Snakes have been maligned for literally thousands of years. If we’re talking about the venomous kinds, they deserve it. But of the 28 species of snake found in Iowa, only four are venomous—timber rattlesnakes, eastern massasauga, prairie rattlesnakes, and copperheads.
The other day Bryan saw this fellow in the grass near the shop. It’s a three-foot-long western fox snake (Pantherophis vulpinus), a member of the rat snake family. The western fox snake is one of 28 species of snake found in Iowa. That surprised me. That many kinds of snakes, and all I ever hear about is garter snakes and rattlesnakes. Where are they all hiding?
One explanation is probably the fox snake’s coloring. They come in light brown, yellowish tan or gray. This one is tan with around 43 brown blotches edged in black on its back and smaller blotches on its sides. Its belly is yellowish with smaller spots on it, and its head is reddish. Snakes are shy by nature, and with all that color and patterning going on, they probably disappear into the background pretty easily.
Our fox snake is covered with scales, including its eyes. The scales taper to a point and have a line they call a keel down the center. The scales are made of the same stuff that fingernails are made of, and they both protect the snake’s skin and help it move. I remember handling a snake in my sixth-grade science class and thinking it was as cool and smooth as an innertube. The scales all lie in one direction, so I didn’t notice them when I stroked it. I was surprised how heavy it was.
Western fox snakes like to live in moist places like prairies, woods and fields. They also like rocky outcroppings near water. They are named for two animals, rats and foxes, but they don’t look anything like either one. They’re in the rat snake family because they and their cousins eat rats, mice, and other small rodents. And this particular species is called fox snakes because if you handle them, they emit an unpleasant foxy odor. They’re western fox snakes because there’s also an eastern cousin out there. We have routinely called them bull snakes, but bull snakes are bigger, heavier, and differently marked. Both kinds help keep the rodent population down.
The body plan of our fox snake is simple—a triangular head, a long tubular body and a tail. Its head sports a pair of yellow eyes covered with transparent scales. The snake doesn’t have any eyelids, so it can’t blink or close its eyes.
The fox snake does not have any external ears, although it does have an inner ear for balance. It has a nose that it breathes and smells with, and an olfactory bulb to process smells similar to a dog or a human. It also has a forked tongue which it uses to “taste” its environment. By sticking its tongue out and waving it around, or holding it still, it gathers chemical information from its environment. Then it submits what it gathered to a special organ in the roof of its mouth that super-analyzes it to determine where a mouse is, who has passed lately, where a potential mate or threat is, and much more. With two separate organs for processing chemical information in its environment, and a third of its brain dedicated to interpreting what it finds, a snake senses the world very differently than we do.
Fox snakes are constrictors, so they will grab a rat with their mouth and then wrap their strong, sinuous body around it, crushing the rat until its heart stops.
The snake’s mouth is specially adapted to swallow its prey whole. To make this possible, the snake’s upper and lower jaws are divided in two and held together with ligaments. It can move each half of each jaw independently, and uses this trick to open its mouth really wide and to work its prey into its throat and down to its stomach. It uses its backward-curving teeth to keep its prey from sliding out.
Once the rat or mouse moves into the snake’s stomach, it is digested over a few days, and its bones are dissolved. A snake’s digestive juices are a lot stronger than ours.
Snakes are vertebrates, and like all vertebrates, they have a backbone running from head to tail. Ribs are attached at each vertebra forming their skeleton. Muscles all along the ribs allow the snake to move.
Snakes have four distinct types of movement. The most common for our fox snake is the serpentine movement. the snake forms itself into repeating S curves and uses its belly scales to anchor and push itself forward. Fox snakes are good climbers. To climb, they use a concertina movement. They reach up as far as they can, and then bunch their body up like an accordion. They anchor against the tree with their scales and tail, and then stretch out, pushing themselves upward, to re-anchor and do it again. Snakes can also move in a straight line, especially when they’re going down a gopher hole. Sidewinding is the fourth, and most difficult to describe, means of locomotion for certain snakes. Sidewinding is particularly adapted for moving across sand and is associated with desert snakes. Our fox snake primarily moves using the serpentine and concertina methods.
With four distinct types of movement, snakes can travel amazingly fast. They can climb trees, swim, move across sand, dive down a hole, and wrap themselves around my science teacher’s arm.
Snakes don’t regulate their body temperatures the way birds and mammals do. Instead, they warm themselves up by basking in the sun or under the right rocks. Unfortunately, they like to bask on road surfaces where the sun has warmed them, so they get run over. Where a bird may need to eat its body weight every day to provide the fuel it needs to maintain its body temperature, a snake doesn’t need to eat nearly as much to keep it alive.
Fox snakes are often mistaken for rattlesnakes because when they are frightened or annoyed, they rattle the scales on their tails. They don’t bite, however and are not venomous.
We’ll hope this fox snake eats plenty of mice and rats and helps keep those pesky critters under control.
Photo by author