Catching Rock Iguanas: Easier Said than Done!

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?


Lizards of Guatemala

A large male Guatemalan beaded lizard relaxes in one of the outdoor breeding pens.

I was recently in Guatemala for the 15th annual meeting of the International Union for the Conservation of Nature (IUCN) Iguana Specialist Group (ISG). Thank goodness for acronyms! As the name implies, the group is focused on the conservation and preservation of iguanas. These large, herbivorous lizards are found throughout much of the New World’s tropics and subtropics. Many iguana species are threatened with extinction due to hunting (apparently they taste like chicken), habitat loss associated with agriculture and development, introduced predators, road kills, and other human-associated threats.

Part of the meeting included a workshop focused on local iguana species, one of which occurs in Guatemala’s Montagua Valley. After the meeting and workshop, the group took a field trip to this valley to see these iguanas and to visit the conservation-breeding program for one of Guatemala’s other rare and endemic species, the Guatemalan beaded lizard, a close relative of the Gila monster found in the deserts of the American Southwest.

Thanks to the efforts of local conservationists, the future for both the iguanas and beaded lizards of the Montagua Valley is looking brighter.

Glenn Gerber is head of the San Diego Zoo’s Caribbean Regional Program. Read his previous post, Iguanas: Why Move?


Iguanas: Why Move?

Turks & Caicos iguana

Late 2011 marked the first in a series of experimental iguana translocations on Big Ambergris Cay in the Caribbean’s Turks & Caicos designed to determine the conservation value of moving these large, endangered lizards out of areas slated for development to areas on the island that will not be developed. At first glance you may find it difficult to question the value of moving animals like this. Then again, why wouldn’t you move animals out of the bulldozer’s path? Well, what if the translocated animals simply return home? Or what if their survival in their new habitat is very low? Both of these outcomes are actually quite possible.

Iguanas are territorial animals with small home ranges, and they live a long time. They know their territories well and have invested a lot of time and energy establishing themselves in these areas. This means that animals moved away from their home areas may be highly motivated to return. It also means that iguanas moved to a new area may find they are not welcome by the iguanas already living in that area.

To test these ideas, we moved adult and juvenile animals of both sexes and attached radio transmitters to them to follow what they did. Five out of 12 adults moved (3 males, 2 females) successfully returned to their home areas, and all of those that didn’t return home had tried to. All of the adults moved also lost weight, an indication that they were stressed by the move.

In contrast, none of the 12 juveniles moved returned home, although some did make movements in that direction. The juveniles also lost less weight than the adults, suggesting they may be better candidates for such translocations. To determine if these conclusions are valid, we will need to repeat this experiment to increase our sample sizes. In the end, we will be able to implement a conservation management strategy that makes the best use of limited resources and has the best probability for success.

Glenn Gerber is head of the San Diego Zoo’s Caribbean Regional Program. Read his previous post, Turks Island Boas.


A Significant Blue Birth

The San Diego Zoo’s Applied Animal Ecology Division is pleased to announce the hatching of a critically endangered Grand Cayman blue iguana Cyclura lewisi. This little female iguana hatched out of her egg on September 13, 2008, after an incubation of 92 days at 86.5 degrees Fahrenheit (30.3 degrees Celsius). She weighed only 1.58 ounces (45 grams) at hatching—a tiny little girl compared to males of her species that can grow to over 18 pounds (8 kilograms) as adults! Although our little girl is gray in color now, as most hatchlings are, adults of the species can become a beautiful powder blue color.

This iguana was a very lucky animal. About three-quarters of the way through incubation, her egg formed a small crack and started to leak fluid. This is a rare occurrence and can be caused by too much humidity, a thin shell, or many other factors. I patched the shell with plastic wrap and tissue glue and crossed my fingers. A few weeks later, I got the word that the iguana had hatched, and I ran over to the incubator room to see her. She looked good, although she had a distended belly, which usually means she hatched a bit too early and wasn’t able to absorb all of her yolk. I took her to the vets at the Harter Veterinary Medical Center, and due to the distended belly and a slight injury to the eye that probably happened during hatching, we decided she would stay with the vets. Internal yolk can usually absorb on its own as long as the animal is kept quiet and warm, but sometimes it can become infected and can even be lethal. After a week of excellent veterinary TLC, the little iguana absorbed her yolk, and her eye was healed up. She is currently waiting to be housed in the new iguana building that is near completion in an off-display area of the Wild Animal Park (stay tuned for that blog!).

Grand Cayman iguanas are considered to be the most endangered lizard in the world. Loss of habitat, introduced predators, feral animals that compete for resources, and cars all contribute to the iguana’s decline. At one point, there were as few as 20 animals left on Grand Cayman, but thanks to captive breeding, headstart and release protocols, and a new reserve system on the island, Grand Cayman iguanas are slowly starting to repopulate the wild.

Jeff Lemm is a research coordinator for the San Diego Zoo. Read Jeff’s previous blog, Frog Blog—What’s Hoppenin’?