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Garter snake

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Garter snake
Western terrestrial garter snake juvie.jpg
Scientific Classification
Species
Thamnophis range.png
Thamnophis is the most widely distributed genus of snakes in North America

Garter snakes, also known as garden snakes, are the most common reptile genus of terrestrial snakes in North America, spanning from Alaska to Central America. Depending on geographic location, these medium-sized snakes may eat earthworms, frogs, small fish, or newts. Garter snakes prefer semi-aquatic environments and utilize their aqueous environment as they flee from predators. Garter snakes generally hibernate during the winter months.

Body Design

Using its tongue, this garter snake scours the area for food with the help of its Jacobson's organs.

Garter snakes are small to medium sized reptiles ranging in length from 8 inches[3] to 64 inches.[4] These snakes feature a long slender body with small scales covering its dorsal and side surfaces. On its ventral surface, wider scales known as scutes aid in locomotion by gripping the ground or climbing surface. Scales of various sizes also coat the snake's head, which can be used to identify them by species.[3] These scales, which are composed of keratin, collectively refer to the snake's skin.[5] A snake utilzes its scales for protection from predators, locomotion, and to retain moisture.[6] Garter snakes display a wide range of colors and markings on their bodies with colors such as brown, blue, bright red, pale green, yellow, black, orange, and several other variations. Some may have spots, stripes, diamonds, checkers or any combination of these. The skeletal structure of a garter snake possesses a skull followed by two un-ribbed "atlas" vertebrae and 1-3 un-ribbed neck vertebrae. Depending on the length of the snake, several ribbed vertebrae span the length of the reptile, ending with 2-10 tail vertebrae.[3] Within this endothermic reptile's internal body cavity, a three-chambered heart pumps blood in a closed circulatory system throughout the body, obtaining oxygenated blood from a single functionaing lung. Garter snakes breathe using external nares and a glottis, a small hole behind their tongue that allow air to pass into the lung. These structures are essential as snakes devour food that blocks their throats.[7]

Garter snakes, like all snakes, possess a lower jaw that is not structurally connected to their upper jaws, allowing large whole meals to pass into their stomachs.[3] Most garter snakes possess small inward facing teeth used to hold securely to prey.[8] After devouring prey, the meal will slowly pass through the snake's digestive system, which treats the meal with enzymes until broken down. Undigestible waste passes out of the snake's cloaca, which is divided into the opradaeum for solid waste and urodaeum for urine.[9] Garter snakes also have a very accute sense of sight and smell. Two eyes, responsible for vision, and located on each side of the head. Jacobson's organs, located on the roof of their mouths, are used to detect specific chemicals in the air as the tongue transfers these stimuli to the organs.[10] In general, male garters are generally smaller in size than the females and are characterized by a foul odor excreted from the cloaca during stress.[11] In terms of reproductive organs, the male snakes possesses a pair of testes and a unique hemipenes that must be turned inside out to be inserted into the female's cloaca. The specific cloaca structure between garter snake species often differs, ensuring that only males of the same species can mate with the female.[10]

Life Cycle

During early spring, male garter snakes will frenetically attempt to mate with a female, who attracts many males with pheremones.

Most garter snakes live in moist areas near a water source.[12] During early spring, garter snakes will leave their winter dens, shared by several garter snakes, to mate with females, who emerge slightly later. When a female is identified by her pheremones, all of the present males will quickly slither around and wrap themselves around the female in a breeding frenzy of up to 20 or more snakes. This is due to the lower population of female garter snakes than males of the same species.[13] The female soon becomes pregnant and will remain in gestation for 2-3 months. Unlike most snakes, garter snakes are ovoviviparous and give live birth in litters of 2-40, depending on species.[14]

After birth in late spring, these infant garter snakes will set out independently in search of food, continuing to eat and grow througout the summer months. A young garter snake may shed its skin once every 4-5 weeks while an older snake may only shed a few times a year.[3] As fall aproaches, these garters will consume less food, preparing for brumation during the winter months, where low temperatures and little prey force garter snake to enter this state of "hibernation". Many snakes of the same species will "hibernate" together in nearly any protected hole they can find, from rodent burrows and old farm wells to rock fissures and anthills. This is period of decreased activity and metabolic rate, and these snakes will reawaken in early spring to mate and begin the cycle over again.[13] Most wild garter snakes will become the victim of predators within the first two years. However, rare cases have seen garter snakes live for around six years. In captivity, these snakes have been observed to live up to 15 years![15]

Ecology

Using specialized jaws, garter snakes can swallow prey much larger in diameter than itself.

Similar to most species in genus Thamnophis, the common garter snake possesses a wide range from southeast Alaska, Canada, mainland United States, and Mexico.[16] In fact, garter snakes are found in more northern locations than any other classification of snakes. Most garter snakes are semi-aquatic and prefer to hibernate and hunt near water.[17] Depending on availability of prey and geographic location, garter snakes possess a very wide diet range and are considered generalists. However, most garter snakes prefer small fish, earthworms, frogs, and other small amphibians. These reptiles are one of the few known animals with tolerance to defensive toxins contained within certain toads and newts.[17] Although universally considered non-venomous themselves, garter snakes do possess a pair of small glands where toxins may be secreted during prolonged bites on prey.[18] However, lacking fangs, garter snakes are unable to envenomate humans or larger animals.[19] Garter snakes are most often preyed upon by large fish, bullfrogs, snapping turtles, milk snakes, crows, hawks, great blue herons, raccoons, foxes, squirrels, and shrews. These snakes utilize their skin coloration as camouflage and quick agility to escape from predators. If unable to flee or dart into the water, they may coil themselves. This gives the appearance of a larger body and also prepares their stance fro a strike if necessary. If all else fails, these snakes may secrete a foul odor from the cloaca or urinate on their attacker.

Garter snakes, soon after birth, generally live independently and congregate only to breed or hibernate during the winter months, although some species may sleep together each night to prevent heat loss. These snakes are diurnal and will bask in the sun for many hours a day. They “communicate” primarily through pheremones, chemical secretions used to identify snakes by species or call snakes to breed. Garters contribute to their environments by controlling the populations of insect pests. They are also hosts for a parasitic roundworm that lives in the posterior tissues of the snake's body.[15] Humans, too, have incorporated garter snakes into their way of life, including some native American tribes, who considered it a symbol of jealousy or dishonesty.[20]

Pets

Many species of garter snake are kept as pets for their beautiful coloration and lack of toxic venom.

Due to their mild temperament, lack of potent venom, and often vibrant colors, many individuals keep garter snakes as pets. While some may catch wild garter snakes to keep, many experts point to the fact that wild caught snakes are much more subject to stress, making them much more difficult to maintain.[17] Stress in snakes has been linked to unusual cycles of shedding, lethargic behavior, less food intake, and a dulling of colors. Due to these factors, experts advise purchasing garter snakes raised in captivity.[21] Garter snakes are generally regarded as being easy to care for, as mice or earthworms will sufficiently comprise its diet, and excessive heat is not necessary.[22]

Although garter snakes are known to occasionally bite in self-defense, their small teeth and harmless venom make for a relatively painless bite to its keeper.[19] Additionally, garter snake cages do not need to be too large, as huge terrestrial habitats will stress the snake from vulnerability and insecurity.[23] Garter snakes can be purchased at relatively low prices due to commonality. In general, garter snakes have become popular pets due to their ease in care and intriguing characteristics.[18]


Video

This garter snake, Thamnophis sirtalis, stalks a frog in a semi-aquatic environment.

Gallery

References

  1. Thamnophis sirtalis sirtalis WikiSpecies. Web. Updated 25 February 2011.
  2. Crowe, Jonathan. Snake Species Guide Gartersnake.info. Web. Accessed 19 April 2014.
  3. 3.0 3.1 3.2 3.3 3.4 Cates, Jerry. Snake Anatomy & Physiology Bugs In The News. Web. Updated 23 October 2013.
  4. [http://www.biologicaldiversity.org/species/reptiles/giant_garter_snake/ SAVING THE GIANT GARTER SNAKE ] Center For Biological Diversity. Web. Accessed 23 March 2014.
  5. MacRae, Maria. Common Garter Snake Canadian Wildlife Federation. Web. Accessed 23 March 2014.
  6. Snake Skin Natural Standard. Web. Published 2013.
  7. Mader, Douglas. Snake Respiratory System Anatomy Reptiles. Web. Accessed 23 March 2014.
  8. Crowe, Jonathan. Handling Garter Snake.info. Web. Updated 1 June 2012.
  9. Digestive System of Snakes Snakes. Web. Accessed 23 March 2014.
  10. 10.0 10.1 Snake Structure Snakes. Web. Accessed 23 March 2014.
  11. Common Garter Snake Snakes of Massachusetts. Web. Accessed 23 March 2014.
  12. Hibernation, diet, habitats, dimorphism and mating Garter Snake. Web. Accessed 23 March 2014.
  13. 13.0 13.1 Pistorius, Alan. The Garter Snake Northern Woodlands. Web. Updated 18 August 2002.
  14. Common Garter Snake Chattanooga Arboretum and Nature Center. Web. Accessed 23 March 2014.
  15. 15.0 15.1 Zimmerman, R. Common Garter Snake Kids' Inquiry of Diverse Species. Web. Accessed 23 March 2014.
  16. common garter snake ARKive. Web. Accessed 6 April 2014.
  17. 17.0 17.1 17.2 Hibernation GarterSnake. Web. Accessed 6 April 2014.
  18. 18.0 18.1 Kruzer, Adrienne. Pet Garter Snakes About.com. Web. Accessed 6 April 2014.
  19. 19.0 19.1 Anzelone, Marielle. NoNeedToFear TheNewYorkTimes. Web. Published 5 June 2012.
  20. GarterSnakeMythology Native Laguages. Web. Accessed 6 April 2014.
  21. Kaplan, Melissa.Signs of Illness and Stress in Reptiles HerpCareCollection. Web. Updated 1 January 2014.
  22. Garter Snake Care Guide Reptiles-n-Critters. Web. Accessed 6 April 2014.
  23. Crowe, Jonathan. Housing GarterSnake.info. Web. Updated 27 June 2014.