New Garter Snake in the Ozarks

Sometime back I was complaining in a past blog about the name change of the black rat snake to the Texas rat snake.  I just discovered that the Texans are invading our border again.

Snake in the bush- Valley Water Mill trail

On the Master Naturalist plant survey at Valley Water Mill, I was trailing along with Linda Ellis and the rest of the botanical crew,* telling them that I would be looking for snakes.  While I was scanning the ground, Linda found this beauty on the branches of an invasive honeysuckle two feet off the ground.  It is a garter snake and her first impression was it might be a red-sided garter snake.

When we got back home I started to look it up.  There are 5 sub-species of garter snakes in Missouri according to the books, with 3 found on the prairies.  We would expect to find the Eastern garter snake, Thamnophis sirtalis sirtalis, across southern Missouri and the red-sided species Thamnophis sirtalis parietalis in the southwest part of the state. Looking at the pictures I couldn't make an ID.  Like most things, it is a little more complicated than just the color.

Eastern garter snake- Herpnet.net

I sent the picture to my snake master, Brian Edmond who came up with an unexpected answer.  These two species have enough color variation that you can't ID them by color.  Even Amphibians and Reptiles of Missouri lumps them together.  Its key goes into the details of counting scales, details that only a dedicated herpetologist could love.

But it is even more complicated.  Our snake is a Texas garter snake.  While the books say it doesn't live here, Brian's research paper cited below** reports that it is found in the White River Hills ecoregion and is a common "town snake" in Springfield, Missouri!

Although I complain about the name changes and all the Latin, this is more than just recognizing who first saw the species.  With more people looking at nature and reporting it, we are rewriting the books on many species.  The small differences in sub-species frequently means studying details that I wouldn't notice.  As I have proven so often on this blog when trying to identify a species of anything, it isn't just what you know but who you know.

Brian sent me some additional comments worth repeating here.

"The concept of subspecies is problematic for many species, including Thamnophis sirtalis. While there are definite regional patterns if you go far enough--this species is apparently always a good "red-sided" in Kansas--they seem to be a confusing mess in Missouri. Johnson shows an "intergradation zone" between the two subspecies across much of the state, but I've seen animals well outside of this zone that exhibit the patterns of the other "subspecies".  Like other wide-ranging species, I believe Thamnophis sirtalis is due for a DNA study, with the result being a splitting off of several new species. I wouldn't be surprised to find that we have 2 or 3 (or more!) new garter snakes in Missouri." 

*   Debbie Lewis, Mary McCarthy,  David Ketchum, Barb and I.
** Brian's paper with interesting details is at mha.moherp.org page 25-26.