Snake Tracks

We’ve reached that time of year when my weekly posts switch from plants and fungi to wildlife tracks and sign. Here’s a nice reminder that not all tracks are made by feet!

The dry summer weather made for great tracking conditions along PEI’s unpaved roads. This site near Mount Stewart had all sorts of footprints from insects, birds, and mammals, along with the unmistakable undulating trail of a snake.

The size of the snake track told me which of our three species was the culprit, and a few minutes of following the trail led me right to it: a Maritime Garter Snake (Thamnophis sirtalis sirtalis).

We rarely think of legless creatures as having different gaits, but they do. In common terms, snake movements get grouped together under the heading of ‘slither’, but these animals actually have four main gaits: serpentine, concertina, rectilinear, and sidewinding. It’s serpentine that we see here.

Serpentine locomotion – also called ‘lateral undulations’ – is the most common way our Garter Snakes get around. As you can see in the video, waves of motion travel from head to tail down the snake’s body as it moves forward.

Each time one of those waves contacts something along the path – a small stone, stick, or ridge of clay in this case – the snake pushes sideways against it. Snakes’ belly scales provide a lot of resistance (friction) against moving sideways or backwards, but little resistance to moving forward. As a result, when a snake pushes sideways against an object its body slides along the path of least resistance and moves forward.

Example of serpentine locomotion - aka lateral undulations - from a Garter Snake on PEI.

Confused? Think of it like ice skating, where the skater pushes sideways to move forward. That works because skate blades provide lots of resistance to moving sideways but very little against moving forward. This snake is just skating gracefully over clay rather than ice!

By now, PEI’s Garter Snakes are tucked in under rocks and logs, in small mammal burrows, or in our sheds and outbuildings for winter hibernation (called ‘brumation’ in reptiles). You won’t find snake tracks in the snow but look for their graceful movements as soon as spring returns to PEI Untamed!