Catching Rock Iguanas: Easier Said than Done!

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Corinne PisacaneThis year I traveled to the Turks and Caicos Islands to study wild rock iguanas. The Turks and Caicos rock iguana Cyclura carinata is endemic to this Caribbean country and is critically endangered. Our team flew to the island of Providenciales, the main hub for tourist travel. From there we continued in a much smaller plane across the beautiful and shallow waters of the Caicos Bank to our final destination, Big Ambergris Cay. This island, located about 40 miles east of Providenciales, is diminutive in size, measuring about 4 miles (6 kilometers) long and only 1 mile (1.6 kilometers) wide. Its highest point is less than 100 feet (30 meters) above sea level. In addition to the iguanas, this secluded island hosts a number of private residences, and there are plans for a large housing development, which poses a potential threat to iguana habitat on the island.

During my time on Big Ambergris Cay, I was involved with a graduate student’s dissertation project involving iguana capture, relocation, and the subsequent examination of homing abilities (among a number of other iguana-related activities!). Every day we set out after it warmed up enough for iguanas to come out of their nooks and holes. Once we located individuals of interest, we set about stalking them. A number of our team members then attempted to catch iguanas of interest with varying degrees of success. Sometimes the lizards were just too fast and would elude our attempts with ease!

Once caught, our next challenge was to try to take a blood sample from each iguana to measure baseline stress hormones. From the moment we caught each iguana, we had exactly three minutes to successfully collect the blood. Any time over three minutes meant that stress hormones (or glucocorticoids) had already reached the iguana’s circulation, meaning we were measuring its stress response to the capture, which was not our goal. As you can imagine, this made for a very exciting three minutes!

If we were not successful, the iguana would be released and not considered as part of the study. If we did succeed, the iguana was then numbered using a system of color-coded beads strung through Spectra line and placed on both sides of the iguana’s dorsal crest between the shoulder blades. This dorsal skin is similar to that of our earlobes, and the stringing of the beads is thought to feel much like piercing one’s ears. Once we were finished marking individuals with beads, each iguana was also fitted with a small radio transmitter to enable future tracking of their movements on the island.

After the identification beads and radio transmitter were secured, iguanas were released at their point of capture and tracked for two weeks to determine their home range. Then they were recaptured and relocated to a different study site just under a mile away to determine if relocation might be used to successfully mitigate future development. As soon as they were released, the race was on! Equipped with radio-receiver equipment, researchers tracked the movements of the iguanas daily to investigate where they went. It appears that adult iguanas can usually find their way home, although how they do so is still not fully understood. By contrast, the homing skills of juvenile iguanas don’t appear to be as developed, and they usually stay put in their new home. For this reason, juvenile iguanas make better candidates for relocation than adults.

Alongside all the capturing and relocating of iguanas, our team also processed all the blood samples collected. This was no small task, as the logistics of processing blood on a small Caribbean island are very involved and time sensitive. Samples had to be frozen immediately, which required transferring them from a portable mobile cooler, carried by each researcher, to a larger cooler on a golf cart (the only mode of transportation around the island!) and then, finally, back to one of our rooms where we’d set up a mobile laboratory. Overall, this was quite an operation! Picture at least half of a dorm room set up as a temporary lab with collection tubes, a centrifuge, slide-staining equipment, and blood-draw needles.

Having traveled to a number of tropical places, I had expected the Turks and Caicos landscape to be all soft sand and friendly flora, with iguanas living in a beach environment. How wrong I was! All this capturing, relocating, and tracking takes place on volcanic-like ground that can quickly tear up ordinary shoes. The ground is also uneven and makes capture and tracking a slow and strenuous process. In addition, the small shrubs and trees are full of thorns and are quite abrasive. As a result, we always wore long pants and covered up at all times, making the work more challenging as it got extremely hot outside. Thick-soled shoes were also critical if we were to move around quickly enough to capture iguanas and avoid large thorns entering the soles of our feet. While we find it difficult to deal with this kind of environment, the iguanas have evolved to be perfectly suited to it.

This type of research is critical to gain a thorough understanding of the biology and behavior of the Turks and Caicos rock iguana. As with most endangered species, we need to be diligent about setting aside the necessary habitat for these amazing reptiles. Rock iguanas throughout the Caribbean are in danger of losing their habitat as a result of human-related pressures. I learned a great deal while on Big Ambergris Cay and am very grateful that I could be involved with iguana conservation in such an amazing habitat!

Corinne Pisacane is a senior research technician for the San Diego Zoo Institute for Conservation Research. Read her previous post, ISWE: Cheetah Pseudopregnancy?

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