A Snake With Coats of Many Colors

As a naturalist interested in learning about the incredible diversity of life, I constantly have to deal with the difficulties of identifying animals and plants of different but related species that closely resemble one another. With the common rat snake Elaphe obsoleta in the east we have a different problem- within one species there is a wide variety of types in different geographic locations. Thus from New England to middle GA it is the black rat snake; in the southeastern coastal plain to FL it is the yellow rat snake. Other forms are found in the west and extreme southern FL. There is also a separate southeastern species, the red rat snake or corn snake.

All rat snakes come out of the egg with a rather similar grayish color pattern with blotches. Over time they assume the adult pattern of nearly all black with white flecks or yellowish with stripes. Black rat snakes seem very obvious against a green background and would not seem to be camouflaged as would the yellow rat snake. Of course this depends on the background and at night or against dark bark, black might be a means of camouflage. Stripes are sometimes interpreted as a design to confuse the attack of a predator which would find it difficult to fix on a target of moving lines. Stripes also break up the body outline when the snake is resting in a tree or bush.

Rat snakes lay eggs and these incubate for about two months; the hatchlings are likely eaten by many predators. The snakes eat a wide variety of prey from lizards to birds and eggs to mammals. Probably there is some specialization in local situations whereby snakes imprint on one type of common food early in life and prefer that later. I have always been surprised that black rat snakes on our VA farm generally refuse to eat mice in captivity but eagerly eat young birds. We have had to place protective baffles on our bird houses since otherwise black rat snakes will enter them and eat the young. Yet in FL yellow rat snakes readily accept mice and others have reported that their black rat snakes will eat mice.

In our stewardship of the land we should strive to accept the natural roles of all portions of the food web. Yet many of us have problems in allowing predators to eat our beloved birds. Certainly we should not make any “moral” judgments about wild animals and natural predators cannot be considered “bad.” The natural world must be allowed to function as normally as possible. However I do make a concession to my wife’s dislike of having avian predators in the form of large snakes around our yard by moving them elsewhere.

Bill Dunson, Englewood, FL & Galax, VA

Bill Dunson

About Bill Dunson

Bill Dunson, born in rural Georgia, skipped 12th grade and went directly to Yale. Bill subsequent-ly received a PhD in Zoology from the University of Michigan, studying softshell turtles. Bill is Professor Emeritus of Pennsylvania State University thanks to a career spent entirely at that institution, teaching and doing research on the physio-logical ecology and ecotoxiciology of reptiles, amphibians and fish. Always curious about nature, Bill has dedicated his life to learning and sharing his knowledge with others. He has served on many advisory boards here in Southwest Florida to preserve the water that gives life to our region.

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