Yard Garters

A few weeks after we moved into our home in June of 2000, there was a tremendous rainstorm that flooded the streets and left standing water everywhere. Walking out the side door afterwards, I came across a rain-soaked American Toad (Bufo americanus) crouching by the gate, and then nearly stepped on a Plains Garter Snake (Thamnophis radix). The snake zipped away, and I tucked the toad under a bush, out of harm’s way. In our twenty five years here, I’ve not seen another toad, but the yard garters have been constant companions during fair and foul weather, and a source of much enjoyment.

As a field herper living in the middle of The Great Corn Desert that is central Illinois, and having to drive several hours in any direction to find interesting herps, the novelty of having snakes in my own back yard has not worn off. I’ve come to care a great deal for these urban serpents; I monitor their coming and going, and I’ve made our property more snake friendly. My wife and children learned to look down before stepping outside; the snakes are part of our extended family, and no harm shall come to them while we live here. Even the mailman is on board.

It’s no surprise find snakes where we live. Our house is a century old, and the neighborhood is well-established, starting out as an edge-of-town suburb until after the Second World War, but well within the expanding city now. Property lines are mostly fenced, and there are many mature trees. Back yards are often well-shaded and supplied with features that attract and shelter snakes, including privet hedges, gardens, brick piles, stacks of boards behind garages, and so forth – perfect for secretive eaters of slugs and worms like T. radix.

It wasn’t long before my mind was set on making our property even more radix-friendly. I set up a compost pile on the north side of the garage, where it is mostly shady and cool, lining the sides with concrete block and topping the block with old bricks. This created numerous nooks and crannies for snakes, and nothing attracts slugs, snails and worms like cool and damp block and brick, providing a food supply to go with shelter. Elsewhere in the yard and along the house I strategically placed flagstones in open spaces to provide cover, and for a while I had a board pile on the side of the garage which was used by quite a few snakes.

Over the years I’ve had plenty of opportunities to observe the garters as they went about their business, and I’ve done so in a semi-casual, anecdotal manner. When I saw a snake, I would freeze, and observe its behavior while taking a voucher photo. Most observed behaviors centered around a snake in motion, swishing through the grass or garden, or nosing along the brick foundation of the house.

Sometimes I saw them coiled quietly under vegetation, or basking in the spring sun. Here and there I witnessed courtship and copulation. I saw enough garters enough times that I began to identify unique individuals, based on variations in color or pattern, or scars, or the occasional stubby tail. I’m sure there’s a continuous transient flow of snakes from one yard to another, but when I would see a snake in early spring that I knew from the previous year, it made me feel like I was providing a good place for T. radix to live.

Of course my neighbors also have garter snakes in their yards, and occasionally I see flattened snakes in the streets around my neighborhood. Scaling up from just what I can observe in my yard, there must be thousands of Plains Garter Snakes here in town, sharing living space with mostly unsuspecting humans. I find that an awesome scenario to contemplate. There’s also a nice population on the U of I campus along Boneyard Creek, not very far from my old office, and a couple others near playground parks across town. City living clearly suits these snakes.

I also find Brown Snakes (Storeria dekayi) in my yard, but not often. I’m surprised I don’t see more of these small semi-fossorial serpents, since they share the same basic habitat requirements and prey items as the yard garters. Perhaps they have strong competition from the garter snakes. I’d like to see more Storeria, a snake I’ve loved for more than fifty years.

I observed Plains Garter Snakes on all four sides of the house, and after a while I figured out that I was seeing some of the same snakes on the same side again and again. They all have their little territories, apparently. It took a few years, but eventually I saw active garters in all twelve months of the year. During the winter, a few consecutive warm and sunny days would bring the snakes out to bask. Garter snakes were scarce during July and August, but I would still see a few here and there, especially after rain.

The prime months for observing my yard garters are March, April, and May, with the sweet spot being mid-April through mid-May. It is the Goldilocks zone for Thamnophis radix – a stable range of temperatures that were neither too hot or too cold, and with plenty of rain for drinking, and to bring out the earthworms and slugs that made up the bulk of their diet. During these months I saw multiple snakes each day, and I could walk out in the back yard at random and reliably see at least one. Those are also prime months for mowing the lawn, and after one tragic accident, I learned to walk the path of the mower first, just to scare any snakes out of the way.

The yard garters that lived around the front of the house liked to bask on the steps and on the porch, which faces south. This was a bit of a problem at first for Walter, our regular mailman. He wasn’t really frightened of the snakes, he said, but they did startle him a bit when his mind was on his postal duties. I told Walter what kind of snakes they were, and that they were harmless, and he seems to have adjusted to the situation. Walter is getting ready to retire this year, and I happened to overhear him explaining the ‘snake house’ to another carrier who was training on his route. Thank you, Walter.

The basking snakes usually hang out on the sunward end of the steps, reducing chances of getting stepped on by postal workers or package delivery people. On several occasions I have watched UPS and Amazon drivers walk up the steps and back down again, never seeing the garter snake just a few feet away. More amazing to me than the tunnel vision of the delivery people was that often the snakes wouldn’t move or react to the brief encounter.

By mid-summer I would begin noticing gravid females, and in early September I would start finding newborn garters, usually under cover. Some of these tiny snakes managed to work their way inside the house, and nearly every fall or winter I would encounter one or two in the basement. If it was warm enough, I would release them outside, but twice I had to keep the little ones inside through the winter months. Out in the yard, juveniles seemed to be a prime target for keen-eyed Common Grackles. On three different occasions I observed these birds drop to the ground in the yard, grab a little snake with their beak, and then fly off. The dispassionate and logical part of my mind knows that many offspring of all organisms are part of the overall food web, but that did not keep me from being angry and aggravated at those damned grackles.

For many years, I could confidently identify around a dozen unique snakes each year, and some I would see for three or four years in a row, but things began to change around 2018-2019. I started having fewer snake encounters, and saw fewer snakes that I could identify as unique. My best guess is that local climate change has something to do with it, as there were a number of consecutive spring seasons that were unusually hot and dry, including one with 90-plus degree days in March. I can’t say if these weather events killed snakes outright, but I’m fairly certain that the food supply was impacted. Earthworms seemed scarcer, and the once-plentiful slugs all but disappeared. Another probable factor is the emerald ash borer infestation. In the past three years, the ash tree over my compost pile and two in the neighbor’s yard had to be removed, opening up my back yard to more sun and less shade.

But the yard garters are still hanging on in reduced numbers. I saw only one neonate in 2024, and so far in 2025, I can only identify four unique snakes. But one is a large female who inhabits the back yard, and visibly gravid at the time I write this, so I do have some optimism that the pendulum may swing back the other way, The past few springs have seen more normal temperatures and amounts of precipitation, and for the first time in five years I’ve seen a few slugs this spring in the compost heap and elsewhere. I also have about a third of the back yard converted to a native perennial flower garden now, which provides more shade, cover, and prey items, so I’m keeping my fingers crossed.

City snakes may have an abundance of appropriate habitat and prey items, but they also have to run the gauntlet of outside cats, cars, and lawnmowers. I like to think I’m doing my part to make life a little easier for the local Thamnophis radix.

Thanks for reading this.