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Friday, October 3, 2014

An Eastern Garter Snake

Last summer while working in the yard I came across a snake under some plastic plant containers that I had stashed under the deck.  I started this post soon after, but set it aside until I could develop it more fully.  I've tried to include information about a variety of characteristics of snakes in general as well as this particular snake.  I've also added some references from the web to supplement these photos to highlight the features that differentiate non-venomous from venomous snakes.  

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It had been many years since I'd seen an Eastern Garter Snake around the house.  This one was a bit aggressive at first until I got hold of her and held her for a few minutes. Then she calmed down and was fairly passive. Right away I noticed that this snake was about ready to shed her skin. Her eyes have clouded over and she cannot see very well.  As soon as she sheds her old skin, her eyes will be bright and shiny again and her vision will get back to normal.



SHEDDING

As snakes grow they shed their old, worn, and damaged skins to make room for their increased body size, but also to rid themselves of parasites, like ticks and mites.  Young snakes may shed several times a year because they are growing more rapidly than mature snakes.  Adult snakes may shed as many as four times a year depending on how successful they have been at finding food.  The snake's tough skin protects its body against injury from things like briers and sharp rocks. Another important function of the skin is giving the snake the ability to grip the ground as it moves, and for some snake species, to climb trees.  The skin also keeps the snake from dehydrating by limiting the loss of water.  Just before a snake is ready to shed its skin it secretes a milky fluid under the old skin to help separate it from the new skin that has formed. This is what gives the snake's eye its bluish white appearance.  A snake's skin is made of a material called keratin, just like the hair and fingernails of humans.  I read on the web that while snakes shed their skin in one piece every month or so, we humans shed around one and a half million skin cells every hour. This means that about every 28 days we grow a completely new skin surface.  Wow!


SCALES

In this view you can see the pattern of scales on of the top of the Garter snake's head.  Snakes are born, or hatched, with an exact number of scales.  As the snake grows, each scale gets larger.  It does not add more scales.  Below this picture is a diagram that lists the names of some of the scales that cover a snake's head.





from: http://www.virginiaherpetologicalsociety.com/identification-keys/id-keys-snakes/snake_id_-_6.htm



This photo shows the pattern of scales along the snake's body.  Notice the light colored ridge along the center of the darker scales and the slightly darker ridge along the ones that make up the three rows of tan scales that form the stripe along the back of this Garter Snake.  This ridge is called a keel.  A snake with keeled scales feels rougher or more textured when held than a snake without keeled scales which feels smooth and is often glossy in appearance. Having keeled scales is an adaptation that helps a snake swim in water. Garter snakes are closely related to many species of water snakes which have strongly keeled scales.  An example of a snake with smooth scales is the Black Rat Snake.

Keeled scales

Black and White picture Keeled Scales


Smooth scales

Black and White picture Smooth Scales

from:  http://www.masnakes.org/snakes/scales.html

GENDER

This snake is well over two feet long, I'd guess closer to 30 inches in length.  According to more information that I gleaned from the internet, males are usually under two feet in length with a much slimmer body.  This lady is pretty thick, perhaps with young.  More evidence that this is a female snake is the distinctive tapering of its tail base shown in the picture below.  Notice how the tail narrows abruptly just past the cloaca or vent (a few inches from my left hand) which is typical of female snakes.  See reference material below photo.



  • "By visual appearances - male snakes have a thicker tail base where the two hemipenes lie. This can be seen, even in juvenile garter snakes, with practice.

Female Garter Snake belly scale pattern - Top three (A, B, and C)

Male Garter Snake belly pattern - Bottom two (D and E)


snakesex

  • A, B & C - Female tail; ventral and lateral views.  The tail base enlargement noticeable in some females (see B) appear to male glands, but note that the tail tapers rapidly.

  • D & E - Male tail; ventral and lateral views.  Tail base is thick, and this thickness extends for some distance beyond the vent."

  • Illustration and description by kind permission of Mr Robert J. Riches, author of 'Breeding Snakes in Captivity', 1976
from: http://www.gartersnake.co.uk/maintenance.htm#Sexing snakes



CHARACTERISTICS OF EASTERN GARTER SNAKES

With the snake stretched out it is easy to see the definite stripe that runs the length of her back.  Eastern Garter Snake's overall color can vary from this brownish one to greenish to even reddish or bluish.  




In this side view you can see a tan stripe that is more vague running along each side. Between these stripes and the stripe along her back is a checker-board pattern of darker scales.  The overall effect gives an impression of the garters that were once worn to hold up one's socks.



The dark markings along the edges of the supra-labial scales (upper lip) helps separate this garter snake from the ribbon snakes which look similar but do not have these marks.


The Eastern Garter Snake is ovoviviparous which means that the female snake gives birth to live babies instead of laying eggs.  About half of our North Carolina snake species are live bearers while the other half are egg layers.  Garter snakes can give birth to just a few babies, but as many as 80 at one time.  Garter snakes eat a wide variety of prey including mice, worms, minnows, toads, insects, and lizards.  Garter snakes are sometimes mistakenly referred to as Garden snakes.


CHARACTERISTICS OF NON-VENOMOUS SNAKES THAT ARE DIFFERENT FROM VENOMOUS SNAKES

EYE PUPILS

In this photo you can barely make out the round pupil behind the cloudy eye scale, called a spectacle or an eye cap, that will soon shed along with the rest of her skin.  All of our North Carolina non-venomous snakes have round pupils.  Our venomous snakes, except for the Eastern Coral Snake, have elliptical pupils (shaped like a cat's pupil).  See the diagram below this photo.





venomous versus nonvenomous snake head
from: http://www.ces.ncsu.edu/gaston/Pests/reptiles/images/snakehd2.gif


VENTRAL OR BELLY SCALES

Below is the Eastern Garter Snake's cloaca or vent.  Notice the number of scales across the belly of the snake (ventral scales).  In front of the vent (to the right) there is a series of single scales that spans the belly.  But behind the vent (to the left) there are two scales in a sort of braided arrangement (sorry, the focus isn't the greatest).  In the United States this indicates that this is a non-venomous snake.  The exception to this rule is the colorful (red, yellow, and black) Eastern Coral Snake which is limited to southern coastal areas and a very secretive reptile.  The other venomous snakes of the US have single scales across the belly almost all the way to the tip of the tail.  See the reference material below the photo.


"This is a test for identifying dead snakes or shed snake skins.  This test actually acts as an accurate marker of the snake being venomous or otherwise.  If the tail plates (plates after the anal plate) on the underside of a snake are single, the snake is most probably venomous.  Likewise, if the tail plates are in double plates, the snake is nonvenomous."

Non-venomous belly scale pattern - Top

Venomous belly scale pattern - Bottom

from :http://www.buzzle.com/articles/snake-identification-by-characteristics.html


Below is a great website showing comparisons between several non-venomous snake species and the venomous Copperhead.


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This was a satisfying encounter for me.  It brought back memories of bringing a garter snake home from junior high school in a zipper type notebook.  Of course, it escaped into my bedroom.  My engineer father cornered it in the room and caught it by the neck using a pair of Craftsman lineman's pliers!  I was actually proud of him for that, because he pretty much feared snakes.  I kept the snake for a few days before releasing it along the banks of the Kanawha River.

Being able to go over these pictures that my wife and I took of this garter snake last summer gave me the opportunity to add to what I already knew about these often misunderstood creatures. She's a beauty, isn't she?



2 comments:

  1. Thank you for sharing this information, it helped to understand the garter snake more, and tell the difference.

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    Replies
    1. Thank you, Valerie, for your comment. I have found that taking photos, and pouring over them later, has given me an increased ability to identify local species and to learn more about their lives. It has been a goal of mine in my later years to encourage friends and acquaintances to move from fearing snakes to respecting them. There is so much unfounded fear in peoples' lives. I'd love to be able to help reduce that just a little for a few.
      Have a great day!
      aubrey wiggins

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