Christopher earned his master's in biology at the University of Northern Colorado in 2013. He studied venomous snakes and their venoms.
Snakes of the Hoosier State
So, you've come across a snake in Indiana and would like to identify it, eh? Well, unfortunately, snake identification is generally a very difficult and complicated affair. It commonly requires you to have much more information than you can possibly collect from a *safe* distance, but you can at least narrow down the list of possible suspects from several feet away. What I present below is the means by which you can discern every one of the 39 snake taxa (species and subspecies) in Indiana. It involves using a dichotomous key to figure out which snake you have before you.
A Word of Caution!
It is very difficult to identify a snake from a "safe" distance! The best thing to do when you come across a snake is to leave it be and respect its space. Do NOT attempt to handle or kill any snake, as this is when a majority of snakebites occur.
What Is a Dichotomous Key?
A dichotomous (or taxonomic) key provides you with a series of questions/choices to answer/make in relation to what you are observing on your snake specimen. It is a way to deduce a snake's variety by eliminating others and narrowing down the "correct" choice.
This key was designed by taking into consideration the most common physical characteristics of Indiana's snakes at adult size (under "standard" conditions: dry/clean with minimal scarring and intact tail). This key won't help much to identify "aberrant" specimens with unusual colors/patterns (e.g., albinos and other "mutants" or natural variants), neonate snakes (as a couple of species exhibit ontogenetic changes in color/pattern), or hybrids (which possess a mixture of characteristics between two different snake taxa).
For aid in identifying "aberrant" specimens, please consult a snake expert or use a high-quality field guide.
How to Use This Guide to Identify Snakes in Indiana
In order to make the best use of this key, you will need (in most cases) to have intimate access to the animal, although a camera with a very good zoom lens can substitute for this. Please keep in mind that the best approach upon encountering any snake in the wild is to appreciate the animal from a distance. If you have access to a shed skin, a dead snake, or a live snake that absolutely had to be captured in order to be relocated and/or identified, then the next section will aid in determining what kind of snake it is.
As all of Indiana's rear-fanged venomous snakes are relatively harmless (with regard to humans; click here to understand why), I will not emphasize which snakes on this list belong to that group, but I will point out which snakes are front-fanged venomous (learn more about front- and rear-fanged snakes, as well as what "venomous" means) because their venoms have the potential to be quite dangerous. Once you have your snake or skin shed readily available for identification, please continue your research to find out more about your snake.
Scale row count is one tool to identify snakes, as is the morphology of the anal plate. This is the scale that covers the cloaca, or the snake's unified excretion orifice, on the underside of the tail. The maximum recorded total body length is also used but will not be discussed in this article.
What Are Keeled Scales and Where Is the Anal Plate?
A snake's scales and whether they are "keeled" or smooth is important information. Keeled scales have a ridge along the dorsal mid-line, like the keel of a boat, giving the snake a "rough" texture. Smooth-scaled snakes do not have these ridges. Another important piece of information when identifying a snake is its approximate distribution range. The habitat ranges for Indiana's snakes are specified in brackets in the key. This key also poses questions about snake specimens to help you narrow down the possibilities. While some answers will yield the identity of your unknown snake, others will simply point you in the right direction.
Dichotomous Key for Identifying Snakes in Indiana
1. Vertical pupils? Yes, go to step two; No, go to step five.
2. Rattle at end of tail? Yes, go to step three; No, go to step four.
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3. Large body size/length with small scales on top of the head and dark markings on the back that may be "chevron-shaped" = Timber Rattlesnake (Crotalus horridus) found in the southern third of Indiana. "Front-fanged Venomous;" Small body size/length with large scales on top of head = Eastern Massasauga Rattlesnake (Sistrurus catenatus catenatus) found in the northern third of Indiana. "Front-fanged Venomous."
4. Bottom of "eye band" extends from middle of eye and curves around to corner of jaw with a copper-colored body = Northern Copperhead (Agkistrodon contortrix mokasen) found in southern Indiana. "Front-fanged Venomous." Bottom of "eye band" runs just below eye and goes straight to corner of jaw with a dark-colored body (may appear blackish) = Western Cottonmouth (Agkistrodon piscivorus leucostoma) found only in Dubois and Harrison counties. "Front-fanged Venomous."
5. Single stripe down middle of back with or without a single row of side stripes? Yes, go to step six; No, go to step 16.
6. Dull-colored (tan/blue/red) back stripe = go to step seven; Bright-colored (orange/yellow/white) back stripe = go to step ten.
7. Three light-colored spots on nape of neck with red-colored belly? Yes = Northern Redbelly Snake (Storeria occipitomaculata occipitomaculata) found everywhere but central two-thirds of Indiana. No, go to step eight.
8. Two parallel rows of small dark spots bordering the back stripe? Yes, go to step nine. No = Western Earth Snake (Virginia valeriae elegans) found in southwestern third of Indiana.
9. Parallel spots fused by numerous narrow crossbands across midline? Yes = Midland Brown Snake (Storeria dekayi wrightorum) found throughout state; No = Northern Brown Snake (Storeria dekayi dekayi) found in northeast corner of Indiana.
10. White/yellow-colored bar in front of eyes with uniformly white/yellow-colored labial (mouth/lip) scales and side stripe occupying third and fourth scale rows? Yes, go to step 11; No, go to step 13.
11. Two fused light-colored spots on crown of head with black (not brown/reddish) stripe (below yellowish side stripe) directly bordering belly scales? Yes = Western Ribbon Snake (Thamnophis proximus proximus) found everywhere but southeast and eastcentral Indiana; No, go to step 12.
12. Dark black/brown back with yellowish back stripe, slightly shorter tail (less than 33.5% of total length in males and less than 32.5% in females), and slightly wider lateral stripes (bleeding over into the second scale row near the neck) = Northern Ribbon Snake (Thamnophis sauritus septentrionalis) found in northern two-thirds of Indiana; Reddish-brown back with orangish back stripe, slightly longer tail (more than 33.5% of total length in males and more than 32.5% in females), and slightly thinner lateral stripes = Eastern Ribbon Snake (Thamnophis sauritus sauritus) found in southwest and southcentral Indiana.
13. Side stripe occupies second and third scale rows? Yes, go to step 14; No, go to step 15.
14. Black vertical bars interrupt side stripes near neck? Yes = Chicago Garter Snake (Thamnophis sirtalis semifasciatus) found only in Porter county; No = Eastern Garter Snake (Thamnophis sirtalis sirtalis) found throughout state.
15. Side stripe occupies second through fourth scale rows with uniformly colored labial (mouth/lip) scales and smallish head = Butler's Garter Snake (Thamnophis butleri) found in northeastern Indiana; Side stripe occupies third and fourth scale rows = Plains Garter Snake (Thamnophis radix) found in northwestern Indiana.
16. Solid dorsal color with or without multiple, faint stripes down back (with no other underlying color/pattern down middle of back, but may have side stripes)? Yes, go to step 17; No, go to step 25.
17. Light-colored collar around neck? Yes, go to step 18; No, go to step 19.
18. Blue/black dorsal color with bright yellow/orange-colored belly = Northern Ringneck Snake (Diadophis punctatus edwardsii) found everywhere but central two-thirds of Indiana; Tan dorsal color with cream-colored belly = Southeastern Crowned Snake (Tantilla coronata) found only in Floyd and Clark counties.
19. Side stripes (whether they are intact or interrupted)? Yes, go to step 20; No, go to step 22.
20. Red side stripes interrupted by large, vertical black bars (that are an extension of the black dorsal color)? Yes = Western Mud Snake (Farancia abacura reinwardtii) used to be found in the southwestern tip of Indiana, but is now considered to be extirpated from the state; No, go to step 21.
21. Pink side stripes are an extension of the ventral color up to the 3rd scale row with solid-colored belly = Midwestern Worm Snake (Carphophis amoenus helenae) found in southern Indiana; White/yellow side stripes on first and second scale rows with striped belly (and sometimes with faint stripes along back) = Queen Snake (Regina septemvittata) found everywhere but the southwestern corner of Indiana.
22. Green dorsal color? Yes, go to step 23; No, go to step 24.
23. Longer tail (37-41.5% of total length in males and 36.5-39% in females) with keeled scales = Northern Rough Green Snake (Opheodrys aestivus aestivus) found in southern third of Indiana; Shorter tail (30.8-35% of total length in males and 27-30.5% in females) with smooth scales = Western Smooth Green Snake (Opheodrys vernalis blanchardi) found in northwestern Indiana.
24. Blue-steel dorsal color becoming blue on the bottom of the sides = Blue Racer (Coluber constrictor foxii) found in northern two-thirds of Indiana; Black dorsal color becoming gray on the bottom of the sides = Southern Black Racer (Coluber constrictor priapus) found in the southern third of Indiana.
25. Vibrant, large, red-colored saddle-shaped blotches on back with black and white borders? Yes, go to step 26; No, go to step 27.
26. Pointed snout with solid-colored, whitish belly = Northern Scarlet Snake (Cemophora coccinea copei) found only in Floyd county; "Normal" snout with dark blotches on belly = Red Milk Snake (Lampropeltis triangulum syspila) found in southwestern Indiana.
27. Upturned nose, like a hog's? Yes = Eastern Hognose Snake (Heterodon platirhinos) found throughout state; No, go to step 28.
28. V or Y-shaped patch on head/neck? Yes, go to step 29; No, go to step 30.
29. Brown blotches on belly and thin, dark blotches (that look like crossbars) on back that are approximately the same width as the light spaces between them = Prairie Kingsnake (Lampropeltis calligaster calligaster) found in southwest/southcentral Indiana, as well as along western state border; Black blotches on belly and thick, dark blotches (that look squarish) on back that are approximately twice the width of the light spaces between them = Eastern Milk Snake (Lampropeltis triangulum triangulum) found everywhere except southwestern Indiana.
30. Red-colored belly bordered by row of black spots with four rows of black spots on back? Yes = Kirtland's Snake (Clonophis kirtlandii) found everywhere except the southwestern corner of Indiana; No, go to step 31.
31. Copper-colored belly/lips without any dark markings on underside of tail? Yes = Copperbelly Water Snake (Nerodia erythrogaster neglecta) found in the southern third and northeast corner of Indiana; No, go to step 32.
32. Predominantly black dorsal color (with minor hint of underlying color/pattern) and weakly keeled or smooth scales? Yes, go to step 33; No, go to step 34. Note: The water snakes, in my opinion, only ever look light/dark gray or brown when dry (which is a stipulation of this key), and possess strongly keeled scales down the middle of their backs.
33. Shorter tail (12-15% of total length in males and 10-12.5% in females) with smooth scales = Black Kingsnake (Lampropeltis nigra) found in southwestern third of Indiana; Longer tail (16-19% of total length in males and 14.5-18% in females) with weakly keeled scales = Black Rat Snake (Pantherophis obsoletus) found throughout the state.
34. Tan-colored body with a dark band between the eyes that extends to the corner of the jaw? Yes, go to step 35; No, go to step 36.
35. Sides covered with single row of moderate-sized dark spots, longer tail (14-18% of total length in males and 12.5-15.7% in females), and weakly keeled scales = Western Fox Snake (Pantherophis ramspotti) found in northwestern corner of Indiana; Sides covered with multiple rows of little dark spots, shorter tail (11-12.5% of total length in males and 10-11% in females), and strongly keeled scales = Bullsnake (Pituophis catenifer sayi) found in northwestern Indiana.
36. Reticulated (net or diamond-like) dorsal pattern and a cream-colored belly with evenly distributed black markings? Yes = Northern Diamondback Water Snake (Nerodia rhombifer rhombifer) found in southwestern corner of Indiana; No, go to step 37.