Observations by charetej

Scientific & Common Names
The eastern garter snake, Thamnophis sirtalis sirtalis, was first described by Carl Linnaeus in 1752. The name Thamnophis translates from Ancient Greek as “bush snake”, from the words “thamnos”, meaning bush, and “ophio”, meaning snake. The name sirtalis is derived from the New Latin word “siratalis”, meaning like a garter, in reference to the snake’s striped pattern resembling that of a striped garter strap. (Krulikowski, 2004) Commonly, the species is known as the eastern garter snake due to its geographic range covering a large portion of the eastern areas of North America. It lies in the genus of common garter snakes (Thamnophis sirtalis), so named for its widespread distribution and relative abundance.
Habitat & Geographic Range
The eastern garter snake, as its name implies, is found over a very wide area on the east portion of North America ranging from the Atlantic coast west to the Mississippi River, and from Southern Ontario all the way to the Gulf of Mexico. (wscu.edu, 2016) Within this range, the garter snake is able to thrive in a wide range of habitats, though it prefers moist locations and tend to be more common near water. It can be found in forests, marshes, pastures and even in urbanized areas. Hibernating sites are generally found in well-drained grassy areas, and so during the spring a larger proportion on garter snakes will be found there. They frequently rest under rocks, fallen trees, in bushes, or other such cover where they may remain hidden and cool, especially on hot days. (Carpenter, 1952)
Size/Weight and Lifespan
Eastern garter snakes are of similar size to all other species of common garter snakes, having an average adult length of about 88cm, with a range of between 46cm to 137cm (highest recorded length). Average adult mass is about 150g. They reach the lower end of this size, approximately 55cm, when they reach sexual maturity at two years of age (1.5 for males) and continue growing throughout their lifespan. As with many other reptiles, eastern garter snakes have a high rate of juvenile mortality due to predation, leading to most individuals dying in their first year and causing a low average lifespan of about two years. In captivity, however, individuals typically live between six and ten years, with the oldest recorded common garter living to twenty. (Zimmerman, 2013)
Diet
Eastern garter snakes are carnivorous and have been found to feed primarily on earthworms, with one study by Charles Carpenter, cataloguing the digestive contents of multiple snakes, showing an 80% presence of earthworms. Other foods include amphibians (15%, mostly frogs and toads) and occasional mammals, fish, caterpillars, and leaches. Larger snakes (length greater than 40cm) were more likely to prey upon mammals and amphibians than smaller snakes, though earthworms still constituted 76% of their diet. Generally, an eastern garter snake will eat anything it can overpower and swallow. (Carpenter, 1952)
Reproduction & Communication
Because these snakes are non-communal, communication between individuals is entirely absent with the sole exception of courtship during the spring mating season. Outside of this setting, eastern garter snakes will ignore each other and other species of snake, even in close proximity. (Carpenter, 1952) Skin contact was found to be important in sexual recognition in an experiment by James Gillingham and John Dickinson, and courtship does not require head-head orientation of the male and female as in many other snakes; males may court and mate with females by signals sent through skin contact. This is due to the common garters’ mating in a “mating ball”, wherein males will clump in order to attempt to mate with a female who has just emerged from hibernation. Because, in such a circumstance, a one on one meeting between a male and female is highly unlikely, males must be able to communicate their desire to mate to the female with only a limited amount of body contact as this is the most that any individual male is likely to get. (Gillingham, Dickinson, 1980) All common garter snakes are ovoviviparous, meaning that the eggs are held in the female until ready to hatch and the young are born live, at 12.5cm to 23cm long and in litters of ten to forty. After being born, the mother provides no care or protection to her young.
Predation
Due to the eastern garter snake’s small size, it is prey to many larger mammals and birds. This is especially true for juveniles, who are less able to defend themselves and therefore suffer high mortality rates due to predation. Common garter snakes are fairly unable to defend themselves against predators due to their size and lack of venom. Though they have slightly toxic saliva, it is unable to significantly affect attackers. Most will attempt to flee from an attack, however several factors influence whether an individual will react aggressively to a potential predator. It has been found that warmer snakes are more likely to react aggressively (Schieffelin, de Queiroz, 1991), as are individuals who have just eaten, as eating makes movement, and therefore flight, more difficult but increases endurance and therefore the ability to defend from a predator. (Herzog, Bailey, 1987) Interestingly, one anti-predator defense present in common garter snakes is the ability to absorb toxins from prey (namely the rough-skinned newt) and thereby become poisonous to predators, particularly birds, deterring attack. (Brodie, Brodie, 2004)
Conservation Status
The eastern garter snake is very widespread and common, and is therefore listed by the IUCN as Least Concern.
Fun Fact
Did you know that some eastern garter snake males secrete female pheromones to attract other males to form a mating ball, and in doing so steal the heat of rival males and increase the odds of successful mating with future emerging females while reducing the odds of conflict with stronger males? In fact, these males are the most successful in mating. (Mason, Crews, 1985)

References
Krulikowski, Linda. “Snakes of New England”. Lebon Press, 2004, pp. 72–84.
“Thamnophis sirtalis sirtalis (Linnaeus, 1758) - Eastern Garter Snake”. Wscu, http://people.wcsu.edu/pinout/herpetology/tsirtalis/frame2.htm. Accessed Oct. 22, 2016
Carpenter, Charles C. “Comparative Ecology of the Common Garter Snake (Thamnophis s. sirtalis), the Ribbon Snake (Thamnophis s. sauritus), and Butler's Garter Snake (Thamnophis butleri) in Mixed Populations”. Ecological Monographs, vol. 22, no. 2, Wiley, Oct. 1952, pp. 235-258

Zimmerman, Ryan. "Thamnophis sirtalis". Animal Diversity Web, http://www.biokids.umich.edu/accounts/Thamnophis_sirtalis/. Edited by Allison Poor, Randall L. Morrison, Western Maryland College, 2013. Accessed October 22, 2016
Gillingham, James C.; Dickinson, John A. “Postural orientation during courtship in the eastern garter snake, Thamnophis s. sirtalis”. Behavioural and Neural Biology, vol. 28, no. 2, Central Michigan University, Feb. 1980, pp. 211-217
Schieffelin, Cyntia D.; de Queiroz, Alan. “Temperature and defense in the common garter snake: warm snakes are more aggressive than cold snakes”. Herpetologica, vol. 47, no. 2, Allen Press, Jun. 1991, pp. 230–237
Herzog, Harold A.; Bailey, Bonnie D. “Development of antipredator responses in snakes: II. Effects of recent feeding on defensive behaviors of juvenile garter snakes (Thamnophis sirtalis)”. Journal of Comparative Psychology, vol. 101, no. 4, American Psychological Association, Dec. 1987, pp. 387-389
Brodie ED III; Brodie ED Jr. "Tetrodotoxin resistance in garter snakes: an evolutionary response of predators to dangerous prey". Evolution, vol. 44, no. 3, pp. 651–659
Mason RT.; Crews D. “Female Mimicry in Garter Snakes”. Nature, Jul. 4, 1985, pp. 59-60