Savannah River Ecology Laboratory
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Herps of SC/GA
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Stop #10: St. Augustine, FL
Featured Herp: Corn Snake (Elaphe guttata)

East Aiken arrived near St. Augustine on November 8, 1999. Sometimes it can be difficult to find accommodations for such a horde of youngsters—fortunately Faver-Dykes State Park, with its primitive youth camping area, was nearby. Florida has about 150 state parks, many of which will be useful to the East Aiken classes in the weeks to come.

The Spanish settled St. Augustine in 1565, 42 years before the English colony at Jamestown, Virginia, and 55 years before the Pilgrims landed on Plymouth Rock in Massachusetts; it is the oldest permanent European settlement in North America. East Aiken will have plenty of history to explore in this area.

Faver-Dykes State Park also has many interesting natural habitats to explore. One of these habitats is the pine flatwoods, home to many neat critters, including our featured herp of the week, corn snakes.


Corn Snakes (Elaphe guttata) and Food Chains

corn snake closeup of head

Ecology, as an area of scientific study, examines the relationship among organisms and their environment. At the heart of any research on the ecology of an organism there must be an understanding of "food chains" and "food webs." This is especially true in the case of animals—if you don’t know both what an animal eats and what eats the animal, then you can’t really understand that animal’s ecology.

Snakes provide a good illustration of food chains—a plant uses energy from sunlight to grow, sustain itself and make seeds; a mouse eats the seeds; a snake eats the mouse. Simple enough. A longer "chain" might include a kingsnake eating the first snake, and a hawk eating the kingsnake. An examination of food chains reveals that most are usually only three, four or five "links" long. One possible reason that food chains must be relatively short was noted by ecologists years ago. The reasoning is basically that because so much energy is "lost" at each level or link in the chain, then after several links there just isn’t enough energy left to sustain an animal population. For example, when an herbivore (plant eater) consumes a plant, most of the usable energy from the plant is used just to keep the plant-eater alive. Only about 10% of the original energy from the plant ends up as "meat" in the herbivore that can then be consumed by a meat-eater (carnivore).

corn snake on a log

The same rules of physics apply to the carnivore, and so most of the energy in the food it consumes is similarly lost or used up just to keep itself alive—only 10% or so ends up being available to yet a bigger carnivore that wants to feed on it. The loss of so much energy (90%) at each link in the chain basically explains two additional ecological observations—in general, animals at the higher levels in the food chain are 1) bigger than animals at lower levels, and 2) less numerous than animals at lower levels. As the original energy from the sun gets more spread out (in the form of small packets of energy, such as an ant or caterpillar or chickadee), predators must usually be bigger than prey both to move over large areas to find enough food, and, once they find it, big enough to kill it. Also, since the total pot of energy available as food is far less at each link in the chain (called a trophic level), fewer animals can be supported.

four-link food chain: plant-herbivore-predator1-predator2
Typical short chain found in nature.
13-link chain
Most food chains in nature are short -- 3, 4, or 5 links -- and none are as long as this one. Ecologists try to understand the causes of patterns like this in the natural world.

As is the case in most any topic in ecology, not all scientists agree that the limitations of energy flow through the food chain can explain the length of the chain. Unanswered questions and scientific arguments are just two of the reasons that ecology is a fascinating field of study.

Because all snakes are carnivores, their food chains will be at least three "links" long: plant → animal prey → snake. Adult corn snakes are a prime example of this simple, short food chain. Juvenile corn snakes, which feed on treefrogs and lizards instead of mice, are in food chains that have an additional link: plant → insect → lizard or treefrog → snake.

southeastern distribution

>Download the Corn Snake Fact Sheet

Links with additional information on corn snakes:
Care of corn snakes
Corn snakes in North Carolina

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