a light coloration (yellow, light brown, pale green) and typical is their unusually wide middorsal stripe which can cover up to 7 scale rows. Conant (2003) called these snakes “blonde” in coloration. The yellowish or brownish-yellow middorsal stripe can have the same color as the remainder of the body so that it sometimes looks like the snakes are virtually stripe less. But in darker specimens the middorsal stripe is clearly visible. There is no black line bordering the middorsal stripe.
The lateral stripes are more prominent and much lighter in color. They can be anywhere from white to yellow to greenish, sometimes almost bluish green.
There are usually 2 rows of black spots between the rows which can vary in size and may be more or less inconspicuous. They can also be quit big and very prominent. The higher row of spots sometimes partially invade the dorsal stripe.
The labials often have the same light color as the lateral stripe and are in contrast with the darker upper part of the head. The yellow labials have beautiful black sutures. Lower labials and chin also light colored, mostly yellow. Nuchal blotches often vague in the adults, but they can be quite prominent in the juveniles. Behind the head they have a light yellow ring in the neck, somewhat like the European Grass Snake (Natrix natrix). The 2 rows of scales below the lateral stripes are usually lighter colored then the dorsal scales. Belly is grayish-green and more or less without any pattern. Conant (2003) mentions the huge variability within this population as typical for this subspecies. But in general this snake is unusually light colored in a unique way, very unlike any other species of garter snake.
Thamnophis eques is one of the largest Garter Snake species and Conant (2003) mentions a new record total length for T.eques (obscurus) of 121,6 cm. Especially the females become fairly large and stout bodied. Older and other literature (almost exclusively based on the American populations of T.e.megalops state this is a “medium sized garter snake reaching one meter in total length” (Greenwald, D.N., 2003) or a “medium sized snake reaching a total length of 112 cm (Brennan, T.C. and A.T.Holycross, 2009). When we first encountered Thamnophis eques scotti in the wild we could not believe how huge most specimens where in Lago de Magdalena. The first author (S. Bol) found a huge old female that would have been 130,7 cm total length with a complete tail (part of the tail was missing). A new record for this species!
Observations in the wild
August 3rd – 6th 2007 the second author (Bruchmann) visited Lago de Magdalena.
August 3rd was a hot day with temperatures at 2 pm of 36,2 ºC. At 8 PM it was cloudy but temperatures were 25,9 ºC. No snakes were seen.
The next day, August 4th 2007 the habitat was explored from 07.30 AM onwards.
It had rained during the night. About 20 adult T.e.scotti were seen swimming in the lake close to the embankment. One large female (possibly pregnant) was seen high on the embankment. After 10 AM hardly any snake activity; it was probably too hot.
No amphibians were seen but 2 frogs were heard calling in the nearby swamp.
August 5th it was cloudy and windy. No snake activity.
August 6th 2007 it rained again during the night. It was not as hot and it was cloudy. The habitat was explored from 07.30 onwards. The first adult scotti was seen at 08.30 AM high on the embankment. Eight others were seen swimming in the lake. The snakes made sure they swim around the observer, which means they have good eyesight. And which makes them very difficult to catch in the warm weather. At 10 AM temperature was 24,7 ºC in the air; water temperature measured 1 meter deep was 26,4 ºC.
November 11th 2007 the first author (Bol) visited Lago de Magdalena. Night temperatures were around 5 -10 ºC, but daytime temperatures rose up to appr. 30 ºC (no exact measurements).
The habitat was explored from 1 – 5.30 PM. Being in the habitat makes one realize that microhabitat, climate and behavior of the snakes are in a complex way interacting. The snakes probably prefer the embankment with large boulders and vegetation since it provides a safe place to bask; the open spaces between the large boulders provide ample hiding places and the vegetations helps to thermo regulate in a safe way. From the embankment they have a safe excess to the lake. The habitat on the embankment with the large boulders is on a steep sloop facing north. With the low November sun the boulders were in the shadow and still felt cold at 1PM. The only place where the snakes can bask to reach their preferred body temperature in this time of the year around 1 PM is on top of the embankment or in the lake floating on the water.
In the first 30 minutes 3 snakes were seen basking high on the embankment. Two got away, but a third one was a large female of 91 cm total length (71cm snout-vent length (SVL) and 20 cm tail length (TL)). The snake had recently eaten a large fish.
The first snake was observed swimming. It was a great challenge to catch the swimming snakes. In the next 30 minutes 3 huge females were caught; all more then 100 cm total length. All 3 were in the water. One of them had recently a fish. 1 of the females was extremely huge and thick. She was 100 cm SVL with a broken tail of 10 cm. With a relative tail length of 23,5 % (some females even have slightly longer tails) she would have measured approximately 130,7 cm. This is a new record for this species and subspecies. The old record was 121,6 cm for Thamnophis eques obscurus (Conant, 2003).
Thamnophis eques scotti swims with it’s body floating on the water. Some snakes were observed swimming, other were floating on the water close to the embankment (close to the large boulders). Possibly this is a way for the snakes to thermo regulate in a safe way. Of course this needs confirmation via extra observations but basking on the water (other then on algae mats) has not been mentioned in literature about Garter Snakes.
After 2.30 PM the sun started to shine on the lowest rocks near the water; higher on the embankment the boulders still felt very cold and were still in the shadow. Towards the end of the afternoon there was a bit more sun on the lowest rocks of the embankment, but at no time the sun was really strong on the embankment. Possibly this is the case in the early morning hours though.
Anyway the snakes became very quick and agile between 3 and 4.30 PM and hence difficult to catch.
A nice observation concerned a large specimen that was swimming in the lake around 5.15 PM. The wind started to catch up and temperatures started to drop. Obviously the snake did not notice the observer and returned to the embankment, crawled on one of the lower rocks and started to bask in order to catch the last rays of the sun that was dropping fast.
Between 2.30 and 5.15 PM a total of 11 adults T.e.scotti were caught, of which 2 were males. The 2 males were 84 and 85 cm TL, the females measured 87 – 113 cm TL. Two of the snakes had recently eaten. Also 1 male Mexican Blackbelly Garter Snake (T.melanogaster canescens) was found.
November 21st 2009 the first author (Bol) visited Lago de Magdalena again from 12.45 – 5.00 PM. Temperature was 25 °C upon arrival and the sun was shining.
The snakes were very active. Approximately 70 different snakes were seen or heard. Approximately three T.m.canescens, but the majority was T.e.scotti. Most of them were sunning, a few were seen swimming.
Several times this day 2 – 5 snakes were observed together, but since they were very agile and fast due to the high temperatures they more or less disappeared on sight. On one occasion 2 – 3 snakes disappeared down the embankment where they refrained from escaping into the water. Instead they were obviously searching and looking around (for a mate?) and 2 snakes climbed up the embankment again. One of the snakes that crawled up was caught and proved to be male. This typical behavior (males that do not try to escape after disturbance but quickly try to locate the female again) was also observed the same morning at Lago Chapala (Bol, 2010). Here a small mating ball of courting T.eques obscurus (4 males with 1 female) was found in a patch of reed. Because of the combined observations the first author (Bol) is convinced that also Thamnophis eques scotti was actively courting on November 21st 2009.
January 30th 2010 the first author (Bol) visited Lago de Magdalena from 12.35 PM until 5.10 PM. It was a sunny day with shattered small clouds. Towards 5 PM the sun disappeared behind the clouds. Maximum temperatures probably 27 – 29 ° C.
Like November 21st 2009 there was a lot of Garter Snake activity. In total approximately 45 – 50 snakes were seen. 5 of them were T.m.canescens, all sunning between the rocks close to the water. The majority were large T.e.scotti all basking in the warm January sun. Only 1 snake was seen swimming. Several snakes had recently eaten and looked well nourished. Some of the females were so thick that they seemed to be pregnant, although this could not be confirmed through palpation. Many recently shed skins could be found between the rocks, and some snakes were about to shed their skins. Some snakes were caught for measurements; 4 males of 71, 76, 96 and 102 cm total length; 3 females measured 93, 99,5 and 103 cm total length.
I found 2 snakes (T.e.scotti) lying dead on the rocks. One small male scotti was severely injured but still looked surprisingly healthy. One very old female had a large scar on her back as large as a 1 euro coin.
The last scotti was observed that day sunning at 5 PM.
Our observations in August & November 2007, November 2009 and January 2010 show that Thamnophis eques scotti is still occurring in high quantities in the lake of Magdalena. The observations in August are in line with Conant’s observations (Conant, 2003). It is very likely that the snakes are active from August onwards well into November. Our observations in early and late November and in January suggest that Thamnophis eques scotti remains active throughout the winter. Perhaps activity slows down when the lake dries up in May or June.
Both authors do not really hibernate T.e.scotti, but have kept them warm throughout the winter in most years.
Bol keeps his snakes in a unheated room in the attic. Night temperatures can drop to 8 – 12 °C in December and January during cold spells. So the snakes will notice it is winter. The snakes are not very active during the winter months and eat less frequently. Sometimes they refuse to eat for a few weeks (6 – 10 weeks) in a row. They do bask infrequently, sometimes only for a few hours per day. Other days they stay in their hiding places or they lay practically motionless for days or weeks in a row in the waterdish. Especially when temperatures are very low they retreat in the water.
Bol has also offered both adults and babies in 2011 a short hibernation of 4 – 10 weeks. Some snakes remained in their terrariums at 10 – 15 °C, simply by keeping the lights switched off. The snakes can also handle such a short hibernation without problems. A few snakes were kept colder in small container with wet substrate and 100 % RH for 8 weeks at temperatures that dropped even as low as 2 °C. This is how Bol hibernates all his American and Canadian Garter Snake species. The snakes came out of this hibernation looking fit and healthy.
Bruchmann simply lowers the wattage of the lamps in wintertime and shortens the time they are switched on.
Our conclusion is that T.e.scotti does not need to be hibernated, and low night times during wintertime mimic the natural situation in Mexico. One can choose to hibernate T.e.scotti for a relatively short period without any problems though, and in Mexico cold spells of 1 – 2 weeks during wintertime will occur.
The snakes differ a lot individually as far as behavior in captivity is concerned. The young babies tend to be quite shy in general. They like to hide under cover and disappear quickly when you enter the room.
Bruchmann has a wildcaught male which has remained very aggressive and will bite when handled. Another captive bred male and the wildcaught female are quite shy but can be handled with quiet and slow movements. One captive bred female is very tame and can be handled without problems.
Both the wildcaught as the captive bred adults of Bol are quite tame and can be handled without being bitten.
Outside the winter the (sub)adults are usually clearly visible in the terrarium basking on a warm spot, and they do not disappear when one enters the room.
T.e.cuitzeoensis (the subspecies occurring in Lago Cuitzeo) for instance is much more aggressive for instance and also remains more shy.
The juveniles are separated from their parents after birth and put in a small terrarium in groups of 10 or more. In general they are very easy to raise. They accept dead fish or even baby mice (Bruchmann) very readily, and most juveniles start eating within 1 – 2 weeks after birth. They can grow up very fast, even on a diet of only fish fed once every 3 – 7 days. Of course growing speeds will even increase when they are fed baby mice or rats. One juvenile female bred and raised by Bruchmann reached the 94 cm after 13,5 months. One female bred and raised by Bol measured 95 cm after 15,5 month on a diet of fish only (the 15,5 month includes a hibernation of 4 weeks).
A nice indirect example of the enormous growth speed one can find in the article about T.e.scotti from Di Giandomenico (2011), where he mentions that he could not believe his snakes acquired in 2010 could have been born in 2008. The growth speed of T.e.scotti is simply very exceptional for the genus of Thamnophis.