Ricord's iguana
Cyclura ricordi

By Jose Ottenwalder

Description

Ricord's iguana is a large (SVL to 495mm in males, 430mm in females) iguana that can be readily distinguished by greatly enlarged and spinose scales at each caudal verticil in both adults and juveniles. Color patterns show little individual or ontogenetic variation, consisting of five to six bold pale gray chevrons alternating with dark gray to black chevrons, of which five continue as bold but narrow lines diagonally onto the venter. In adults, the dark chevrons are less contrasting than in juveniles.

Distribution

Ricord's iguana is known only from southwestern Dominican Republic, where it is restricted to the arid Valle de Neiba and the most xeric portion of the Peninsula de Barahona coastal lowlands (Fig. 8). The two populations are separated by the mesic Sierra de Bahoruco (Massif de la Selle in Haiti), with three peaks exceeding 2000m that form an extensive ecological barrier. Past drier Pleistocene climates may have allowed genetic exchange between the two subpopulations. Throughout their range, Ricord's iguanas are sympatric with rhinoceros iguanas.

The Neiba Valley population includes Isla Cabritos, a 12 by 2km island in Lago Enriquillo, a hypersaline lake that undergoes extreme reductions every 15-30 years due to severe droughts and high evapotranspiration. In the past, this has caused the island to become connected with the southwestern lakeshore, producing a peninsular effect and allowing two-way population exchange of Ricord's iguana and rhinoceros iguanas inhabiting the lake periphery. Return to previous insular conditions occurs during years of unusually heavy rainfall. The 1979-1980 cyclic episode resulted in lake levels rising more than 3m. Following a two-year period of increased drought and reduced rainfall, as of March, 1997, Isla Cabritos again became connected with the mainland, at the southwestern portion of the lake's shoreline near Jimani. J. Ottenwalder suspects that one-way migration from Isla Cabritos to the lake's south shore allows for dispersal between cyclic peninsular events. Over-water dispersal of iguanas could be aided by water surface currents generated by strong daily winds from Neiba Bay through the Neiba Valley, together with increased buoyancy provided by hypersaline water. Both Ricord's iguanas and rhinoceros iguanas will float and swim in fresh water (J. Ottenwalder, personal observation).

In the Barahona Peninsula range, the distribution of Ricord's iguana has yet to be accurately established. Areas of occupancy include lowlands to the north, northeast, and east of the Cabo Rojo region, below the lower foothills of Sierra de Bahoruco, and on the western side of the Parque Nacional Jaragua. The oldest known occurrence inside the park is the northwestern corner at Tru Nicolá, although the precise extent to which the species distribution continues east and south is insufficiently known. However, park wardens have recently observed Ricord's iguanas in the eastern and southwestern portions of the park, including the Oviedo Lagoon, where the species inhabits limestone areas of the shoreline and several small cays inside the lagoon.

The presence of Ricord's iguanas in the Haitian extension of the Neiba Valley plain has been presumed (Schwartz and Carey 1977). However, the species has never been recorded from the Lake Etang Saumatre basin or the dry coastal fringe extending from Anse-a-Pitres to Marigot across the Dominican border at Pedernales.

Status of populations in the wild

All available data indicate that the historical range of Ricord's iguana was small and disjunct. Several factors indicate that the population is currently declining, including direct observation, reduction in the extent and quality of available habitat, and documentation of the negative effects of introduced species. Researchers and local inhabitants agree that until the mid-1970s, population densities of mature individuals were much higher than they are at present. Lacking more accurate data, a current population estimate of 2,000 to 4,000 is probably conservative but fair.

Ecology and natural history

Compared to rhinoceros iguanas, Ricord's iguanas are quite specialized. Several key environmental factors, including soil depth and texture, landform, bedrock parental material, and climate seem to determine their presence. Ricord's iguanas inhabit the most arid regions of the Dominican Republic, where the climate is highly seasonal. Representative localities include Duvergé (annual rainfall 470.6[178.4-812.8]mm, 46.6 days/year; 28.8[23.1-33.0]°C) and Pedernales (annual rainfall 633.3[160.2-1922.8]mm, 34.7 days/year; 27.9[21.5-34.1]°C). Annual precipitation is distributed in two rainy periods, May-June and September-October, while December-March is exceedingly dry.

Ricord's iguanas are strongly associated with thorn scrub woodlands, particularly with the thorn scrub-dry forest ecotone. Typical habitat can be found north of Cabo Rojo inside the fork of the Oviedo-Pedernales and Cabo Rojo-Acetillar bauxite mine roads. The topography of the area consists of a series of broad, flat plains punctuated by rocky steps and marine terraces with very fine soil over exposed dogtooth limestone. The plant community is disturbed and not very diverse, consisting of only about 35 species of tracheophytes (18% endemic) (Fisher-Meerow 1983; Fisher-Meerow and Judd 1989). Members of the Cactaceae, Fabaceae, and Euphorbiaceae are common. A single species, Acacia macracantha, comprises 50% of the cover. Other common trees are Capparis ferruginea, Guaiacum officinale, Haitiella ekmanii, Metopium brownei, Opuntia moniliformis, and Phyllostylon brasiliense. Common shrubs include Croton origanifolius, Croton discolor, and Lipia alba. Among the succulents, Agave brevipetala, Cephalocereus polygonus, Harrisia nashii, Melocactus communis, Cylindropuntia caribea, and Opuntia dillenii predominate. Trees and shrubs are widely spaced, without forming a closed canopy. Further north, only rhinoceros iguanas are present at a second, higher elevation site, with similar temperature but greater rainfall. This area consists of a marginal subtropical dry forest community on eroded dogtooth limestone and gently sloping terrain with occasional step cliffs and terraces. Here, plant diversity is higher (45 species, 9% endemic), and Malvaceae, Euphorbiaceae, and Fabaceae are the most abundant families in number of species and individuals. Capparis ferruginea, Zizyphus rignoni, Cameraria angustifolia, Cordia buchii, and Plumeria obtusa are common, although some species are restricted to limestone outcrops. Shrubs include Abutilon abutiloides, Comocladia dodonea, Croton ciliato-glandulifera, Cryptorhyza haitiensis, Guaiacum sanctum, Hybanthus havanensis, Lantana camara, and Turnera diffusa. Vines are very common, as is the herb Callisia repens. Plants with spines are nearly absent from less disturbed areas, while vegetation approaches thorn woodland in the most disturbed areas. These are generally dominated by open-canopy legumes, including Acacia macracantha, Prosopis juliflora, and Senna atomaria. Acacia-dominated areas probably represent secondary reductions of more diverse past communities. In the the transition zone between these two sites, both iguana species are present, sharing the more diverse edge habitat.

On Cabritos Island, where Ricord's iguanas have historically outnumbered rhinoceros iguanas based on frequency of sightings by visiting researchers, the plant community is a succulent-dominated 5-6m dry forest on white sandy soil with low topography. Ricord's iguanas occur on north and south gentle slopes as well as on the central plateau, where soil conditions are favorable for their extensive burrows. Among other shrubs, Cylindropuntia caribea is common. On the south mainland shores, Ricord's iguanas outnumber rhinoceros iguanas by a factor of nine in the flatlands surrounding Laguna del Medio near El Limon, considered the driest area in the country. The soil is very fine, porous, and from dark to whitish gray color, without rock exposure. Savanna vegetation cover is about 25%, dominated by Jacquinia (two species), Piscidia ekmanii, Maytenus buxifolia, and the less common Prosopis juliflora; shrubs include Mimosa sp., Pictelia spinifolia, Crossopetalum decussatum, Turnera diffusa, Croton discolor, Malpighia sp., and Lantana decussatum; grasses include Portulaca sp., Evolvulus sericeus, Stylosanthes hamata, and members of Poaceae (DVS/SEA 1990). Ricord's iguanas feed on a wide variety of plants and plant parts, depending on local availability, including Consolea, Opuntia, Croton, Prosopis, Melocactus, Cordia, and Guaiacum. Insects and crustaceans are also taken opportunistically.

Seemingly optimal habitats are characterized by alluvial powdery-clay soils bordered by marine sediments and low forested hills with high plant diversity. Flat topography, low precipitation, and local soil conditions (e.g. fine texture, slow permeability, low flooding risk, good drainage) allow for low erosion rates and maximum soil stability. While rhinoceros iguanas make extensive use of limestone crevices in addition to soil burrows, Ricord's iguanas prefer to dig soil burrows which they continue to expand over time. Hollow tree trunks and rock cavities are also used for retreats when soil is unavailable. Retreat entrances are generally dug under dense thorny vegetation, shrubs, stumps, or exposed rocks.

Nesting sites are separate from retreats, in fine sandy soils. Egg laying is highly synchronized with the first rainy period (May-June). Females lay 2-18 eggs per clutch (mean 11.1 ± 4.2). Egg chamber depth is about 40cm, with a stable temperature of 30-31°C. Incubation lasts 95-100 days, and hatching is synchronized with the second rainy season (September-October). Average SVL and mass of hatchlings is 87.4mm and 30g. Females reach sexual maturity at about 2-3 years of age. In captivity, first time clutches are usually very small (2-4) and often infertile. The social behavior of Ricord's iguana generally resembles that of other rock iguanas, although wild males defend females much more aggressively in captivity than do wild male rhinoceros iguanas maintained at lower densities in comparable enclosures. Although of major research interest and significant conservation importance, little is known of interspecific interactions between Ricord's and rhinoceros iguanas.

Habitat

The total range of Ricord's iguana in the Dominican Republic is under 100km2, and less than 60% of the historical range is occupied, most of it showing various levels of disturbance. Suitable habitat has been severely reduced by clearing, fragmentation, and transformation, including some of the oldest and best known iguana sites. The area along the south shore of Lake Enriquillo between Duvergé-Las Baitoas and El Limon has suffered considerable habitat loss as a result of agricultural development, free-ranging livestock, charcoal production, fuelwood extraction, and drainage of a lagoon and small seasonal wetlands. The Isla Cabritos range, which used to be intensively exploited for hardwood cutting, charcoal, and livestock grazing (up to 500 goats, 200 burros, and some cattle), has experienced extensive natural regeneration during the past 15 years. Since 1992, protective management has improved, and present conditions are stable.

The distribution of Ricord's iguana in the Barahona Peninsula range is insufficiently known due to the impenetrable, dense nature of the vast dry forest that extents inside Parque Nacional Jaragua. Confirmed areas of occurrence include relatively small patches of lowland thorn scrub and thorn scrub-dry forest ecotone in the Cabo Rojo region north of the Oviedo-Pedernales road, lowlands 150m to the north and northeast of Cabo Rojo at the base of lower foothills of Sierra de Bahoruco, and on the western side of the park. Inside the park boundaries, Ricord's iguanas are best documented from the northwestern corner and from the Oviedo Lagoon area. As penetration of the forest along this section is extremely difficult due to thick thorny forest and uneven dogtooth limestone terrain, the extent to which the species range continues to the east and south is still uncertain. Outside the park, iguana habitats are being reduced by conversion to farmlands, limestone mining, charcoal production, fuelwood collection, hardwoods extraction, and grazing livestock. Habitat protection inside the park has improved, although similar human impacts on forest communities supporting iguanas still occur inside and along buffer zones areas.

Threats

The major threats to Ricord's iguanas are from human activities resulting in habitat reduction and degradation (clearing of vegetation for agricultural use, charcoal production, harvesting of fuelwood and hardwoods, overbrowsing by free-ranging livestock, mining of limestone, illegal collection of live cacti for local and international trade), in combination with local subsistence hunting for food and predation from introduced carnivores (dogs, cats, and mongooses). Competition from mammalian herbivores probably also occurs. Hunting of Ricord's iguanas for food and trade has increased gradually since the mid 1970s, both for local consumption as well as at a few oriental restaurants in Santo Domingo where iguanas were offered as a specialty dish. In the past, some hunters used to set up to 100 snare traps per day at the entrance of retreats, with 30-50% trapping success. Although current populations no longer support the numbers harvested 15 years ago, iguanas continue to be captured opportunistically in all areas with remaining populations, except on Isla Cabritos where law enforcement is presently effective.

Current conservation programs

Aside from occasional smuggling of animals across the Haitian border, compliance with international CITES trade regulations is effective. Enforcement of national protective legislation in the Dominican Republic has improved during the past few years, but effective control is adversely influenced by a number of factors. Clearing of natural habitat for development is not being prevented nor regulated and illegal hunting for food and the local pet market continues.

Ricord's iguana is partially protected in two areas. In the Neiba Valley, about 60% of the area supporting iguanas, including Isla Cabritos and a section of the south shore of Lake Enriquillo, is protected within the recently created Lago Enriquillo National Park. The Isla Cabritos population has been protected within Isla Cabritos National Park since 1974.

In the Barahona Peninsula range, two protected areas, Parque Nacional Jaragua and the Acetillar Scenic Reserve, cover most of the remaining distribution of the species to the north and east of Cabo Rojo. Ricord's iguanas are only known from the park's western boundary, where conflicts with limestone mining concessions on both sides of the park border continue to be unresolved. Until now, no formal management has been established in the Acetillar reserve, and the habitat is impacted by a variety of activities.

As of November, 1995, the total captive population of Ricord's iguana was 5.9 individuals in two collections (Indianapolis Zoo and one private collection; B. Christie, personal communication). Successful captive breeding has been achieved in both, but survivorship of young has been low (J. Ottenwalder and B. Christie, unpublished data). The only other significant captive breeding program was developed at the Parque Zoologico Nacional (ZooDom). Although adversely affected by institutional problems, the program lasted for a number of years with comparable success. There are plans to re-establish new breeding colonies at both ZooDom and the Indianapolis Zoo, as part of a collaborative program between the two institutions. ZooDom recently completed a breeding exhibit to house a founder group once ongoing population surveys indicate it is safe to remove animals from the wild.

Critical conservation initiatives

• Effective enforcement of current regulations protecting populations.
• Strengthening of current regulations and legislation protecting iguana populations by increasing fines and designating selected areas as critical habitat whether outside or inside existing protected area boundaries.
• Development of educational awareness campaigns to promote iguana conservation, particularly to discourage subsistence hunting of iguanas for food and local trade, and habitat conversion for charcoal production.
• Development of a national conservation and recovery strategy and working group to include government agencies, non-governmental conservation organizations, and iguana researchers.
• Establishment of research, management, and monitoring programs for wild populations and critical habitats.
Involvement of local organizations and communities in any iguana conservation, education, and research activities.

Priority projects

1. Conduct status surveys of the Parque Nacional Jaragua-Cabo Rojo and Lake Enriquillo iguana populations.
2. Carry out field studies on natural history and ecology, and assessments of population trends and threats in order to develop a recovery strategy.
3. Immediately eradicate cats from Isla Cabritos.
4. Establish local and national educational programs in order to reduce current causes of mortality, raise awareness concerning threatened status, and promote support for proposals to expand boundaries of existing protected areas.
5. Re-establish a captive breeding and research program at ZooDom, while continuing to strengthen the ongoing program at the Indianapolis Zoo.

Contact persons

Jose Ottenwalder
UNDP/GEF Dominican Republic Biodiversity Project
United Nations Development Program
PO Box 1424, Mirador Sur
Santo Domingo, Dominican Republic
Tel: (809) 534-1134
Fax: (809) 530-5094
E-mail: biodiversidad@codetel.net.do

Bill Christie
Indianapolis Zoo
1200 W. Washington Street
Indianapolis, IN 46222 USA
Tel: (317) 630-5172
Fax: (317) 630-5153
E-mail: bchristi@mail.indyzoo.com

Sixto Inchaustegui and Ivon Arias
Grupo Jaragua Inc.
El Vergel 33
Santo Dominigo, Dominican Republic
Tel: (809) 472-1036
Fax: (809) 412-1667
E-mail: emys@tricom.net

Departamento de Vida Silvestre
Subsecretaria de Rescursos Naturales
Secretaria de Estado de Agricultura
Santo Domingo, Dominican Republic