I love snakes, and my favorite species is the Common Gartersnake, Thamnophis sirtalis. As the name implies, this species happens to be one of the most common snakes in much of the United States. But although the Common Gartersnake is abundant and widespread, many people don't give these snakes much thought; our thoughts are preoccupied on "cooler" snake species, like Timber Rattlesnakes, or Rough Green Snakes, or Indigo Snakes. We like the flashier and the rarer species, and we oftentimes pay little attention to the common species that we see all the time. However, the Common Gartersnake is an awesome species as well, and in this post I want to shed some light on this commonly-seen, yet commonly-dismissed, snake.
Before we jump in to ecology and the like, let's talk about names. The scientific name of this species is Thamnophis sirtalis. That's easy enough; this name was officially agreed upon by herpetologists. But then we have the common name, and you’ll find several of those. I was originally taught these snakes were "garden snakes," which is a name many people call them by. You might have heard someone call them “gardener snakes” as well.
The real common name, however, is "Gartersnake." The people who originally gave this name to this snake did so due to its patterning, which resembled the stripes on the garters commonly worn by people back then. Since people don't really wear garters nowadays, that resemblance became lost on the general public. For many people, the name morphed into "garden snake" or the like, as this sounded similar to garter, and people would sometimes find these snakes in their garden. The altered name made sense for many people. However, in keeping with the naming tradition, the real common name continues to be the Gartersnake. There are several other species of Gartersnake in the Thamnophis genus, but T. sirtalis is the most common and widespread of those species, and is consequently called the Common Gartersnake. There are also several subspecies of the Common Gartersnake, and the one in Ohio is the Eastern Common Gartersnake, Thamnophis sirtalis sirtalis. When talking about this specific subspecies, most people drop the "Common" from the name and simply call it the Eastern Gartersnake.
There are a couple more things to mention about the Common Gartersnake before jumping into its natural history. First, the Common Gartersnake is a completely harmless, non-venomous snake. Second, there's a myth that the Common Gartersnake will not bite people. That's not necessarily true. If you pick up a Common Gartersnake, there's a good chance it might bite you (especially if it's a female). The good news, however, is that their bite is nothing to worry about. In fact, it doesn't really hurt at all. What's the best way to avoid the bite of any snake? It's simple: keep your distance and leave the snake alone. Snakes don't like confrontation, and they won't do anything to you unless you do something to them first.
As a quick aside, do you know how awesome it is for a reptile lover to have a snake hibernaculum on their campus? It's amazing.
Even more interesting is the fact that the Common Gartersnake gives live birth. Most, but not all, snakes lay eggs, which then hatch out on their own. The female Common Gartersnake, on the other hand, never lays her eggs. The eggs get fertilized by the males, but then stay within the female. These eggs then develop and eventually hatch within the female, who then gives birth to juvenile snakes instead of the eggs like most other snake species. Although this appears similar to how mammals give birth, it is quite different. With mammals, the female actively exchanges oxygen, food, and other substances with the growing fetus. With live-young-bearing snakes, however, the female never exchanges anything with the fetuses. Instead, the eggs in which the fetuses are contained in have all the substances required for development; the female simply carries these eggs inside of her instead of depositing somewhere in a nest or the like.
Like other reptiles, Common Gartersnakes are ectothermic (AKA "cold-blooded," but that isn't really a good term as their blood isn't always "cold," and it can actually be warmer than the temperature of our blood). Ectothermy is where an organism doesn't produce its own body heat through metabolic processes, but instead relies on environmental heat. We humans are, on the other hand, endothermic, meaning we create our own body heat through metabolic processes. When an organism is ectothermic, they are at the mercy of the environment. If it's too cold outside, an ectothermic animal cannot function and may die. If it's too hot, that ectothermic animal also can't function and may die. As a result, ectothermic animals must thermoregulate, meaning they must regulate their body temperature by either moving to a warmer location or moving to a cooler location, depending on their current need. Common Gartersnakes do this by basking in the sun when they want to heat up, or retreating to a shaded area when they want to cool down.
Melanism is a normally occurring, albeit rare, condition (like albinism) within most animals, but we don't see many melanistic animals because being melanistic normally isn't an advantage. However, being melanistic is a big plus for Common Gartersnakes. The color black absorbs all the wavelengths of the white light of the Sun, so a melanistic individual can absorb more heat energy than a normal-colored individual. In fact, one study found that melanistic individuals were able to stay about 2°F warmer than their normal counterparts. In the northern portions of the Gartersnake's range, where the temperatures are much cooler, this ability to remain relatively warmer gives melanistic individuals an advantage; they can be active earlier and for longer periods of time, meaning they can hunt more and end up growing bigger. These melanistic individuals end up doing better than the normal individuals, and the melanism-causing genes end up being passed on to more and more baby snakes. This selective advantage has resulted in up to 50% of the Common Gartersnakes around the Western Basin of Lake Erie being melanistic. The individual pictured in the last two photos, for example, was from this region.
Thanks for reading!