Stayin’ Alive

On a recent trip to Illinois to find snakes, I reflected on the defences, both physical and behavioural, that these oft-maligned animals have evolved to help them avoid becoming dinner.

Southern Illinois is graced with a variety of glorious serpents. Some species extend northward to Ontario and Headwaters, but the forested hills and cliffs of Shawnee National Forest, nestled near the confluence of the Ohio and Mississippi rivers, provides habitat for several exceptional snakes not found here.

I found lots of cottonmouths – venomous pit-vipers that reach their northern range limit in southern Illinois. These stocky snakes use venom to tranquilize prey and to defend themselves. But like all animals, they are gifted with other attributes that help keep them alive. In the swamps where they live, their dark
colour and intricate patterning allow them to hide in mud and vegetation.

Behaviour also assists their survival. If caught out in the open during the day, cottonmouths coil and startle predators by opening mouths lined with the brilliant white they’re named for. Cottonmouths also vibrate their tails and in dry leaves, mimicking the buzzing of rattlesnakes. And after dark cottonmouths
squeeze into rock clefts, out of the reach of nocturnal hunters.

My prize find on my Illinois trip was a copperhead. Copperheads are gorgeous snakes that, like cottonmouths, also protect themselves with venom. In addition, copperheads blend superbly with fallen leaves. Avert your eyes a moment, and these vipers can be hard to relocate.

Another exciting Illinois serpent is the rough green snake. These lovely sinuous animals spend much of their time climbing shrubs. No surprise then that they are a leafy-green colour. But a special behavioural adaptation also protects them.

Rough green snakes “sway” back and forth as they climb, mimicking the movement of branches in the wind. Like us, snakes want to stay alive, and they’ve evolved a grab bag of ways to do that.