Let Loose the Tortoises of the Sandhill!

For
those of you who have faithfully followed our newsletter over the last several
months, you may know that June 2012 marks the start of our gopher tortoise
radio telemetry project! Last August, The Orianne Society, in partnership with
the Georgia Department of Natural Resources, translocated 32 tortoises from a
private property — that was slated for conversion to agriculture use — to the
Orianne Indigo Snake Preserve in Telfair County and the Yuchi Wildlife Management
Area in Burke County, Georgia. The goal of these translocations was to enhance
the tortoise populations at each site. To determine the success of these translocations,
The Orianne Society, again in partnership with Georgia Department of Natural
Resources, will use radio telemetry to determine if translocated tortoises take
up residency in their new homes.

It
sure seemed like the tortoises were ready to get out! At each pen, they had
worn down a smooth track just inside the fence, as they no doubt tried to find
an escape route. This was precisely the reason why we used the pens to hold the
tortoises before their release. The technique of using pens or enclosures to
hold translocated animals is called “soft release,” in contrast to simply
releasing an animal at a new site (referred to as a “hard release”). In the
early days of animal translocation, hard releases were most commonly used.
However, hard releases do not give the animal a chance to acclimate or become
familiar to its new surroundings. As a result, many translocated animals
released through a hard release move rapidly away from their release site and continue
moving long distances. These movements may put them at risk from predators or
other causes of mortality (like roads). Animals released during hard releases
may have low survival rates and the translocation may ultimately fail.

However,
research on translocations employing soft releases show more promise. For
example, previous research on translocated tortoises in South Carolina found
that keeping the tortoises in pens for up to a year resulted in more tortoises
taking up residency near the release site than when tortoises were simply
released with penning. Researchers translocating tortoises often dig “starter
burrows” for tortoises inside the pen to provide them with an immediate refuge.
In our pens, we used a gas-powered auger to drill short (about three feet long)
starter burrows for our translocated tortoises. The tortoises seemed to take to
these starter burrows and by June 2012 many of the starter burrows had been
excavated into full size, well-maintained burrows. There were even some new
burrows that the tortoises had dug themselves. These were all good signs that
the tortoises were starting to settle down and establish residency. But the
real test would come when we pulled the pens and attached the transmitters.

During
the first week of June, our new Orianne Society field technician, Brent Sparks,
and I set out to capture each translocated tortoise at our Preserve. Although
we released 16 tortoises into the pen, we found 20 burrows, indicating that
some tortoises had dug and used multiple burrows over the last ten months. To
determine which burrows had tortoises in them, we used a burrow camera, a
camera attached to the end of a long plastic tube, to “scope” each burrow. If the
burrow was occupied, we placed a Havahart® live trap, like one might use to
trap raccoons or opossum, at the entrance of the burrow, covered the trap with
burlap to provide shade for the tortoise, and sat back and waited.

Actually,
very little sitting was involved because we also needed to scope and trap
several resident tortoise burrows to act as a control group. By attaching
transmitters to several resident tortoises we can compare the movements, home
range size, and habitat use to that of the translocated tortoises. This lets us
formally determine if the behavior of the translocated tortoises is different,
and in what ways, from what we would expect from resident tortoises. When we
captured a tortoise, we weighed it, took many different shell measurements, and
marked it with a unique shell notch and a PIT tag. We then selected 10
translocated tortoises and eight resident tortoises to receive a radio
transmitter. These transmitters were glued to the back of the tortoises’ shell
(the carapace) using a quick-drying epoxy putty. The antenna of the transmitter
was also glued to the carapace so that it would not get caught on roots or
other vegetation. After the transmitter was affixed, we released each tortoise
back at the same burrow we captured it at. We then repeated these procedures at
the Yuchi Wildlife Management Area.

Although
the telemetry study is a mere two weeks old, we have already had some
interesting results. Most of the translocated tortoises at both sites have
remained within a few hundred meters of the pen, and many of these tortoises
have dug brand new burrows of their own. This is an encouraging sign as it may
mean that these tortoises will take up residency near the release area.
However, we have had a few translocated tortoises move further. Two
translocated tortoises at Yuchi have moved over 500 meters from the pen (one of
them moved 950 meters!) in just two weeks. But the greatest movement so far
goes to a translocated female at our Preserve who moved over two kilometers
from the pen in two weeks. The last time we located her she had not dug a
burrow but was just resting under some leaf litter in a pine stand. It is still
too early to tell if these tortoises will not take up residency or if any other
tortoises may move further away from the release area. That is the exciting
part about conducting scientific studies on wild, free-ranging animals:
everyday holds a new surprise! Stay tuned for future updates on the
translocated tortoises!