Saving the Iguana Islands of Turks and Caicosby Giuliano ColosimoRSPB are currently working in partnership to secure the future of the Critically Endangered Turks and Caicos rock iguana and to save the Iguana Islands of the Turks and Caicos Islands, a UK Overseas Territory in the Caribbean. Here is a guest blog from Dr Giuliano Colosimo from San Diego Zoo, one of our partners, on the progress of the project so far:
Some 150 Km north of the Dominican Republic, at the southern end of the Lucayan Archipelago, lie the Turks and Caicos Islands (TCI). This British oversea territory is home to many endemic species of vertebrates. The most notable and charismatic is the Turks and Caicos Rock Iguana, Cyclura carinata (Fig. 1). This species is listed as Critically Endangered in the IUCN-Red List of Threatened Species. Human-mediated habitat destruction and introduced invasive predators (such as feral cats, dogs and rodents) represent two of the main threats for this native reptile.
Figure 1 Male of Turks and Caicos Rock Iguana (Cyclura carinata) foraging on some 7 years apple fruit.
In April 2017 the Royal Society for Protection of Birds (RSPB) in collaboration with the TCI-Department of Environmental and Coastal Resources (DECR), the TCI-Department of Agriculture (DoA), the TCI-National Trust (TCNT), the Institute for Conservation Research (San Diego Zoo Global), and Ambergris Cays Facilities Ltd., launched a 3 year project, funded by the UK Government’s Darwin-Plus Initiative, entitled “Saving the Iguana Islands of Turks and Caicos”. The aim of this project is to secure the future of the Turks and Caicos Rock Iguana through the establishment of effective biosecurity plans and the monitoring and identification of suitable islands for future restoration of the species (Fig. 2). Now, one year and a few months in to the program, we are happy to share some of the achievements, challenges and future plans of the ongoing project.
Figure 2 Elizabeth Radford (RSPB), during the presentation of the project in April 2017 in the TCI. All project partners and stakeholders, including two government ministers, attended the event.
Two of the largest remaining natural populations of TCI Rock Iguanas are found on Little Water Cay (LWC) and on Big Ambergris Cay (BAC; Fig. 3). Other islands, scattered throughout the TCI archipelago, still harbor viable iguana populations, but LWC and BAC were prioritized in this project due to their strategic importance as last natural strongholds of this formerly widespread and abundant lizard. LWC (also known as The Iguana Island) is one of the most accessible sites for visitors to see the iguanas in their natural environment. It is, therefore, an important tourist destination that deserves special conservation attention. BAC, on the other end, is a privately-owned island. This island, thus, doesn’t experience the same volume of tourists visiting it on a daily basis. At the same time, BAC is currently under intense development, and could soon become a rather important tourist avenue as well. Probably due to its development, the island, formerly free from rats, is now facing the risk of a potential invasion.Within the framework of the Darwin-Plus funded project our initial goals were to: i) monitor LWC and BAC as well as some of the offshore islands around them to assess the presence of feral cats and rodents, some of the most impactful invasive species worldwide. This information is vital for the formulation of appropriate biosecurity plans; ii) collect data on the iguana populations on LWC and BAC. Both islands have been part of a long-term population-monitoring program. Due to the increased human activities on both sites we wanted to gather data on the possible impact of human-lizard interactions and how these may be affecting the iguanas’ physiology, morphology and behavior; iii) contribute to building capacity of local organizations to improve the conservation chances of this critically endangered lizard.
Figure 3 Map of the Turks and Caicos Islands. Little Water Cay (LWC) and Big Ambergris Cay (BAC) are highlighted (the map was downloaded from Google Earth Pro).
Feral cats and Rodent monitoring Cats and rats were already present on LWC. A rat control protocol had already started on LWC in 2015 as part of the EU-BEST funded project. Parallel to this, a privately funded project begun during the summer 2017 with the specific objective of eradicating cats from LWC as well as from two of the islands north of it: Water Cay and Pine Cay (Fig. 3). Unfortunately, right before the completion of the cat eradication project, i.e., when the data indicated the presence of only one cat left in the wild, hurricane Irma hit the TCI and all the researchers and workers on the eradication project had to leave. The project is bound to recommence in 2019. During this interruption we conducted our survey to have a better, up-to date, idea of where rats and cats are found around LWC and BAC. This information is extremely important because it will pave to way for formulating an appropriate biosecurity protocol that would prevent cats and rats to be reintroduced on island where they will be eradicated.Sometimes it is possible to see tracks of rodents, cats or other invasive animals directly on the beach. Unfortunately, not all islands in the TCI have nice and white beaches that can be used as natural tracking corridors. Moreover, the wind and the action of the waves can easily erase any track in matter of minutes. On top of that, seeing a few tracks on a beach doesn’t provide a good estimate of the magnitude of the infestation. At the same time, looking for feral cats or rats during the day amid the shrubby and tangled vegetation can be a daunting experience. Both cats and rats usually forage at night and seeing them during the day is very rare. On the other hand moving about the razor-sharp rocks and solution holes using flashlights at night is not really recommendable. Therefore, to monitor different islands for the possible presence of these invaders, we took advantage of two different techniques.We first used Tracking Tunnels (Figs. 4, 5 and 6). The idea is simple and very effective: a white cardboard with a black ink-pad in the middle is baited with something that rats or cats are attracted to (did you know that rats go crazy for peanut butter?). The baited cardboard is then placed inside a foldable plastic tunnel, and the whole structure is anchored to the ground using sticks or rocks. The tunnel is left for three or four nights and is checked on a daily basis to make sure that the bait is still there and available. When a rat, or another animal, passes through the tunnel, attracted by the smell of the bait, it leaves behind very distinct track-marks on the white portion of the cardboard (Fig. 5). This monitoring technique is a cost- and time-effective way to assess an area for the possible presence of rodents and/or other animals. Sometimes, though, animals that are not the target of your monitoring are lured inside the tracking tunnel by the bait. During our monitoring we found out very quickly that iguanas, just like rats, are very fond of peanut butter!!
Figure 4 Dr. Giuliano Colosimo, PostDoc with SDZG, preparing a camera-trap and a tracking tunnel prior to installation. (Photo: S. Havery)
Hoping to get some additional evidence about the presence of cats or rats we also deployed Camera Traps. These are motion-activated devices that start recording videos or pictures when their sensors detect the presence of something in front of them. It is often useful to bait the area in front of the camera with something that would attract the species of interest. We used canned-sardines to lure in feral cats and/or rats. While visioning the images collected we learnt that iguanas are not only fond of peanut butter, but they also seem to like sardines very much!! Another problem we incurred in while using camera traps is that they can be very sensitive to movements. Moving leafs and branches can trigger the camera. In the TCI the breeze is almost always blowing and plants are always waving. This is a relief for those conducting field work, but it also translates to thousands of pictures that have to be post-processed and analyzed looking for “intruders”.
Figure 5 Tracking tunnel prints observed (left to right: Lizard, Mouse, Rat, Rat). (Photo: S. Havery)
Figure 6 From left to right: Dr. Glenn Gerber (SDZG and Caribbean program head), Joe Burges (Field Zoologist and reptile expert) and Sarah Havery (RSPB). Sarah is holding a tracking-pad covered in rat tracks.
Using the SDZG skiff and a boat provided by DECR we managed to survey five cays in the proximity of LWC (Donna, Mangrove, Fort George, Lizard, and Bird Cay) and six cays around BAC (Bush, Little Ambergris, Six Hills, Fish, Middleton and Long Cay). Unfortunately we found evidence of rats on many of the surveyed cays with the exception of Lizard, Bush, Little Ambergris and Six Hills cays. On Middleton Cay we didn’t find any evidence of rats, but we found evidence of mice.
Figure 7 Night-frame from one of the camera traps we left over night on Long Cay. Can you find the intruder?
The analysis of all collected images from the camera traps didn’t highlight the presence of cats, although we had visual evidence of the presence of rats (Fig. 7). Unfortunately, we also found evidence of rats on BAC. Thanks to the slow development of the past few years BAC managed to remain free from rats and cats. With the recent developments going on a lot of construction material and supplies are brought by big barges to the island. Rats, and sometimes even cats, can hitchhike on those barges, and in fact we suspect that the responsible for the rat tracks we found on our first visit to BAC in April 2018 arrived hitchhiking on those barges.
Monitoring of iguanas on LWC and BACIn an effort to understand how human interaction may be affecting the physiology, morphology, and behavior of iguanas, we collected iguanas’ samples from LWC and BAC. Both sites have been part of a long-term mark recapture project started in 1995 aiming to gather important information on iguana population size and demographic characteristics. Upon capture, morphological measurements such as snout-vent length, body mass and cranial morphology are recorded for each individual (Fig. 8). The data are then entered in a database that, at the end of the study, will be used to track individual and population parameters such as growth rate, age at reproductive maturity, sex ratio, longevity and age structure within the population. Along with morphological measurement a blood sample is also collected. The blood is processed to highlight stress level differences between sites where the lizard-human interaction is high as compared to those sites where iguanas are relatively undisturbed. Although the final results from the stress level analysis of samples collected in April 2018 are not yet ready, the morphological data collected so far indicate that iguanas from areas with a high human impact are considerably larger than animals with no or regulated human impact. This suggests that supplemental feeding may be part of the of the human interaction with the iguanas.
Figure 8 Measuring the head length of a male iguana. Most iguanas are relatively docile when morphological measurements are collected, but there is also plenty of feisty iguanas ready to take a bite of whatever comes close to their mouth (Photo: G. Colosimo).
While monitoring iguanas on BAC we also collected data on road kills. Being privately owned and with a low number of tourists, BAC doesn’t have a lot of traffic. In fact, visitors and the local staff on site use golf carts to move about the island. With the current development happening on the island a lot of heavy machinery have been used. Unfortunately, this translated to a pretty high incidence of road kills. In 2018, while performing road transects during two different field trips, we counted 33 dead individuals, with the majority of them being adults. This is an alarming number, especially if we consider that Cyclura carinata iguanas take about 7 years to become sexually mature. We fear that such a high rate of road mortality, should it continue like this, could be unsustainable for the population. This is also because the number of road kills adds up with the number of iguanas that are naturally removed from the population due to predation. In their natural environment C. carinata iguanas have really few predators. When they hatch they can be targeted by falcon-like birds like the American Kestrel, which is relatively abundant in the TCI. Another natural predator, probably the only one capable to predate on adult iguanas, is another species of endemic reptile: the rainbow boa Chilabothrus chrysogatser. During one of our night monitoring we were able to document a rare instance in which an adult boa had predated on an adult iguana (Fig. 9).
Figure 9 Behind the branches, almost entirely hidden by the rocks, it is possible to see a boa constricted around the head of an adult iguana. (Photo: G. Colosimo)
Working in partnershipNo conservation initiative is bound to succeed without the help of local organisations and people. That is why, as part of the project to save the iguanas and their islands in the TCI, we dedicate special attention to build capacity and exchange skills and experiences with the local staff of our partners, Turks and Caicos National Trust, Department for Environment and Coastal Resources (DECR) and Department of Agriculture (DoA) and the local community. Ultimately, the community are the ones going to make a difference for the future of the TCI. Every field season, members of the TCNT, under the supervision of Dr. Della Higgs, join us during our iguana monitoring. The project benefits directly from their participation because they receive additional training (Fig. 10) and update us on some important facts happening on the different islands while we are off site. At the same time, they also organize initiatives directly targeted to the education of the young students in the TCI. For example, during our last field trip in August, we had a special guest joining us during the field sampling and processing of iguanas (Fig. 11). Rocky is the TCI Iguana mascot, as part of a public awareness campaign funded by the EU BEST Initiative. Thanks to him, generations of young students get acquainted to the natural beauty of their local resources, and learn important things about the iguanas. This time, together with Rocky, two of the wardens working for the TCNT also joined us. They helped in the catching, processing and data collection, and we spent a delightful day doing conservation in the field.
Figure 10 George Waters (to the right), an outstanding volunteer who dedicated much time and effort to the iguana project, is training Dimitry (TCNT warden, left) and O’Benson (TCNT warden, center) on how to catch iguanas without harming them.
Figure 11 Rocky, the iguana mascot, holding a little iguana fellow. Together with Rocky is Dr. Della Higgs (TCNT). Dimitry, one of the TCNT warden, is sitting on the chair, ready to start processing the next animal.