The West Indian rock iguanas, Cyclura spp., are a group of large, ground dwelling, herbivorous lizards that inhabit Caribbean islands throughout the Greater Antilles and the Bahamas. There are eight species with a total of 16 recognized taxa, including subspecies. Rock iguanas inhabit fragile ecosystems and most have suffered greatly over the years because of man's activities and introduced animals. All 16 taxa are currently protected under Appendix I of the Convention on International Trade in Endangered Species (CITES); three are listed as endangered by the U.S. Fish and Wildlife Service and the rest are listed as threatened. A more accurate assessment of the state of the iguanas is their classification under the new International Union for the Conservation of Nature (IUCN) categories; IUCN has recently classified all but four taxa as either critical or endangered. Today, West Indian rock iguanas are recognized as the world's most endangered group of lizards, with several species verging on extinction.
Zoos have long been concerned with the plight of these impressive dinosaur-like lizards. However, only recently has a coordinated effort been made to protect rock iguanas. At the inaugural meeting of the American Zoo and Aquarium Association's (AZA) Lizard Advisory Group (LAG) in 1990, Cyclura spp. were designated as their highest conservation priority. Zoos have since played key roles and provided strong leadership for several landmark events, described below. These events, plus the tremendous efforts that have gone into forging in situ partnerships to aid in the recovery of two critically endangered rock iguanas, have recently culminated in the formation of the AZA's first lizard Species Survival Plan (SSP) for the West Indian Rock iguanas.
This SSP concentrates on two of the most critically endangered lizards in the world, the Grand Cayman iguana (Cyclura nubila lewisi) and the Jamaican iguana (C. collei). Though the Rock Iguana SSP will be concerned with managing captive populations of these two threatened lizards as a hedge against extinction, the primary focus will be to utilize these zoo-based programs to generate support for in situ conservation and recovery programs.
The Jamaican iguana has a remarkable story which has been highly publicized in recent years. Feared extinct for nearly half a century, this iguana was rediscovered in 1990 when a pig hunter's dog captured an adult specimen in a rugged region of southeastern Jamaica, known as Hellshire Hills. Listed as critical by the IUCN, and regarded as possibly the world's most endangered lizard, the Jamaican iguana survives as a remnant population, estimated at between 50 and 200 individuals. This population remains intact primarily because of the remoteness and inaccessibility of the harsh, dry ecosystem in which it lives.
Fortunately, two active nesting sites were discovered and hatchlings have been collected annually, since 1991, for head-starting at the Hope Zoo in Kingston. Threats to the iguana's survival include predation of nesting females by hunter's dogs and habitat disturbance by charcoal burners. The single most important factor in suppressing growth of this population, however, is the introduced Indian mongoose (Herpestes auropunctatus). Mongoose predation, primarily on juvenile iguanas, results in low recruitment rates, which leads to an aging population. A Population and Habitat Viability Assessment workshop in Kingston, in 1993, focused international attention on the plight of the Jamaican iguana. Workshop results suggested that if this trend was not reversed extinction of this small population was likely.
More than ten U.S. zoos have supported the Jamaican iguana conservation and recovery program, channeling more than $30,000 in funding through the LAG since 1992. Conservation efforts have focused primarily on field research undertaken by the Jamaican Iguana Conservation and Research Group in Hellshire Hills. Conservation efforts include protecting nesting sites, working to deter hunters and charcoal burners from the core iguana area and, more recently, controlling predators and radio-tracking released iguanas. A new iguana management/head-start facility was constructed in 1994 at the Hope Zoo with funds raised through the Fort Worth Zoo. The facility now supports a population of more than 100 iguanas. Additional funds to support field research have come from the Zoological Society of San Diego and Walt Disney World Company, through AZA. The Indianapolis Zoo, which has provided consistent support to the program since its inception, maintains the Cyclura spp. studbook, a genealogical record for the captive population.
In order to guard against catastrophic loss of this large captive group in Jamaica and to avoid an "all eggs in one basket" scenario, 12 captive-raised iguanas were imported to the United States in 1994 to form the nucleus of a satellite population outside of Jamaica. These were selected from the six wild clutches available from 1991 to 1992. An additional 12 were imported in 1996, chosen based on DNA analysis, which identified new genotypes not represented in the 1994 importation. A solid founding nucleus of 24 young Jamaican iguanas is now distributed among six U.S., zoos providing ample genetic material from which to manage a healthy captive population. Reproduction is expected soon and the LAG's goal is to expand this captive nucleus to 200 individuals. Expansion, however, will require the commitment of more than just the handful of zoos now devoting resources to rock iguanas. Off-site breeding facilities being developed by a growing number of zoos can ultimately offer the space and conditions needed to manage these iguanas long-term. The challenge will be to bring these facilities into the Rock Iguana SSP.
The Grand Cayman (GC), or blue, iguana is endemic to Grand Cayman and is considered one of the world's most endangered large lizards. At the time of its description in 1940, this iguana was already considered rare and nearly extinct. Today the blue iguana clings to a precarious existence, threatened primarily by feral cat predation, and survives at low densities in fragmented habitat. It is listed as critical by the IUCN and current estimates place its total population at 100 to 200 individuals remaining in the wild.
Zoos began acquiring captive-bred specimens of GC iguanas in 1990 in order to develop a managed captive population. Unfortunately, a hybrid problem was discovered in this captive gene pool. Genetic markers for each subspecies, developed by Dr. Scott Davis at Texas A&M University, were used to identify and "weed out" hybrid iguanas, which allowed the program to start over with new stock from known, pure GC iguanas. The remaining gene pool, however, was severely limited, with only three males and one female as potential breeders-not the optimal founder number from which to build a population. Further analysis revealed that this population was descended from one pair of iguanas.
During this same time the National Trust for the Cayman Islands (NTCI) launched their own program to conserve the GC iguana. A multifaceted approach was implemented that included field research, habitat acquisition and protection, and a captive/head-start component to produce iguanas for release into depleted areas. In order to determine parentage of the small numbers of iguanas in U.S. zoos and to examine genetic diversity in the population on Grand Cayman, the Fort Worth Zoo was awarded a 1994 Institute of Museum Services grant. This project initiated the LAG's working relationship with NTCI, resulting in a strong relationship that has since channeled funding and logistical support to assist the NTCI program. For example, a new iguana management facility has been built at the Trust-managed Botanical Garden site, funded through the Milwaukee County Zoological Society.
Additional funding is being sought under the SSP for feral predator control and habitat enhancement for nesting females. An agreement was recently reached to manage both the U.S. and Grand Cayman captive populations as one entity, with bloodline exchanges occurring as needed to insure maximum genetic diversity within the total captive gene pool. This decision was based on DNA analyses and the need to optimize the genetic and reproductive potential of the limited captive numbers. Because of this program's strong in situ captive component, the GC iguana program is fast becoming a model for cooperative endangered species management.
The past five years have seen remarkable progress toward uniting and integrating the in-country recovery programs for these two critically endangered iguanas with conservation programs in U.S. zoos. Pilot releases for Grand Cayman iguanas have already demonstrated that captive-raised iguanas can survive in nature without any pre-release conditioning. The first releases of head-started Jamaican iguanas were successfully attempted in March, 1996, with more scheduled. Survival rates, assessed using radio-tracking, strongly suggest that captive-raised iguanas can indeed be used to augment and restore populations that have been extirpated in nature. It appears these iguanas have innate or instinctual survival abilities, thus making them excellent candidates for these types of recovery programs.
To fully restore these populations, however, control of feral mongoose and cat must be implemented. Most importantly, habitat preservation measures must be intensified. These activities are costly and drive the price of these recovery programs even higher. Substantial financial support from several zoos and conservation funds raised through the LAG have already assisted both these programs. Given the long-term nature of these planned reintroduction projects, the primary focus of the AZA Rock Iguana SSP will be to increase the level of support, both logistical and financial, to these programs through an aggressive and collaborative campaign involving zoos, funding agencies and universities.
The primary challenge in the next decade will be how to finance and sustain existing reintroduction programs aimed at restoring species in the wild and preventing the extinction of these iguanas. The dedication of a small group of highly motivated individuals have created an infrastructure for implementing solid conservation actions and achieved notable milestones, with minimal support, for both the Grand Cayman Iguana and the Jamaican Iguana programs. It is hoped that with the backing and guidance of the AZA Rock Iguana SSP these endangered lizards will receive the support they so urgently need.
Support for the Jamaican and Grand Cayman iguana programs has been provided by the Ministry of Agriculture/Hope Zoo and Gardens, University of the West Indies, National Wildlife Foundation, Natural Resources Conservation Authority of Jamaica, World Wildlife Fund, Environmental Foundation of Jamaica, National Trust for the Cayman Islands, Fort Worth Zoo, Zoological Society of San Diego, Jersey Wildlife Preservation Trust, Indianapolis Zoo, IUCN Conservation Breeding Specialist Group, National Zoo FONZ, Bermuda Zoo & Aquarium, Columbus Zoo, Toledo Zoo, Audubon Zoo, Gladys Porter Zoo, Denver Zoo, Sedgewick County Zoo, Central Florida Zoo, Zoological Society of Milwaukee County and the Foundation for Wildlife Conservation, John G. Shedd Aquarium, Institute of Museum Services, International Partnerships Among Museums (IPAM), and Walt Disney World Company through the AZA Conservation Excellence Campaign.
Rick Hudson is chair of the AZA Lizard Advisory Group, Species Coordinator for the Rock Iguana SSP and Assistant Curator of Reptiles at Fort Worth Zoo, Forth Worth, Texas.
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