Nature Notes: Garter Snake
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by Ed Robinson
You’d think that I would know better, since it has happened at least 20 times in the last few years. The day is sunny and warm, and I am following my lawn mower along a certain section of stone wall. Yet, once again I am startled as our favorite garter snake slithers from his favorite rock back into the wall. At about 20 inches long, the snake is neither cuddly nor cute, but I’m always glad that he is on duty around our yard. The snake is happy to have a sunny place to rest and warm its cold-blooded system.
Despite population declines due to predation, pollution and the pet market, garter snakes are one of the most common reptiles around us. They can be found from the northern plains of Canada, all the way down through the US and Mexico. The Commonwealth of Massachusetts even passed legislation naming garter snakes the state reptile. Their coloration can vary through a range of browns, tans, and greens, depending upon genetics, geography and diet. You will find these adaptable creatures in a wide variety of habitats from forests to fields, prairies to lawns, generally close to water features.
Garter snakes are opportunistic carnivores, taking a wide range of creatures that can be subdued and eaten whole. While snakes are known to swallow eggs, live animals make up the bulk of their diet. Targets range from frogs, toads, and minnows to small lizards, snakes, and leeches. Insects such as crickets and grasshoppers will serve just fine, as will small rodents when available. The garter snake will grab food with its mouth, and coil its body around its prey to establish control and allow time for the slow process of swallowing.
Garter snakes also serve as prey for raptors, crows, raccoons, fox, fish, turtles, rodents and larger snakes. When threatened, the snake’s first instinct is to flee, but it may coil, shake its tail and strike with its mouth. They also produce a musky secretion with an unpleasant odor, discharged from the cloaca (a single opening on the stomach that serves intestinal, urinary and reproductive tracts). Garter snakes have no fangs, but have small teeth capable of holding prey, and moving that prey into the digestive tract. Although garter snakes are considered non-venomous, they are known to produce a mild neurotoxin in the Duvernoy’s gland at the back of their mouth. This toxin is thought to stun small creatures, and may also aid in the digestive process.
In the autumn, garter snakes stop eating for a couple weeks to clear their digestive tracts of food in a process called brumation. They then travel long distances to large, communal dens used for hibernation. These “hibernacula” may contain hundreds or thousands of snakes. I can remember a childhood friend wading into one site to catch handfuls of snakes, with the unhappy snakes wrapped around his legs and arms (Chris was a bit odd!).
As winter loosens its grip, male snakes emerge from the den and await the females. Once the males smell a female, they wrap her in a mating ball that may contain 25 males, fighting to copulate multiple times. After these orgies, the females crawl off to find food and a den where she can await the birth of her young. Gestation runs from two to three months, with as many as 80-90 tiny snakes born live. The young are independent from birth, and must be very lucky to survive to adulthood to repeat the cycle of life.