RADIATION AFFECT TURTLES?
once conducted research in which you attached metal tags that emitted
gamma radiation to shells of living turtles. You also X-rayed turtles.
Werent these techniques detrimental to the health of the turtle?
John Byrd, an award-winning environmental educator in Tennessee, sent
me the question asked by members of an environmental book club he belongs
question about X-rays and turtles stemmed from ecological research projects
I conducted for many years. Radiation from X-rays has no known positive
effects on individual turtles, but no evidence has been forthcoming
of any permanent harm. Unquestionably, the technique ultimately has
saved many turtle lives. Not unlike a dental X-ray, which can lead to
healthier teeth in people, 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.
use X-radiography, a basic medical tool, to study reptile eggs whose
shells contain sufficient calcium to be detected by X-ray photography.
All crocodilians and turtles and most snakes and lizards lay eggs. Originally,
we brought turtles into the laboratory to X-ray them. Today, research
ecologists use portable X-ray machines, enabling them to gather pertinent
data about numbers and sizes of eggs while in the field. In either case,
animals are returned unharmed to their habitat.
set of studies conducted by scientists at the University of Georgias
Savannah River Ecology Laboratory documented how many turtle eggs were
laid outside the periphery of freshwater wetlands. The research reinforced
an important principle: a wetland extends functionally far
beyond the waters 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. A notable
side note: Before X-ray techniques were developed, scientists would
dissect turtles to determine how many eggs they had. Clearly, X-irradiation
causes less harm to the turtle.
sampling technique is especially important in ecological studies in
which loss of even a single specimen is undesirable. Studies in New
Zealand on internationally endangered tuataras, which look like large
lizards, relied on X-ray photography to obtain information on when tuataras
had eggs and how many. Investigators were able to gather critical information
on egg production, which was necessary for understanding population
growth patterns in these unusual animals teetering on the threshold
reference to attaching radioactive metal tags to turtles was based on
studies we conducted many years ago before federal regulations concerning
uses of radioactive materials became as stringent as they are today.
We used a nonmagnetic metal called tantalum.
its isotopes, tantalum-182, emits gamma radiation. After drilling a
tiny hole in the shell margin of a turtle, we inserted a half-inch piece
of the radioactive metal that was the diameter of a paper clip. A turtles
outer shell is biologically similar to our fingernails, so the turtle
was not physically harmed. We sealed the tiny opening with glue, then
each turtle was released where it had been caught.
the next several days, we used an instrument comparable to a Geiger
counter as we drove around the margins of wetlands we were studying.
We located turtles buried in dirt or sand hundreds of feet away from
water. We had to be within 30 feet of a buried turtle to detect the
radioactive signal, but by patrolling in an ever-increasing spiral away
from a wetland, we eventually located them. Back then, these aquatic
species were only known to come on land to lay eggs. Until our use of
tantalum tags, no one knew they also hibernated on land.
researchers attach small transmitters and use radiotelemetry to locate
released animals, but the early techniques yielded new information otherwise
unobtainable at the time. Meanwhile, should another question be what
were the effects of gamma radiation on the investigators?
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