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Common Gartersnake

Common Gartersnakes Brumating

1-28-19 gartersnake img_4888Somewhere between two and four feet (depending on where you live in New England) beneath our feet there is a “frost line” below which the ground water in soil doesn’t freeze. Snakes, being reptiles, are ectotherms, and their bodies assume the temperature of the air around them. In order to avoid being frozen to death in the winter, they retreat below the frost line, where they enter a state called brumation – the cold-blooded term for a state of torpor and inactivity that is not true hibernation, but in which a dramatic slowing down of bodily functions occurs. Crevices in south-facing rocky ledges and abandoned woodchuck, fox and skunk dens (and human cellars) often serve as hibernacula, or winter shelters. Common Gartersnakes are known to gather in large numbers (one Canadian den served as a hibernaculum for 8,000 gartersnakes), in order to concentrate the small amount of heat their bodies produce in the winter.

As the air temperature lowers in the fall, a snake’s body temperature falls and its metabolism decreases dramatically. Gartersnakes actively prepare for this by not eating for several weeks prior to hibernating. This allows all of the food they previously consumed to be completely broken down and absorbed into their system. To enhance this process, gartersnakes bask in the sun both before and during their early days of sheltering in hibernacula, warming themselves so as to increase the rate of their metabolism just prior to hibernating.

Should a snake happen to eat a large grasshopper, earthworm or small frog just prior to entering brumation, the snake may become extremely lethargic due to the slowing down of its metabolism, and the contents of its stomach may not be digested as quickly. The longer it takes to process food in its stomach, the greater the chances that this dead material will start to decay, which could result in serious illness to the snake.

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Young Common Gartersnakes Appearing

8-3-18 garter snake 081Seventy percent of the world’s snakes lay eggs (oviparous). The rest give birth to live young (viviparous). Oviparous snakes tend to live in warmer climates, where the substrate they lay their eggs in is warm enough to incubate the eggs.  (Most egg-laying snakes deposit their eggs and then depart, relying on the substrate to incubate the eggs.)  Viviparous snakes tend to live in cooler regions, where the ground is too cold to provide incubation.

There is a distinction between egg-laying snakes.  The majority of snakes that lay eggs do so outside their body, in a protected area such as a rotting log.  These snakes are known as oviparous. There are also egg-laying snakes that retain their eggs inside their bodies until they’re ready to hatch. These snakes are called ovoviviparous. Ovoviviparous snakes, such as the Common Gartersnake, appear to give birth to live young, but they actually don’t. Unlike viviparous species, there is no placental connection, or transfer of fluids, between mothers and babies, because the developing young snakes feed on the substances contained in their individual eggs. The snakes emerge from the mother when they hatch from their eggs, giving them the appearance of “live” births. The gestation period for oviparous snakes is generally longer than those of ovoviviparous snakes and vary from a few weeks to a few months in length. (Photo: very young Common Gartersnake, Thamnophis sirtalis sirtalis, consuming an earthworm)

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Common Gartersnakes Mating

4-30-15  common gartersnake IMG_9163Common Gartersnakes begin mating in the spring as soon as they emerge from brumation (a reptilian state of dormancy similar to hibernation in mammals, but involving different metabolic processes). The males leave the den first and wait for the females to exit. Once the females leave the den the males surround them, forming what is called a mating ball (one female and many males). The males give off pheromones that attract the female. After the female has chosen her mate and mated, she leaves. while the males stay to re-mate with other available females. The females have the ability to store the male’s sperm until it is needed and thus a female may not mate if she does not find a proper partner.

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Common Gartersnakes Giving Birth

8-15-14  common gartersnake 082Common Gartersnakes mate soon after emerging from hibernation in the spring, in March or April, and four months later the females give birth to live young. The newborn snakes are 5 to 9 inches long at birth and from day one have to fend for themselves. Their diet at this early stage consists of earthworms, insects, slugs, tadpoles, small frogs and fish. If there is an abundant supply of food, the young snakes can grow as much as 1 ½ inches a month during their first year. Earthworms are their preferred diet and gartersnakes are known for their ability to find them, even underground. It turns out that earthworms produce a chemical substance in their skin that is easily detected by (and attractive to) Common Gartersnakes. (Thanks to Eli Holland, who located the worm-eating newborn Common Gartersnake in the photograph.)

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