Almost everyone can identify a “garter snake” in Wisconsin!
But here’s the problem:
There are multiple species and sub-species of garter snakes! Therefore, figuring out the identity of the SPECIFIC snake you are observing can be challenging. This is especially true since many of them have similar appearances and behaviors.
Today, you are going to learn about 5 garter snake species in Wisconsin!
- *Just a quick note – to be officially considered a garter snake, the species must be in the genus Thamnophis*
#1. Eastern Garter Snake
- Thamnophis sirtalis sirtalis
- Adults typically range from 18 to 26 inches in length.
- Coloration varies and can be mixtures of green, brown, or black. Look for a distinct yellow or whitish stripe down the center of their back.
- Some individuals may exhibit a checkered body pattern.
- Subspecies of the Common Garter Snake.
Eastern Garter Snakes are common and easy to locate in Wisconsin!
In fact, they are typically the snake species that people come across the most. They are well-adapted to living around people and can often be found in city parks, farmland, cemeteries, and suburban lawns and gardens. Though it’s not required, they prefer grassy environments near freshwater sources such as ponds, lakes, ditches, and streams.
Look for these garter snakes in Wisconsin basking in the sun in grassy areas near cover.
Eastern Garter Snakes will protect themselves if they are cornered or feel threatened. For example, if you capture or continually disturb one, it will defecate and release a foul-smelling musk from glands. It’s also common for them to bite as a last resort!
The Eastern Garter Snake most commonly preys on toads, frogs, slugs, salamanders, fish, and worms. However, they are very opportunistic and will eat other insects and small animals they can overpower. They’re active during both the day and night, depending on the temperature.
These garter snakes have a high birth rate (up to 50 babies!) and adapt well to human-disturbed habitats! Because of these traits, this species is not threatened and is relatively common and widespread.
#2. Western Ribbon Snake
- Thamnophis proximus
- Adults range from 17 to 50 inches in length. A slender snake with a long tail!
- Coloration is blackish, brown, or olive with three light-colored stripes; one down the back and one down each side.
- The sides and top of the head are dark, and the upper lip is whitish.
Did you see a slender garter snake in southern Wisconsin with a long tail?
If so, it was probably a Western Ribbon Snake! This semi-aquatic species is rarely found far from a water source. They typically occupy brush-heavy areas around streams, lakes, ponds, and other water bodies. You may also spot them basking on rocks, flat vegetation, and dry sandy areas near water.
The Western Ribbon Snake has an incredible, unique hunting technique. As they move over land, they make quick, light thrusts of their head and upper body in different directions in sequences of three. It’s similar to a strike, but with their mouth closed. This action disturbs resting frogs, which alerts the garter snake to their location. From there, the ribbon snake uses its superior speed to catch its prey.
If they feel threatened, this species will flee into the water or hide in thick brush. Their coloration provides superb camouflage in dense, brushier areas. If grabbed, they rarely bite but will thrash around, defecate, and release musk from their anal glands. This species can also shed its tail to escape, but unfortunately, the tail doesn’t regenerate like some lizard species.
Currently, the Western Ribbon Snake has a healthy population, but that doesn’t mean it doesn’t have threats. Aquatic habitat degradation and loss and pesticides and road chemicals are believed to have serious negative impacts on their numbers.
#3. Plains Garter Snake
- Thamnophis radix
- Adults average 36 inches in length.
- Coloration is gray-green with a distinctive orange stripe down the back and a greenish-yellow stripe down each side.
- Distinct light yellow spots on the very top of the head!
Plains Garter Snakes are almost always found in southwestern Wisconsin in prairies and grasslands near freshwater sources. They have a fairly large population and adapt well to human-modified landscapes, and you may spot them near abandoned buildings, trash heaps, or vacant lots.
This species is considered to be one of the most cold-tolerant of all snakes! In fact, they will even come out of hibernation on warmer winter days.
The Plains Garter Snake feeds primarily on earthworms, slugs, and small amphibians. However, they have also been observed preying on small mammals and birds, including the Eastern Meadowlark and Bank Swallow.
#4. Chicago Garter Snake
- Thamnophis sirtalis semifasciatus
- Adults reach up to 39 inches in length.
- Coloration is dark brown or black with yellowish stripes down their back and sides.
- The stripes on their sides break into dashed lines near the head.
- The Chicago Garter Snake is a subspecies of the Common Garter Snake.
You’re most likely to find the Chicago Garter Snake in forest and edge habitats. But interestingly, they are only found in the region that surrounds the city of Chicago!
They prefer areas near freshwater sources and can be spotted basking in open areas. These garter snakes are especially cold-tolerant and may even leave hibernation to bask on warm winter days.
Chicago Garter Snakes are similar in behavior and appearance to Eastern Garter Snakes, and both are subspecies of the Common Garter Snake. The main difference is in their appearance. The yellow side stripes on Chicago Garter Snakes are broken into dashed lines near the head.
#5. Butler’s Garter Snake
- Thamnophis butleri
- Adults are slender and range from 15 to 20 inches in length.
- Coloration ranges from olive-brown to black with three yellow to orange stripes, one down the back and one down each side.
- Two rows of dark spots may be visible between the back and side stripes, and the head is usually small.
Butler’s Garter Snakes look almost identical to Eastern Garter Snakes in Wisconsin.
So how do you tell the difference?
What’s unique to Butler’s Garter Snakes is the placement of their side stripes! Technically speaking, they are centered on the third scale row up from the large, elongated scales on the underside of the body. The side stripes also overlap the adjacent second and fourth scale rows.
But unless you’re a herpetologist or want to inspect a snake closely, this probably means nothing to you. For the rest of us, their head is typically a bit small compared to other garter snakes. In addition, when they are threatened, instead of fleeing, they tend to thrash around in place.
This species is considered endangered in parts of its range. Industrial development of agricultural land has caused significant habitat loss and degradation in their range. If you want to find one, look in moist grassy habitats, typically under cover objects like rocks, logs, boards, and other debris.
Do you need additional help identifying garter snakes?
Try this field guide!
Which of these garter snakes have you seen in Wisconsin?
Leave a comment below!