T.eques is a very large and heavily built gartersnake and Conant (2003) had set the new record for T.eques (obscurus) at 121,6 cm total length. Especially female Thamnophis eques can grow very large and heavy.
Thamnophis eques obscurus, adult female, 107 cm long from Jalisco, Mexico.
In fact adult female T.eques are the largest gartersnakes I have ever seen.
The only garter snake that really grows to much larger size is Thamnophis gigas from California.
The new record for T.eques (scotti) is now set at 130,7 cm (Bol & Bruchmann, 2012).
Description of Thamnophis eques obscurus
This subspecies of T.eques has an unusual coloration for a garter snake that makes it easily distinguishable from other species.
Thamnophis eques obscurus, adult female, 65 cm long from Jalisco, Mexico.
Dorsal color is dark brown. Dorsal stripe is readily visible in the juveniles, but often is inconspicuous in the adults. Dorsal stripe is, when present, light brown in coloration.
Lateral stripes are clearly visible in most specimens: white in the juveniles but beautiful blue or grayish-blue in the adults. Also the supralabial, neck and ventral scales have this typical blue or grayish-blue color. This blue color develops while aging.The two lower scale rows (between the ventral scales and the lateral stripes) have a light nucleus with a more or less golden color and shine.
Thamnophis eques obscurus, adult male, more then 70 cm long from Jalisco, Mexico.
The spots between the lateral and dorsal stripe are sometimes prominent ( in pregnant females or just after feeding) and sometimes hardly noticeable.
As in the other subspecies of Thamnophis eques coloration is difficult to describe due to the shiny and fluorescent nature of the scales.
The overall coloration matches very well with the color of the water and rocks in lake Chapala.
The Lake Chapala Mexican Gartersnake does very well in captivity. Due to its large size it is recommended to keep them in a terrarium with a minimum size (for one adult couple) of 100 x 50 x 50 cm. They do well in a dry and well ventilated cage with just a water bowl for swimming and drinking. The water bowl should be big enough for them to submerge in. Local temperatures in the terrarium should rise to 30-35 °C. T.e.obscurus are voracious feeders and relatively easy to keep.
Newborn juveniles of Thamnophis eques obscurus.
They tend to be relatively shy but most(especially the captive bred) specimens often lose much of their shyness when they grow older. The snakes show themselves a lot basking on a branch under the lamp. Especially when the terrarium is not so warm and the snakes need to bask on the hottest spot to reach their optimal body temperatures. A hibernation will not be absolutely necessary although it is expected that they will have a resting period in nature when they are less active. A cool period in the terrarium of 2-3 months will probably be sufficient to keep the snakes in good health and to stimulate breeding. Up to now I hardly give the snakes a hibernation. But the snakes are clearly less active in the coldest winter months; they bask less and often refuse to eat for several months. So do not worry when this happens. Night temperatures in my snake room (and in the terrariums) drop at night to 8-12 °C. I keep my adult snakes in a completely dry terrarium with a water bowl. This species is also very suitable for a so-called “aqua-terrarium” with a lots of water and only a small (completely dry!) land part which is heated by a powerful lamp to 30-35 °C. In such a habitat terrarium the highly aquatic snakes will show more of their natural behavior.
The young are usually born in my terrariums in June or July.
Sometimes females have a second clutch in October.
Distribution and habitat of T.e.obscurus
Thamnophis eques obscurus occurs only in Lago Chapala.
Habitat of Thamnophis eques obscurus in November 2007, Jalisco, Mexico.
Willow tree with sunning and mating Thamnophis eques obscurus in May 2008, Jalisco, Mexico.
This large endorheic lake lies in the Mexican states of Jalisco and for a small part in Michoacán at 1525 meters above sea level. It is the largest lake in Mexico: 80 km long and 20 km wide.
In November 2007 and May 2008 I have observed this subspecies at Lake Chapala. The snakes can be found on the rocky borders right at the water’s edge or swimming in the lake itself. Like Nerodia these large Garter Snakes swim floating on the water.
“Mating ball” of Thamnophis eques obscurus in May 2008, Jalisco, Mexico.
In May 2008 I found large numbers of this subspecies sunning and mating in the willow trees that grow at certain places in the lake.
For more details read my article (Bol, 2010 (26)), and the movie with unique recordings of mating behavior in the wild.
My breeding group consist of offspring of 5 adult (unrelated) wild caught specimens. This gives me the opportunity to have young that are completely unrelated.
Thamnophis eques obscurus, adult male swimming in the Lake of Chapala in November 2007, Mexico.
Which is perfect for future breeding programs.
I am breeding this subspecies since 2009.
Literature: Bol, S., 2010. Exciting observations on two sympatric garter snakes in “la Laguna de Chapala”, Mexico. ( Part 1 of 2). The garter snake 15 (1): 16-27. Bol, S., 2010. Exciting observations on two sympatric garter snakes in “la Laguna de Chapala”, Mexico. ( Part 2 of 2). The garter snake 15 (2): 10-19. Bol, S. & H. Bruchmann, 2012. Scott’s Mexican Garter Snake (Thamnophis eques scotti; Conant, 2003) in the wild and in captivity. ( Part 1 of 2). The garter snake 17 (3): 15-25. Bol, S. & H. Bruchmann, 2012. Scott’s Mexican Garter Snake (Thamnophis eques scotti; Conant, 2003) in the wild and in captivity. ( Part 2 of 2). The garter snake 17 (24-31): 16-27. Conant, R., 2003. Observations on Garter Snakes of the Thamnophis eques complex in the Lakes of Mexico’s Transvolcanic Belt, with descriptions of New Taxa. American museum novitates 3406: 1-64.