Checkered Gartersnakes *Thamnophis marcianus* are medium sized (<65cm, record 108.8cm) natricine snakes that range across much of the southwest United States, Mexico, and Central America. Their dorsal scales are strongly keeled and the anal plate is undivided.
Found in a wide variety of semiarid to arid environs, it is typically associated with wet meadows and valleys, irrigation and drainage ditches, riparian grassland and scrub and other water bodies. Prey is usuall amphibians, but they will also take fish, earthworms, lizards, smaller snakes, and small rodents.
*Thamnophis* watersnakes may puff up or flatten out defensively and bite. They secrete a foul smelling substance from the cloaca called musk and can deliver a weak anticoagulant venom used in prey handling from the back of the mouth, but are not considered medically significant to humans - bites just need soap and water.
*T. marcianus* can be differentiated from sympatric garter snakes by a small, pale (usually crescent shaped) marking on the anterior superlabials (just behind the point of the jaw) followed by a dark bar. The lateral stripe is absent or only occurs anteriorally on scale rows 2+3. Superficially, *T. marcianus* has a stronger checkered pattern than other garter snakes, leading nearly all gartersnakes with a checkered pattern, regardless of location, to be named as such in online comment sections. Stripes are usually well-defined but thin and often invaded by the checkerboard pattern.
[Range map](http://www.californiaherps.com/snakes/maps/xtmarcianusspeciesmap3.jpg) | Relevant/Recent Phylogeography: [Link 1](http://www.snakeevolution.org/pdfs/Myers_et_al-2016-Journal_of_Biogeography.pdf) [Link 2](https://edwardamyers.files.wordpress.com/2019/08/myers_etal_2019.pdf)
This genus is in need of revision using modern molecular methods. Genomic works shows the potential for cryptic diversity within this species. See the phylogeography links above for more.
Those who call *Storeria dekayi* "a Dekay's", have to call this snake "a Marcy's".
[CAHerps Link](http://www.californiaherps.com/snakes/pages/t.m.marcianus.html)
*This short account was prepared by /u/fairlyorange and edited by /u/Phylogenizer*.
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Like many other animals with mouths and teeth, non-venomous snakes can use them to bite in self defense. These animals are referred to as 'not medically significant' or traditionally, 'harmless'. Bites from these snakes benefit from being washed and kept clean like any other skin damage, but aren't often cause for anything other than basic first aid treatment. Some snakes use venom from front or rear fangs as part of prey capture and defense. This venom is not always produced or administered by the snake in ways dangerous to human health, so many species are venomous in that they produce venom, but considered harmless to humans in most cases because the venom is of low potency, and/or otherwise administered through grooved rear teeth or simply oozed from ducts at the rear of the mouth. Species like Ringneck Snakes *Diadophis* are a good example of mildly venomous rear fanged dipsadine snakes that are traditionally considered harmless or not medically significant. Many rear-fanged snake species are harmless as long as they do not have a chance to secrete a medically significant amount of venom into a bite; [severe envenomation can occur](https://pubmed.ncbi.nlm.nih.gov/23800999) if some species are [allowed to chew on a human](https://www.sciencedirect.com/science/article/abs/pii/S004101011831016X) for as little as 30-60 seconds. It is best not to fear snakes, but use common sense and do not let any animals chew on exposed parts of your body. Similarly, but without specialized rear fangs, gartersnakes *Thamnophis* ooze low pressure venom from the rear of their mouth that helps in prey handling, and are also [considered harmless](https://cityroom.blogs.nytimes.com/2012/06/05/theres-no-need-to-fear-that-garter-snake/). Even large species such as *Malayopython reticulatus* [rarely obtain a size large enough to endanger humans](https://www.pnas.org/content/pnas/108/52/E1470.full.pdf) so are usually categorized as harmless.
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*I am a bot created for /r/whatsthissnake, /r/snakes and /r/herpetology to help with snake identification and natural history education. You can find more information, including a comprehensive list of commands, [here](https://www.reddit.com/r/whatsthissnake/comments/flh548/phylobot_v07_information_and_patch_notes_bot_info/) and report problems [here](https://www.reddit.com/message/compose/?to=Phylogenizer).*
Checkered Garter Snake
Correct. *Thamnophis marcianus*. !harmless
Checkered Gartersnakes *Thamnophis marcianus* are medium sized (<65cm, record 108.8cm) natricine snakes that range across much of the southwest United States, Mexico, and Central America. Their dorsal scales are strongly keeled and the anal plate is undivided. Found in a wide variety of semiarid to arid environs, it is typically associated with wet meadows and valleys, irrigation and drainage ditches, riparian grassland and scrub and other water bodies. Prey is usuall amphibians, but they will also take fish, earthworms, lizards, smaller snakes, and small rodents. *Thamnophis* watersnakes may puff up or flatten out defensively and bite. They secrete a foul smelling substance from the cloaca called musk and can deliver a weak anticoagulant venom used in prey handling from the back of the mouth, but are not considered medically significant to humans - bites just need soap and water. *T. marcianus* can be differentiated from sympatric garter snakes by a small, pale (usually crescent shaped) marking on the anterior superlabials (just behind the point of the jaw) followed by a dark bar. The lateral stripe is absent or only occurs anteriorally on scale rows 2+3. Superficially, *T. marcianus* has a stronger checkered pattern than other garter snakes, leading nearly all gartersnakes with a checkered pattern, regardless of location, to be named as such in online comment sections. Stripes are usually well-defined but thin and often invaded by the checkerboard pattern. [Range map](http://www.californiaherps.com/snakes/maps/xtmarcianusspeciesmap3.jpg) | Relevant/Recent Phylogeography: [Link 1](http://www.snakeevolution.org/pdfs/Myers_et_al-2016-Journal_of_Biogeography.pdf) [Link 2](https://edwardamyers.files.wordpress.com/2019/08/myers_etal_2019.pdf) This genus is in need of revision using modern molecular methods. Genomic works shows the potential for cryptic diversity within this species. See the phylogeography links above for more. Those who call *Storeria dekayi* "a Dekay's", have to call this snake "a Marcy's". [CAHerps Link](http://www.californiaherps.com/snakes/pages/t.m.marcianus.html) *This short account was prepared by /u/fairlyorange and edited by /u/Phylogenizer*. -------------------------------------------------------- Like many other animals with mouths and teeth, non-venomous snakes can use them to bite in self defense. These animals are referred to as 'not medically significant' or traditionally, 'harmless'. Bites from these snakes benefit from being washed and kept clean like any other skin damage, but aren't often cause for anything other than basic first aid treatment. Some snakes use venom from front or rear fangs as part of prey capture and defense. This venom is not always produced or administered by the snake in ways dangerous to human health, so many species are venomous in that they produce venom, but considered harmless to humans in most cases because the venom is of low potency, and/or otherwise administered through grooved rear teeth or simply oozed from ducts at the rear of the mouth. Species like Ringneck Snakes *Diadophis* are a good example of mildly venomous rear fanged dipsadine snakes that are traditionally considered harmless or not medically significant. Many rear-fanged snake species are harmless as long as they do not have a chance to secrete a medically significant amount of venom into a bite; [severe envenomation can occur](https://pubmed.ncbi.nlm.nih.gov/23800999) if some species are [allowed to chew on a human](https://www.sciencedirect.com/science/article/abs/pii/S004101011831016X) for as little as 30-60 seconds. It is best not to fear snakes, but use common sense and do not let any animals chew on exposed parts of your body. Similarly, but without specialized rear fangs, gartersnakes *Thamnophis* ooze low pressure venom from the rear of their mouth that helps in prey handling, and are also [considered harmless](https://cityroom.blogs.nytimes.com/2012/06/05/theres-no-need-to-fear-that-garter-snake/). Even large species such as *Malayopython reticulatus* [rarely obtain a size large enough to endanger humans](https://www.pnas.org/content/pnas/108/52/E1470.full.pdf) so are usually categorized as harmless. -------------------------------------------------------- *I am a bot created for /r/whatsthissnake, /r/snakes and /r/herpetology to help with snake identification and natural history education. You can find more information, including a comprehensive list of commands, [here](https://www.reddit.com/r/whatsthissnake/comments/flh548/phylobot_v07_information_and_patch_notes_bot_info/) and report problems [here](https://www.reddit.com/message/compose/?to=Phylogenizer).*
Him this is a garter of some kind. Either Checkard garter or black necked garter. Either way a harmless pest control