A Place For Snakes (Fall, 1998)

Try to describe a snake and you come out sounding like a gunslinger hurling insults in a B western: You limbless, slithering, fork-tongued, cold-blooded, scaly-skinned reptile! Perhaps we are both fascinated by and fearful of snakes because they are so different from us. Most obviously, they lack limbs, though a few species such as the rubber boa, which has been reported in western Colorado, have tiny remnant legs called spurs. Snakes have an unblinking stare, which isn't due to a Clint Eastwood-style machismo but to a lack of eyelids. If you've ever found a snakeskin you know that snakes shed their worn outer skin all in one piece. Though a snake's skin is scaly, people are frequently surprised to find many snakes feel smooth, dry, and often warm.

Cover of the fall, 1998 issue of Colorado's Wildlife Company. Calling a snake cold-blooded is, of course, a reference to its thermodynamics rather than its emotions. Snakes are ectothermic, literally "outside heating”, meaning they can't regulate their body temperature internally. Their temperature, and thus their activity, fluctuates with the environmental temperature. Snakes bask in the sun—on rocks, paved roads, and other warm places—to raise their body temperature, moving into the shade when the sun is too strong. In Colorado, snakes are found in the greatest diversity and numbers in warmer, lower elevation habitats, particularly the southeastern part of the state. A few snakes can handle higher elevations, the smooth green snake up to 9,000 feet and the wandering garter snake to 11,000 feet.

Dropping temperatures in fall trigger snakes to move into hibernation dens until the ground warms in spring, when they emerge and begin seeking a mate. So tied are some snakes to the cycle of seasons that they can't breed until after undergoing a period of cooling and lowered metabolism.

Dating And Mating

We may not relate snakes to romance, but male snakes do court females, which helps overcome her predatory instincts so she will mate with rather than attack the male. Male rattlesnakes spar with each other in pushing and shoving contests (though hitting below the belt is hard to determine). Most snakes lay leathery-shelled eggs in a nest but some bear live young. Some species retain the eggs within a shell inside the mother. Garter snake embryos go even further and develop a placenta with the mother.

Serpentine Hunters

All snakes are meat-eaters. Considering they have no arms, legs, wings, or talons, snakes are surprisingly diverse in their strategies for catching and killing prey. Rattlesnakes, of course, paralyze their prey with venom injected with a bite. Racers dart after their prey, grabbing small animals with their jaws. They may pin prey to the ground with a loop of their body. Western hognose snakes dig toads and lizards out of the ground with their shovel-like snouts. Bullsnakes are constrictors, grabbing prey with their jaws, then wrapping their coils around the animal and crushing it until it suffocates.

Look Ma, No Hands

A lack of limbs hasn't kept snakes from doing much. They may not play baseball, but they can climb trees, swim, and move extremely fast across the ground. Most snakes have a single line of scales on their undersides that works as a set of contact points for locomotion, sort of like a tank tread. Rhythmic contractions along the snake’s body allow it to push along a surface by lifting parts of the body and pushing off from the contact points. The familiar serpentine motion involves a continuous forward "S" movement. In concertina locomotion, the animal lifts and reaches out with the head and leading part of the body, then brings the rest of its body up to join it. A sidewinder (none inhabit Colorado) lifts and moves the curves of its body, rather than its head, in the direction of travel. Snakes climb trees by lifting from the ground and finding contact points on the tree trunk. They swim by lifting and pushing themselves quickly across the water, much as a swimming person stays afloat by exerting energy across the water surface.

Pits And Tongues

Have you always wondered why snakes flick their tongues in and out? They "smell" the air with their tongues, picking up tiny odor particles that they transfer to a highly sensitive chemical receptor, the Jacobson’s organ, in the roof of the mouth. Some snakes also "see" heat (infrared light) using sensitive organs located in pits on their faces. Rattlesnakes, which belong to a family known as pit vipers, are so sensitive to heat they can detect a temperature change of .003 degrees Celsius in a tenth of a second, very handy for detecting warm-blooded prey.

Yellow-bellied racer.

Don't Get Rattled

“Kill it!” is a common response upon seeing a snake, but killing animals just because they frighten us doesn't make sense. Even poisonous snakes have a role to play in Colorado's ecosystem and are part of our states natural heritage. Not only are the majority of snakes harmless to people, they actually benefit us by eating pests that destroy crops and stored food. Garter snakes eat insects while bullsnakes help by eating rodents. In turn, snakes (and their eggs) are eaten by many other species, from skunks to great blue herons to eagles.

The popular focus on snakes as venomous is out of proportion to the actual threat. Only two species of poisonous snakes inhabit Colorado—the western rattlesnake (with two subspecies, the prairie and midget faded rattlesnakes) and the massasauga (pronounced mossa-sogga). [Note: As of 2007, the prairie rattlesnake is considered a separate species.] While venomous snakes present a danger and people should be aware and cautious when in rattlesnake habitat, the aggressive pursuit and killing of snakes is not only unsound ecologically, it is illegal. A statutory provision allows for the killing of rattlesnakes if they are felt to be an imminent threat to human life or safety. Killing a snake just because it is venomous is against the law. It is also illegal to kill a protected snake, like a bullsnake, even if you mistake it for a rattler.

Give Snakes A Break

All snakes in the state of Colorado, except the prairie rattlesnake, are nongame species and protected by state law. It is illegal to kill them or take any of them from the wild for barter, sale, or any commercial purpose. Up to four individuals of the following species, not to total more than 12 animals, can be collected to be kept as pets: racer, western hognose snake, bullsnake, western terrestrial garter snake, plains garter snake. The rules also strive to protect native snakes from genetic mixing and from introduction of disease. No non-native snakes may be released in the wild and natives can be returned to the wild only within 10 miles of where they were captured, and then only if they haven't been in contact with animals from other geographic areas.

Even if you have an aversion to snakes, perhaps some at-a-distance admiration will help you appreciate these unique and fascinating creatures. Without them, Colorado's ecosystem just wouldn't work quite right.

Next: Fear Of The Serpent

(The information contained in these issues of Colorado's Wildlife Company was accurate at the time of original publication. Situations and circumstances described, staff positions, contact information, and dates of some events may have changed in the interim. Present knowledge and understanding of biological and behavioral facts and information may also be different than presented here.)

Last Updated: 6/26/2007 11:17 PM