Report submitted by Kelly A. Bradley, Fort Worth Zoo
Introduction. The Critically Endangered Anegada Iguana has been the focus of a long-term headstart and release program designed to offset high juvenile mortality resulting from the large feral cat population on Anegada. Each year iguana nests are identified during the summer nesting season and the resulting hatchlings are collected in the fall to be raised in a safe captive facility on Anegada. Once these captive iguanas reach a larger, less vulnerable size (400 gram body mass and 20 cm snot-to-vent length), they are released back into the wild. The population was estimated to be 200-300 animals prior to this conservation initiative. Encouragingly, headstarted animals exhibit high survival rates in the wild (79%) and the population has doubled to an estimated 400-500 animals. Despite these successes, the Anegada Iguana remains conservation dependent, and the current increasing population trend will cease if actions on the ground stop. Despite ongoing challenges, the 2014-2015 field season proved to be very successful and the following report details important accomplishments from the past year.
Camera Trapping Effort. The Anegada Iguana is extremely wary and very difficult to observe in the wild. In 2010, a pilot study using motion-sensitive trap cameras was conducted and proved to be successful at gathering data that would be impossible to collect otherwise (e.g., presence of iguanas outside the core iguana area, long-term survival of headstarted animals, and reproduction of headstarted animals). During the 2014-2015 field season, cameras were used at Bumper Well Cay, Windlass Bight, and Low Cay. All camera-trapping surveys collected numerous images of released and wild iguanas, feral cats, donkeys, cattle, and goats.
Bumper Well Cay – In late October at the end of the 2014 field season, camera traps were set up in a transect along the northwestern portion of the cay where iguanas are known to occur. These camera traps continuously collected images while Bradley was off island until 18 May 2015, for a total of 212 camera trapping days. The survey identified a minimum of six individuals using differences in the physical characteristics of nuchal crest, tail, and crest scales (Figures 1-6). Because of the length of this trapping event and the high number of different cameras that picked up the same animals, the results will be used to create rough home-range estimates for at least two individuals.
Prior to this camera trapping effort, very little was known about the population dynamics in this area of the island, even though it is in what is considered the core iguana area. The results from this survey shed light on the basic age and health of individuals in this area; documenting that in spite of heavy goat presence on the cay, it is a healthy group in which individuals are in close contact with each other. Based on these results, a large portion of current headstarted iguanas will be released on Bumper Well Cay in 2015.
Windlass Bight and Faulkner House – The cameras were set up in front of known iguana burrows in the Windlass Bight and Faulkner House during May and early June. Two groups of student volunteers worked on this portion of the survey, baiting cameras daily. These areas are surveyed each year in order to conduct long-term monitoring of wild and headstarted iguanas, in two of the densest areas in the core iguana area. Iguanas at both sites continued to do well and all animals appeared to have good body condition despite the severe drought in the BVI. Cameras documented both older wild animals and younger headstarted animals.
Low Cay – During July, two groups of student volunteers set the cameras in two-grid arrays at separate locations on Low Cay (largest cay in western salt ponds) for one week per grid. The traps were baited twice a day. Several wild adults were photographed, plus many headstarted animals released in 2011 and in 2014. In addition, three headstarted animals were captured and growth data were collected. Unfortunately numerous cats, goats, and cattle were also identified on this cay. Cameras will be set up on the western portion of this cay in late November and left until May 2016. This survey will cover much of the cay that has yet to be surveyed.
Anegada Iguana Festival. One of the key challenges for iguana conservation is the small, but politically vocal human population on Anegada. Unfortunately, many local residents are suspicious of government and outsider activities on Anegada. This program initiated an annual Iguana Fest in 2012 to facilitate communication with local residents and to provide a forum for education activities. The 3rd Annual Anegada Iguana Fest was held in October 2014. The festival raised public awareness of the Anegada Island ecology, with special attention paid to the Anegada Iguana. The event was held on the local British Virgin Islands (BVI) holiday, St. Ursula’s Day, when most of the BVI residents had the day off from work. The day was also a regular ferry day, allowing residents from Tortola and Virgin Gorda to attend the festival. This change in schedule resulted in a record attendance of close to 200 people. A large portion of the Spanish-speaking population from the Dominican Republic also participated, helping us reach a new demographic group on Anegada.
The event included a 1-mile and 3-mile fun run/walk for children and adults, a light breakfast for race participants, tree-planting ceremony at the headstart facility, and guided tours of the proposed protected area for iguanas and the headstart facility. A local DJ provided music for most of the festival. As in years past, there was a free hot-dog cookout and iguana cake. To commemorate the event and maintain visibility after the festival, an official Iguana Fest T-shirt was created and approximately 250 shirts were given out to festival participants. The BVI Tourist Board, plus six local businesses, sponsored the event and their logos were added to the event’s T-shirt.
The Fort Worth Zoo’s Education Department developed several high-activity games that demonstrated different aspects of the island’s ecology and local wildlife. The games illustrated 1) the flow of energy through the ecosystem; 2) how iguanas are seed dispersers and maintain a healthy forest community; 3) how invasive feral mammals negatively affect the native iguana population; and 4) how mangroves help reduce erosion. Two weeks prior to the festival, Bradley visited the local school and senior citizen center to announce an art contest to be held in conjunction with the festival. All submissions were displayed at the event; ribbons and cash awards were presented during the festival.
The 4th annual Iguana Fest took place on 19 October 2015, also on St. Ursula’s Day. The events closely followed last year’s, with new ecology games and a new official festival T-shirt. A large school group (25 students) from the neighboring island of Virgin Gorda (also part of the Ninth political district with Anegada) attended the event. The event was very successful and had a record number of children in attendance.
Release of Headstarted Iguanas. In October of 2014, 18 animals were released back to the wild. This brings the total number of released animals up the 195. Four animals were chosen for a public release with local schoolchildren in the Boneless Bight area of the core iguana area. The 14 remaining animals were released at the central portion of the main body of Low Cay. This is second release on the cay, with the first being in 2011. However the first release was on the northwestern tip of the cay.
The 13th annual release of headstarted iguanas will take place in early November 2015. An estimated 12-13 animals will be released. This will bring the total number of released headstarted iguanas to over 200. Most animals will be released on Bumper Well Cay to supplement this segment of the Anegada population surveyed in fall 2014 – spring 2015. Three to four animals will be released in a public event involving local school children in the Bones Bight area of the core iguana area.
Nesting Surveys/Hatchling Collection. Surveys were conducted in the core iguana area, Coopers Rock, and Loblolly Bay area on Anegada in July 2015. Four nests were located in the Windlass area, plus one on Middle Cay. Nesting activity was observed in Lobolly Bay, but only test digs were found before Bradley left the island. This location is a new area not previously surveyed and will be closely monitored for future nests. Nests began hatching in early October 2015. As of the end of October, 39 hatchlings have been collected. However, 19 hatchlings were used for the hatchling survival/ecology study. All study iguanas that are still alive at the end of the study in early December will be captured and transferred to the headstart facility.
New Facility Cages. The program received funding from the Disney Worldwide Conservation Fund to purchase new cages for the headstart facility. Cages were manufactured by A Thru Z Consulting (Tucson, AZ), and shipped to Anegada. IIF provided funds to facilitate the final construction of the cages and the tables on which the cages sit. The project was completed in mid-October, in time for the cages to be presented to the public at the 4th annual Iguana Fest. Fifty-two new cages were added to the facility, enabling most captive animals to be housed separately and ensuring faster growth rates. The new enclsoures directly address two problems specific to the old cages – namely the warping of wood doors and dividers between cages, both of which allowed accidental early release and animals to move between cages. For the first time, all new hatchlings will be housed individually.
Hatchling Survival/Ecology Study. Bradley is currently repeating the 2013 hatchling survival/ecology study. Nineteen hatchling iguanas from four different nests were selected to be part of the study. Each animal had a radio-transmitter attached and was released at the hatchling’s original nest site. Hatchlings will be tracked until early December, at which time all surviving hatchlings will be collected and transferred to the headstart facility on Anegada. Hatchlings are exhibiting a surprising dispersal distance, including swimming across the large western salt ponds (Red Pond and Flamingo Pond). To date, four animals have died because of snakes (Borikenophis portoricensis) and three because of cats. Animal locations are recorded daily using a Trimble GPS and ecologically-relevant information (closest plant species, height above ground, behavior, sun exposure value, etc.) is recorded for each observation.
Plans for 2016. In addition to the items listed in the 2016 IIF grant submitted for the Anegada Iguana program, we hope to complete the following items:
- K. Treiber Bradley and G. Gerber intend to submit a paper entitled “Growth and body condition index of headstarted Anegada Iguanas released to different habitat types on Anegada, British Virgin Islands” for publication by the end of the 2015.
- Iguana Fest 2016 – Next year’s festival will be the 5th year for this annual event. There are plans to increase adult participation by: 1) selling alcohol; 2) have local businesses sell food; and 3) have a large raffle for donated prizes geared towards adults.
- Work with Dr. Rob McCarthy (Tufts University veterinary school) to conduct a cat and dog spay/neuter event for Anegada residents in the summer of 2016.
- Work with Dr. Martin Hamilton (Royal Botanical Gardens, KEW, UK) to investigate the seed dispersal ecology of the Anegada Iguana. This study will include: 1) fecal analysis/dietary study; 2) gut passage time experiments; and 3) germination time experiments. It was originally planned to conduct these experiments in 2015, but Anegada was experiencing a strong drought and plant materials were not available for the gut passage or germination experiments.