The Cold Blooded News

The Newsletter of the Colorado Herpetological Society

Volume 28, Number 10; October, 2001

Relocated, Rambling Reptiles

by Michael Smith

Reprinted from the newsletter of the St. Louis Herpetological Society, Vol.28, No.7, July 2001.
Originally published in Herp News, the newsletter of the East Texas Herpetological Society, December 1999.

My neighbor rarely brings presents, but on an early October day he brought me a surly little gift: a newly hatched Texas rat snake with gaping mouth and rattling tail. It seems that junior had made his way up from our nearby park and was exploring someone's garage. The homeowner didn't see that as a desirable thing. Luckily someone remembered the family down the block that keeps all the snakes, and so the little mouthful-of-teeth was brought to me.

Now I have a great appreciation for the Texas rat snake (Elaphe obsoleta lindheimeri). It is a handsome snake with an incredible ability to survive in areas invaded by humans, and continues to be one of the most successful and common reptiles in north Texas. It also has a well-deserved reputation as one of the "meanest critters" you can find. I have caught a great many Texas rat snakes, and I believe I have been bitten by every single one of them. To be fair, they are not really "mean". If an observer was smart enough to stand and quietly observe, without approaching, there would probably not be a trace of meanness. I do not know this from experience, for I am not smart enough just to observe and let well enough alone. I have to see it up close, and when grabbed, Texas rat snakes are very willing and very capable of defending themselves with well aimed strikes.

So, keeping this snake was not one of the thoughts that crossed my mind. I just wanted to relocate it where it would have a chance at a full lifespan, without being beaten to death in someone's driveway. After a few days, I took it to a stream that cuts through a nearby prairie and watched him crawl away. A couple of years ago I had relocated a bigger Texas rat snake to that same stream and watched her climb steadily and unerringly to the tops of some mature pecan trees. I hope she's doing well, but I don't know. There is a big question about whether relocated snakes do very well.

Many reptiles have a particular area, their "home range", where they tend to stay. If you were to track the individual reptile as it moved about, it would generally stay within this familiar area. Some species stay within very small home ranges, never traveling more than perhaps 20 or 30 yards in any direction. Others may move around within a home range of thousands of square yards or more. What happens when you take a reptile out of its home range, relocating it in an unfamiliar place? If it is the right kind of habitat where it can find the right food, will it simply get familiar with its new surroundings and do fine? Or would it set out searching for familiar landmarks and use up far too much energy traveling around, or get killed because it spent so much of its time on the move?

Several years ago, Erika Nowak was finishing her graduate work, studying relocated rattlesnakes in Arizona (Nowak, 1998). Rattlesnakes found near visitor areas in Montezuma Castle National Monument were routinely relocated, and Nowak wanted to know what happened to these snakes.

A number of diamondback rattlesnakes (Crotalus atrox) were captured and implanted with radio transmitters. Ultimately, she found that the rattlesnakes tended to increase their activity range when relocated. Writing in the Sonoran Herpetologist, Nowak summarized some of the other research on relocating rattlesnakes. In some cases it appears that relocated snakes have high mortality, including a report of relocated timber rattlesnakes following resident snakes to den sites but then refusing to go in, freezing to death just outside the den.

Reports such as this really make one wonder how well it turns out for snakes that we "rescue" and release in an unfamiliar area. If we relocate a snake found in someone's garage, will it get run over trying to find its old home range, freeze to death because it can find no familiar hibernaculum, or perhaps even make it back to the original area and be killed by the homeowners?

Turtles are also relocated at times, but presumably not because humans fear them. In fact, people tend to pick turtles up and keep them for a while. Then the turtle may be released far from its home. Who knows how often a turtle is set free in habitat that is entirely unsuitable for it, and dies a slow death as surely as if it were left neglected in some cardboard box? Even worse, the released animal may carry a new disease into a population of turtles that has no resistance to it. This has been a problem with desert tortoises kept as pets and then released in the United States.

But suppose the turtle is released closer to home, in suitable habitat, without being exposed to any disease during a short period of captivity. Does what we know .about reptile movement patterns have anything to say about this? I believe that it does.

Back in the 1940's, a researcher began studying box turtle (Terrapene carolina) movement by attaching spools of thread to them. As the turtle moved, the thread unwound, tracing the turtle's exact path. Over a period of more than 40 years, she found that the location or size of a box turtle's home range did not tend to change. A number of researchers have found Terrapene carolina home ranges to have a diameter of about 100 to 150 meters (Ernst, Lovich, & Barbour, 1994). Remember that a meter is little over a yard long; a box turtle might never leave an area a little bigger than a football field during its lifespan of 30 to 40 years or more. When out of their home range, most adult box turtles show some homing tendency, moving back in the direction of home. Evidently they orient themselves using the position of the sun, as they are less accurate on overcast days and light reflected form mirrors can get them off course (cited in Ernst, et al., 1994).

I can well remember years ago, when box turtles were more common, stopping to get them off the highway before they were hit. My wife and I relocated a number of turtles down less traveled side roads, hoping that they would not wander back onto the highway. We may have succeeded only in making the turtle's work harder to do what they were already doing: crossing the highway. It's not as simple as we thought. Relocated adult box turtles are likely to move in a more or less straight direction , perhaps (but not necessarily) toward the original home range, and may not re-establish a home range in a new place. This puts them in the paths of various kinds of danger as they try to move across unfamiliar territory. It may also interfere with their finding food and shelter. If we were to find a box turtle on the road now (and unfortunately, this is a rare thing where we are), we would simply move it off the road in the direction it was headed, and not relocate in any more than that.

In this article I have raised the issue of possible harm done when we relocate reptiles. Nevertheless, we often face situations where an individual reptile must be relocated or it will surely be killed. Is there more to learn about whether relocation can be successful: What about babies - do they fare better if they are relocated? I'll try to address these issues in a future article.

References:
Ernst, C.H,. Lovich, J.E., and Barbour, R.W. (1994) Turtles of the United States and Canada. Washington, D.C., Smithsonian Institution Press.
Nowak, E.M. (1998) Implications of nuisance rattlesnake relocation at Montezuma Castle National Monument. Sonoran Herpetologist, 11(1). Pp. 1-4.
Pough, F.H., Andrews, R.M., Cadle, J.E., Crump, M.L., Savitzky, A.H., and Wells, K.D. (1998) Herpetology. Upper Saddle River, NJ. Prentice-Hall.