Radiation can be good for turtles | ECOVIEWS

Several years ago, Judy Greene of the University of Georgia’s Savannah River Ecology Laboratory took a turtle to a nearby medical facility and asked the staff to X-ray it.

The turtle was not sick; it did not have a cracked shell or broken bones. But that image had far-reaching, invaluable consequences for ecological research: the X-ray clearly showed that the turtle was carrying eggs.

X-ray photography had been used as a tool in human medicine for decades. Because of that turtle’s photograph, X-rays are now used worldwide to reveal highly interesting phenomena about animals other than humans in fields other than medicine. The animals are primarily reptiles; the fields are ecology and biology.

Herpetologists who study the ecology of snakes, alligators, lizards and turtles sometimes need information on the animals’ internal characteristics. For examining the “hard parts” of an organism (e.g., bones, eggs, solid stomach contents), X-ray photography can be a useful technique.

X-ray photons are absorbed by hard, dense material like bone, and structures appear as bright areas on the radiograph (film). Radiographs enable ecologists to gather pertinent data, then return the animal unharmed to its original capture location.

A valuable feature of the X-ray technique is that the number of eggs in egg-laying reptiles can be determined from one year to the next because none need be killed for dissection. Scientists can examine and release live specimens in field studies without harming them or affecting the integrity of the population being studied.

The field of ecology, not to mention the reptiles themselves, has benefited greatly from the use of this nondestructive sampling method by scientists who study reproduction. The advantage for preserving individuals of rare or endangered species is indisputable.

For example, the reptile X-ray technique developed at SREL was eventually used in research on an endangered, one-of-a-kind reptile from New Zealand known as the tuatara. Because researchers used radiography, none of the lizard-like creatures had to be dissected, and a study to determine how many eggs a female laid added to the limited information on reproduction in the species.

An early concern was whether X-rays would harm the study animals. In a series of experiments, some turtle eggs were X-rayed then compared to eggs that had not been scanned. No evidence whatsoever of mortality or mutational effects on baby turtles was found.

Reptiles, particularly turtles, are among the least sensitive animals in the world to radiation effects. And the brief exposure to radiation is apparently inconsequential to a developing turtle embryo.

A similar study was done a few years ago on the eggs of tuataras, with the same results. The effect of X-rays on a mother turtle or tuatara is more difficult to determine. But SREL studies have kept track of frequently X-rayed female turtles and they have continued to lay eggs year after year for decades with no noticeable ill effects.

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Not unlike a dental X-ray for people, which can lead to healthier teeth, finding out when and where reptiles lay their eggs has led to environmental guidelines and regulations protecting entire populations of turtles as well as other egg-laying reptiles.

One set of studies documented how many turtle eggs were laid outside the periphery of freshwater wetlands. The research reinforced an important principle: functionally, a wetland extends far beyond the water’s edge. Hence, land around a wetland must be protected as well as the water itself if its inhabitants, such as turtles, are to persist.

Quantifying egg numbers laid by each species of turtle could not have been accomplished harmlessly without X-radiography. An important side note: Before X-ray techniques were developed, scientists had to dissect female turtles to determine how many eggs they had. Clearly, X-irradiation causes less harm to the turtle.

Though some animals continue to be dissected in the course of ecological research, today's ecologists avoid doing so whenever possible. X-ray technology permits them to conduct certain kinds of research in the spirit of modern-day efforts to preserve natural populations of animals.

Whit Gibbons is professor of zoology and senior biologist at the University of Georgia’s Savannah River Ecology Laboratory. If you have an environmental question or comment, email ecoviews@gmail.com.

This article originally appeared on The Tuscaloosa News: Radiation can be good for turtles | ECOVIEWS