Snake
identification sometimes requires close examination of obscure details.
For example, there are several look-alike garter snake species, plus ribbon snakes look a
lot like garter snakes. Therefore, if we want to be sure we really have the Common Garter
Snake, Thamnophis sirtalis, we need to make decisions on such obscure
characteristics as those referred to below. Here are the Common Garter Snake's main field
marks:
On the Common
Garter Snake, each side stripe is confined to the 2nd and 3rd scale rows (except in
Texas). (This shows that in snakes the scales don't grow
randomly, like hairs on a human body; they occur in rows,
and each row is numbered. At the right you see the shed skin of a Racer, Coluber
constrictor clearly showing each individual scale. )
- Between the stripes there are often red blotches or a double row of
alternating black spots.
- Common Garter Snakes have 7 upper lip-scales. (This
shows that in critical places, especially on the head, even individual scales may be
numbered! Note the distinct scales in the Racer's head in the photo.)
- Common Garter Snakes have 19 rows of scales. (The
Racer in the photo has 17 rows.)
MORE ABOUT
COMMON GARTER SNAKES
Common Garter Snakes are small
snakes, usually only a couple of feet long, but capable of being much longer. Long stripes
extend from head to tail, so they don't look at all like any venomous species in North
America. Though they are peaceful creatures content to eat frogs, toads, earthworms, mice
and, if they can, fish, if you mishandle them they'll bite your hand. If you manage to
hold one's head so it can't bite, it wraps its body around your arm, smearing you with a
very disagreeably smelling musk. |
- Garter snake have keeled scales, which means that
each individual scale has a narrow ridge running down its middle. (This is an important
feature when identifying groups of snakes. Garter snakes and water snakes have
keeled scales, rat snakes have weakly keeled scales, and king snakes and racers have
"smooth" scales.)
- Garter snake anal plates -- the large scale or
scales next to the anus, at the end of the broad belly plates -- are single. (Anal
plates are also important when identifying groups of snakes. Garter snakes, king
snakes, and pit vipers, for instance, have single anal plates, but in the water snakes,
racers, and rat snakes, the plates are divided.)
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