ARE MORE SNAKES AROUND US THAN WE THINK?

by Whit Gibbons


April 8, 2007


I write about snakes each spring when they emerge from hibernation. This year, I asked J. D. Willson, a University of Georgia doctoral student who studies snake ecology at the Savannah River Ecology Laboratory, to provide his perspective. Here is his response.

"A warm spring day is a great time for snake walks. On just such a day several years ago I went to check out snake activity along a local river. Streams and rivers are good places to observe watersnakes as they hunt for fish and frogs in the shallow water or bask on overhanging tree limbs. This particular river was home to a healthy population of northern and brown watersnakes. At some times of the year snakes are rarely seen there; at others you might see several of these harmless serpents in the course of an afternoon’s walk. I felt certain the warm weather would coax snakes out of hiding and provide a satisfying wildlife-watching experience.

"As I walked, I scanned the shoreline for the characteristic blotched pattern common to brown and northern watersnakes. Before long I spotted a large brown watersnake stretched along a protruding snag. I could tell by the lump in her stomach that she (females get much bigger) had recently eaten a large fish and was now warming up in the sun to aid digestion. I was right; it was going to be a good day for snakes.

"As I continued along the shoreline path I began to see more snakes. A large bush overhanging the water held three northern watersnakes in various poses, soaking up the spring sunshine. A tree that had collapsed into the water contained no fewer than eight snakes. Over the course of the next hour I saw well over 100 snakes along about a mile of shoreline. As I walked, I began to wonder how many snakes really lived in that stretch of river and why I didn’t always see them. Just how important was their role in this ecosystem?

"As a herpetologist, I know snakes are secretive. Most spend the vast majority of their time hidden in underground burrows or in logs, tree holes, or other inaccessible places. In fact, herpetologists who use radio transmitters to track snakes seldom see the ones they are tracking. This secretive behavior makes it difficult for scientists to gauge just how many snakes live in a given area. However, as my watersnake experience shows, snake abundance is not always what it seems. Indeed, research has shown that more than 500 snakes can inhabit a single acre of Florida wetland habitat or Kansas prairie.

"Most large, warm-blooded predators are relatively rare because they need large tracts of land to support their prey. For example, sighting a bobcat in the Southeast is an uncommon experience; each bobcat needs hundreds of acres of land in which to hunt. So a high abundance of snakes is especially amazing when you consider that all snakes are predators; they feed on many types of animals from insects, fish, and frogs to mice, rabbits, and birds. Some snakes even eat other snakes. For every fox, bobcat, or hawk in the forest there may be hundreds of snakes. And though we don’t see snakes all the time, their abundance makes them an important part of the food chain. For every rodent eaten by a fox or cat, hundreds may be eaten by rat snakes, corn snakes, and kingsnakes that are common in suburban areas throughout the Southeast.

"As I continued my walk along the riverbank I became increasingly aware of the significant role the watersnakes surely played in this river ecosystem. Certainly they were as important as the otters I had occasionally seen fishing in that same area. And as the snakes themselves are prey for hawks, owls, and other predators, they are probably far more important to ecosystems than meets the eye."

Snakes are a critical part of their ecosystems, but they are unobtrusive. They don't call attention to themselves by trilling, flitting from branch to branch, leaping through the woods, or soaring up above. But if you stroll along a riverbank on a warm spring day and pay close attention, you may be as fortunate as J. D. was.



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