Report submitted by Kelly A. Bradley, Fort Worth Zoo
The Critically Endangered Anegada Iguana has been the subject of a long-term headstart program, designed to offset high juvenile mortality resulting from the feral cat population on island. Each year hatchlings are brought into a captive facility, reared in safety, and released back to the wild at a larger, less vulnerable size. As of October 2015, over 200 animals have been returned back to the wild, almost a 50% increase in population since the program began in 1997. Project actions fell into three categories: fieldwork, captive facility work, and education. Fieldwork included camera trapping on Anegada to monitor wild/released iguanas, nesting/hatchling activities, and a new initiative to determine if invasive mammals were present on Fallen Jerusalem Island. Researchers supported headstart work by locating nests, collecting hatchlings, and releasing size-appropriate iguanas back to the wild. In addition to monitoring the health of captive animals and working with local animal staff on husbandry, Fort Worth Zoo (FWZ) staff also renovated all the pre-existing wooden cages at the facility. The educational components included generating an informative poster to help the public prevent the introduction of Common Green Iguanas to Anegada, updating graphics at the headstart facility, and conducting the 5th annual Iguana Fest.
Common Green Iguana invasion education campaign. The FWZ and National Parks Trust of the Virgin Islands (NPTVI) designed a poster informing the public about the existence of two distinct iguana species found in the Virgin Islands, and the dangers of moving wildlife (iguanas, mongoose, snakes, and cats) between islands. The poster will be distributed this fall and winter to ferry docks/operators and sailboat charter companies. The poster addresses the greatest problem about Common Green Iguanas (Iguana iguana) — that is the general public is unaware that there are two separate iguana species in the Virgin Islands and the consequences of a Common Green Iguana introduction to Anegada.
A potential Common Green Iguana invasion is a previously unaddressed threat. By distributing education materials to the ferries and sailboat charter companies, we ensured the persons most likely to move iguanas were informed.
Nest location and protection / release of headstarted iguanas. A total of four nests were identified in Windlass Bight, the Faulkner site, and Bones Bight. The perimeter of each nest was fenced off with metal flashing to facilitate the collection of hatchlings upon emergence. The first nest hatched on 25 September and the last one hatched 31 October. A total of 23 hatchlings were brought into the headstart facility this year.
In October 2016, five animals were selected for release. The selected animals were released in Bones Bight as part of a publicized public release involving school children from the Claudia Creque Education Centre (grades 5–12). Researcher’s work helped the headstart facility release a maximum number of animals by collecting hatchlings, providing husbandry training, monitoring health, and conducting the releases of iguanas back to the wild. To date, the program has released 211 animals, representing at least a 52% increase in population if the 1997 estimated population of 200–400 is considered.
Camera trapping program. K. Bradley conducted three distinct types of camera surveys: burrow/retreat surveys, nesting/hatching surveys, and systematic grid surveys. The camera units were programmed to take photographs 24 hours-a-day. Camera surveys were conducted in Windlass Bight, the Faulkner site, Low Cay, Bumper Well Cay, and at all identified nests. An additional camera survey was conducted on Fallen Jerusalem Island to determine the presence/absence of invasive mammal predators.
Research time spent on the ground allowed examiners to monitor the success of repatriated iguanas and to accurately track trends in the wild population for both iguanas and invasive species. The long-term camera trapping program has documented distribution, population size, demography, and ecology of the wild/repatriated iguanas and invasive species. Systematic grid surveys enabled continuous monitoring for months at a time in strategic locations. Camera surveys decrease labor and travel expenses as well as documenting behaviors that would be impossible to observe by researchers. Ultimately, detailed population data of the core iguana area will lend support to the designation of a proposed National Park.
Fifth annual Iguana Fest. This year’s Iguana Fest took place on 21 October 2016, and had a record attendance of nearly 250 people. Students and parents played numerous iguana ecology games that engaged participants by creating a very hands-on learning experience. Participants learned about the ecosystems of Anegada, the role of iguanas in these ecosystems, the threats to the iguana’s survival, and what they can do to help save iguanas. Attendees received an official festival t-shirt promoting the Anegada Iguana. A large school group (70 students plus parent chaperones) from Virgin Gorda attended the event and participated in the annual iguana art contest for the first time.
The Iguana Festival increases local awareness and ownership by highlighting local ecological processes, the pressures threating these processes, and the connections between the island’s ecosystems, the local economy, and jobs. It also strengthens relationships between researchers, residents, NPTVI, and local business owners. The festival t-shirts also help keep the program visible year-round and create opportunities for conversations between researchers and residents.
Captive facility improvements. The existing eight information panels installed at the headstart facility were faded due to the high UV exposure on island, and some of the information needed updating (for example, the number of animals released). The graphics have been updated with current information and K. Bradley will install the new graphics on the existing sign structure this winter.
In 2015, with funding from the Disney Conservation Fund, the IIF, and the FWZ, the program purchased and installed 54 individual wire cages to use specifically for new hatchlings. These cages enabled the facility to house all newly collected hatchlings singularly. This was needed because the harsh elements in Anegada had degraded all of the pre-existing wooden cages which no longer securely held animals.
In July 2016, two FWZ staff traveled to Anegada and refurbished all the 44 individual wooden cages and the six large walk-in cages. This work resulted in a total of 104 secure and functioning cages at the headstart facility and has created a three-tier system for animals to be moved through as they grow to release size (20 cm SVL, 400 grams). Now each animal can be housed separately during the sensitive first two years growth period. This helps ensure the greatest growth rates and that the highest numbers of individuals are released in the shortest time possible.
Field vehicle maintenance. The FWZ donated a used KIA Sportage to be used as the project’s field vehicle. IIF funds were used to pay fees for inspection, registration, and insurance. By maintaining a dedicated field car, the program saves over $4,000 USD that would be needed to rent a field car. The car has a large picture of an iguana on both sides which creates opportunities for researchers to speak with international tourists about the Anegada conservation program.
Future. Anegada is home to at least five very rare Virgin Island- or Anegada-endemic plant species. As a seed disperser, the iguana could have enormous impacts on plant populations and community compositions. The FWZ and Royal Botanic Gardens Kew have been investigating the relationship between the iguana and the plant species that make up its habitat, with particular focus on threatened plant species like Varronia rupicola and the cactus Letocereus quadricostatus. Researchers are investigating the effects of saurochory (seed dispersal by reptiles) on Anegada’s plant community through seed gut-passage and seed germination studies. In addition, field observations demonstrate that where iguanas are present there are also high densities of rare plants. We hope to determine if high densities of specific rare plants are predictive of iguana presence in previously unstudied areas.
The long-term survival of this species will ultimately depend on the attitudes and actions of local Anegada residents. Specifically, there needs to be a major shift toward broadening the overall conservation plan from strictly headstarting on Anegada to a meta-population approach. Public education and outreach activities will be more important than ever to ensure we continue to increase the probability of the iguana’s survival long-term.