| 1 | Common garter snake |
Latin: Thamnophis sirtalis.
Range: all lower 48 states excluding Arizona, most of southern Canada.
The garter snake which all others are judged against. The common garter snake is the most widespread reptile, not just snake, in the whole of North America. It inhabits all states except parched Arizona, and is the sole snake in the frigid Northwest Territories (NWT) region of Canada. It may, just may, reach southeastern Alaska (still unconfirmed).
For reasons nobody knows, common garter snakes can cope with far more varied habitats than their cousins. Thick forests, town gardens, and rocky shrubland are acceptable. Nevertheless, their favourite spots are undoubtedly grassy meadows not far from streams or ponds. These moist zones are home to their favourite prey, amphibians and earthworms. Common garter snakes are non-aggressive, but manufacture toxins in their saliva, which can surprise bite victims with their strength.
Common garter snakes coexist with virtually all other species on this list, as though it’s the main garter snake from headquarters supervising all the smaller ones, which have been handed smaller slices of territory. Common garter snakes also have 13 varying subspecies, including the red-sided garter snake, which has blue tinges. However, this article will only cover full species of the garter snake family (Thamnophis).
| 2 | Eastern ribbon snake |
Latin: Thamnophis sauritus.
Range: eastern USA, Ontario.
While possessing a fancier name, this is undoubtedly a true member of the Thamnophis garter snake family. Eastern ribbon snakes are a water-loving species, commonly appearing in streams of Ohio, Pennsylvania and New York state. They have many survival tricks up their sleeves, such as shifting warmth from their tail to their bodies in cold weather, and climbing 6 metres high into riverside branches to dodge sudden floods.
Many riverside dog walkers have confused this snake, but this is one of the easiest garter snakes to distinguish. Their belly tends to be paler than the common garter snake, and their faces are cleaner, with less markings. Eastern ribbon snakes are also the thinnest Thamnophis member, and have a signature white dot in front of each eye.
Eastern ribbon snakes source over 90% of their calories from amphibians, with a helping of caterpillars and fish. The northern leopard frog is their favourite prey. Eastern ribbon snakes use neither venom nor constriction, grabbing a frog and swallowing them down in whatever clumsy way possible.
| 3 | Aquatic garter snake |
Latin: Thamnophis atratus.
Range: California, Oregon.
The name is slightly misleading, as Thamnophis atratus is no more aquatic than the giant garter snake. Nevertheless, they commonly swim in streams, ponds, and marshes along the west coast of California and Oregon where they reside. At least 80% of their diet consist of frogs and toads, the rest salamanders, and they’re able to use their tongues to mimic insects, poking it just below the water surface to attract curious fish.
Aquatic garter snakes are easy to identify. They’re often completely missing the stripes on their sides, and the yellow stripe down their spine is thicker and blotchier than usual. This is a medium length garter snake, with a record of 14cm.
A study from Saint Lucia Preserve showed how the family compares. 3 garter snakes lived side by side, and the local aquatic garter snakes were always found 1 metre from a pond. The common garter snakes stayed 20 metres away from pond edges, while the terrestrial garter snakes were found hiding under cover in grassy fields, 50 metres away the nearest water.
| 4 | Terrestrial garter snake |
Latin: Thamnophis elegans.
Range: western USA, southern Canada.
The second most sprawling garter snake after the common one, occupying 14 states, just reaching far western Oklahoma and Nebraska. Terrestrial garter snakes are extremely flexible and can inhabit grassy fields, forests, streams and rocky shrubland. Their diet is the most varied out of any garter snake, shifting effortlessly within one location. In one river, the local Thamnophis elegans ate 56.2% crayfish, with a side helping of voles, while in Saint Lucia Preserve in Monterey County, California, mammals made up 82% of their diet. Yet another dataset found that fish made up 38%, frogs and toads 23%, and mammals just 2%. Either way, the terrestrial garter snake is much more likely to eat mammals than other Thamnophis snakes. The common garter snakes in Saint Lucia Preserve ate no mammals at all.
This species is tricky to distinguish from common garter snakes, but have a larger saliva gland and several scale differentiations. They’re also smaller than the common garter snake, with a record length of 107cm versus 134cm. The two have a large genetic chasm between them.
Thamnophis elegans is the most likely garter snake to constrict its prey, and their venom also seems particularly severe. They’re don’t come close to an Egyptian cobra, but one prolonged bite resulted in swelling, pain and local haemorrhaging.
| 5 | Giant garter snake |
Latin: Thamnophis gigas.
Range: California.
The largest garter snake of the USA, but also the most endangered. Giant garter snakes can reach 162.6cm, and inhabit the Sacramento and San Joaquin valleys of California. As of 2022, just 10% of their 19th century ranges remain. They’re a strongly aquatic species which once roamed freely around unending marshes, which have long since been absorbed by agriculture. Their only saving grace is that Sacramento is covered with rice paddies, which are semi-flooded and have numerous water drainage channels, a perfect mimic of their true habitat.
Giant garter snakes correlate closely with one plant: strands of tule. Their favourite marshes are ones with heavy borders of vegetation, but also gaps they can slither through, to inspect dry land. Giant garter snakes have the sneaky skill of slithering through water culverts and crossing busy highways. Their diet relies heavily on frogs, including the Sierran tree frog, with a side helping of fish. Giant garter snakes are mostly lethargic, but can slither up to 5 miles in a few days when on a quest for new territory.
| 6 | Northwestern garter snake |
Latin: Thamnophis ordinoides.
Range: Washington, Oregon, northern California.
This garter snake is one of the most variable in colour, as red, blue, orange and green striped versions can be found within the same field. Northwestern garter snakes are relatively short, averaging at 40cm and reaching a maximum of 95cm. They also have a smaller head than most, with the same red tongue as usual. They’re one of the least aquatic garter snakes, appearing in water occasionally, but mostly sticking to open fields on the edges of forests.
Even the pattern itself varies with this garter snake, and scientists have found that this correlates with personality. Striped versions are more likely to flee in a straight line, while those with spots or no patterns dart to the side and then pause, seeking camouflage. Northwestern garter snakes eat small, slimy creatures, the kind that destroy your garden crops: slugs and earthworms. Two of their favourite species are the banana slug and dew worm.
A difference to the common garter snake is that they often have vivid red spots on their bellies. Northwestern garter snakes are also found in southwestern British Columbia.
| 7 | Sierra garter snake |
Latin: Thamnophis couchii.
Range: California, far western Nevada.
This Californian garter snake is easily one of the most recognisable. They have one of the blackest bodies, with an undercurrent of vivid orange, and the usual spine stripe is as thin as a pencil line.
Thamnophis couchii is one of the more aquatic garter snakes. As hatchlings, they hunt in shallower water, before moving to the deeper river centres as adults. One of their favourite foods is newborns of the Pacific giant salamander, and a large chunk of their diet comes from fish. This garter snake has also evolved resistance to the orange-bellied newt (endemic to California) and its deadly tetrodotoxins.
Sierra garter snakes have a reputation for aggression in captivity, meaning that they’re rarely kept. Keepers have tried and failed to get them attuned to rodents, even tempting them with artificially swabbed scents. Sierra garter snakes can be found in high mountain streams in the Sierra Nevada. Elevations of 2440 meters have been confirmed, but there’s rumours of snakes at 2500 metres in El Dorado county.
| 8 | Short-headed garter snake |
Latin: Thamnophis brachystoma.
Range: New York, Pennsylvania.
This species has an extremely narrow range among US garter snakes. New York state and northwest Pennsylvania are their sole natural bases, with introduced populations in southern Pennsylvania. Within those ranges, they’re very common, but they suddenly disappear on the outskirts, despite no change in habitat type.
Short-headed garter snakes tend to live in meadows, and occasionally forests adjacent to them. They’re shier than average, and hide under rocks and wood. Being a small garter snake, at just 36.7cm for males and 41.8cm for females, most of its diet consists of earthworms. The record is a mere 55.9cm.
This northeasterly species is easily confused with common garter snakes. However, as you’d expect, the head is the easiest separator. It’s extremely tiny in Thamnophis brachystoma, measuring just 4.3% of its body length. Unlike the common garter, the head is barely larger than its neck, carrying on like a tube. Short-headed garter snakes also look very “clean”. They have a pale stripe down their spine and on each flank, but between them, there are no scattered markings, just a neat and consistent brown colour.
| 9 | Plains garter snake |
Latin: Thamnophis radix.
Range: central northern USA and southern central Canada.
The plains garter snake is the most similar to the common, the trickiest to distinguish by appearance. They inhabit states like Ohio, Wisconsin and Minnesota, and spill well across the Canadian border. Plains and common garter snakes are regularly found metres from each other in the very same fields. Their daily pattern is similar, moving most between 1-3pm, and they stick close to water without being fully aquatic. Even their diet is extremely similar, relying on amphibians with a 5-10% helping of earthworms.
Yet the two are completely genetically separate, as they never interbreed and produce hybrids in the spots where they coexist. There are clearly differences which science hasn’t pinpointed yet, and the main confirmed one is that plains garter snakes are less flexible in their habitats, while common garter snakes can inhabit virtually anywhere except deserts. A study in Ohio found that common garters are more common in forests, while Thamnophis radix preferred wet prairies.
The physical differences are only subtle, but the Plains garter snake has a more strongly orange stripe down its spine. The inbetween scales are also darker on average.
| 10 | Butler’s garter snake |
Latin: Thamnophis butleri.
Range: northern USA, Ontario.
Butler’s garter snake is one of the shorter species, with record female length of just 73.7cm. Their other characteristics, however, are nearly impossible to separate from common garter snakes. The only hope is their pale side stripes. In common garter snakes, these are centred on the 2nd and 3rd rows of scales above their bellies, while in Butler’s garter snake, they’re centred on rows 3 and 4.
Butler’s garter snakes live in wet meadows and tall grass prairie, often taking refuge in the burrows of chimney crayfish. They have the usual liking for moisture, but prefer open areas rather than forests. They move an average of 14 metres per day, accelerating during summer. Butler’s garter snakes almost never swim in rivers or lakes, but like to hide in 8 inch high vegetation on their borders. Consequently, Butler’s garter snake can use these as a corridor to infiltrate towns. They’re one of the more suburban-friendly, and are sometimes found under scattered rubbish in vacant lots.
Nowadays, Butler’s garter snake gets 83% of its calories from earthworms, which aren’t native to the USA. They likely ate slugs before they were introduced.