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Big Ambergris Cay

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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?

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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.

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Turks Island Boas

Turks Island boa

It’s difficult to believe that in an environment dominated by ocean and large sharks, the apex land predator in the Turks and Caicos Islands is a small, nonvenomous snake. A really, really big Turks Island boa is 5 feet long (1.5 meters) and weighs a whopping 1 pound or so (0.4 kilograms). Most are much, much smaller, less than three feet long in fact, and weigh only a few ounces. Nonetheless, like most snakes, humans often fear these animals, and malicious killings are part of the reason they are now rare on most islands in the Caribbean Sea. Another reason is predation by introduced cats and dogs, which the boas have no fear of or natural defenses from. Human development and the habitat loss and vehicular traffic that come with it are other reasons.

The boa pictured here is a large female from Big Ambergris Cay, a small island located on the eastern edge of the Caicos Islands. Big Ambergris has the largest remaining population of this species and one of the densest-known boa populations in the world. The island is only about 2.5 square miles (6.5 square kilometers) in area, but population estimates suggest there are over 2,000 snakes there!

Unfortunately, Big Ambergris Cay is now in the process of being developed as an exclusive private resort community. The challenge ahead will be to find a balance between the needs of humans and native wildlife, like the boas. Fortunately, both the government and the developers recognize this challenge and are working with conservationist to ensure such a balance is achieved.

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

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Boas in the Caribbean

Turks and Caicos rainbow boaIn mid March, I spent nine days on Big Ambergris Cay in the Turks and Caicos Islands conducting research on the Turks and Caicos rainbow boa Epicrates chrysogaster. Of course, I wasn’t alone! I was with a team of three volunteer assistants and Graham Reynolds, a collaborator and population geneticist from the University of Tennessee. Our project, now in its second year, is focused on understanding the natural history, genetics, and population density of boas in order to formulate a comprehensive plan for their conservation and management.

Big Ambergris, a 1.5-square-mile (4-square-kilometer) private island, is undergoing extensive development and is believed to support the most abundant population of this species remaining. Fifty-nine boas were tagged in 2008, and so far 103 new boas have been tagged in 2009. Out of 165 total captures to date, only 3 have been recaptures of previously tagged individuals, suggesting the population is indeed very large and dense.

My research on boas received considerable media attention during my recent research trip as well! A film crew from the TV show Timbuktu, a popular animal documentary series in Italy, filmed the team in the field; Graham and I were interviewed about our research with boas (and iguanas) by two local TV channels in the Turks and Caicos Islands; and the Turks and Caicos Sporting Club, which manages Big Ambergris Cay, highlighted my research in a press release.

Turks and Caicos dwarf boaWhile working on Big Ambergris Cay in March, we also found the first specimen of the endemic Turks and Caicos dwarf boa Tropidophis greenwayi greenwayi recorded from the cay since it was described in the 1930s. Several herpetological surveys conducted in past decades failed to record the species on the cay and concluded, in error, that the species had been extirpated from the island. The snake was photographed, measured, tagged, sampled for genetics, and released. If other specimens are found, they will also be tagged so that information can be compiled on this rare and endemic species.

Glenn Gerber is head of the San Diego Zoo’s Caribbean Regional Program.

Here’s more information about Glenn’s study
Here’s more information about boas