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88 IGUANA  •  VOLUME 11, NUMBER 2  •  JUNE 2004 RAMER

Isla Cabritos lies in Lago Enriquillo, which is in the valley formed
by the former marine channel that separated the North and
South paleoislands that joined to form Hispaniola. Illustration by
John Binns.

A very thin Cyclura ricordii on the southern slope. Photograph by Joe Ehrenberger. 

Day’s end on Isla Cabritos. Photograph by Jennifer Niederlander.

Rhinoceros Iguana (Cyclura cornuta). Photograph by Joe Ehrenberger.



Introduction

West Indian Rock Iguanas of the genus Cyclura are the largest
living land vertebrates endemic to the Caribbean islands.

As a group, they are considered to be among the most endangered
lizards in the world. Hispaniola is the only West Indian island on

which two species of Cyclura are sympatric. Ricord’s Iguanas
(Cyclura ricordii) are critically endangered according to the
International Union for the Conservation of Nature (IUCN) Red
List. Only two or three populations, which inhabit xeric lowlands

A Survey of Ricord’s Iguanas (Cyclura ricordii)
and Rhinoceros Iguanas (Cyclura cornuta 
cornuta) in Isla Cabritos National Park,

Dominican Republic 
2003: A Preliminary Report

Jan Ramer

Indianapolis Zoo

IGUANA  •  VOLUME 11, NUMBER 2  •  JUNE 2004 89CYCLURA RICORDII

�

Isla Cabritos, terrain along the northern slope. Photograph by Kacie
Ehrenberger.

Slope approaching the central limestone plateau. Photograph by Joe
Ehrenberger. On the limestone plateau. Photograph by Joe Ehrenberger.



of the southwestern Dominican Republic, remain. Rhinoceros
Iguanas (Cyclura cornuta cornuta) have a much larger range
throughout the Dominican Republic than Ricord’s Iguanas, and
are listed as threatened on the IUCN Red List.1,3,4

Isla Cabritos National Park is situated on an island in Lago
Enriquillo, a hypersaline lake that represents a remnant of the
marine channel that once separated the North and South pale-
oislands that joined to form Hispaniola. The park is home to one
of the two or three known populations of wild Ricord’s Iguanas
in the Dominican Republic. Rhinoceros Iguanas are sympatric

with Ricord’s Iguanas throughout their range on Isla Cabritos.
The island is roughly 4 km wide and 12 km long, with dry, sandy
shores and a central plateau of fossilized coralline limestone.3

Technically, the island has been protected as a National Park
since 1974. It also is somewhat protected by virtue of the fact that
it is an island. Unfortunately, in approximately 10-year cycles, the
water level of the lake falls enough for the formation of a land
bridge on the western end of the island, allowing feral cows,
horses, donkeys, and cats to cross to the National Park. These
introduced domestic animals compete with the iguanas for
resources or, in the case of cats, prey on young iguanas.
Collectively, they constitute a direct threat to the survival of these
endangered animals. The island also is home to several native rap-
tors (e.g., American Kestrels, Burrowing Owls) that prey on
hatchling iguanas. The iguanas of Isla Cabritos were well-studied
in the 1980s by José Ottenwalder, and Sixto Incháustegui, and,
in 2000, Gloria Santana surveyed the west end of the island.

In late 2002, the IUCN Iguana Specialist Group held a
workshop in Santo Domingo, Dominican Republic to develop
a Species Recovery Plan for Ricord’s Iguanas. In fulfillment of one
the objectives of this plan, the Indianapolis Zoo (IZS) and Parque
Zoológico Nacional (ZooDom) conducted a census of Ricord’s
Iguanas and Rhinoceros Iguanas on Isla Cabritos. This prelimi-
nary report is a summary of that work.

Methods
Research groups visited Isla Cabritos on three different occasions
in 2003, corresponding roughly to Ricord’s Iguana breeding,
nesting, and hatching seasons. The first group worked on Isla
Cabritos in late April through early May 2003 and was composed
of personnel from ZooDom and IZS, along with Isla Cabritos
National Park rangers. Using Global Positioning Service units,
15 transects were set with an average length of 2 km and a sight-
line width of roughly 40 m in either direction, depending on
density of vegetation. Each transect ran the width of the island
every 500 m. Each transect was walked once, and the position of
every Ricord’s and Rhinoceros iguana was recorded, including
gender and age, if these could be determined. If species could not
be positively identified visually, the sighting was marked simply

90 IGUANA  •  VOLUME 11, NUMBER 2  •  JUNE 2004 RAMER

American Crocodile (Crocodylus acutus) along the southern shore of
Isla Cabritos. Photograph by Joe Ehrenberger.

Seeking shade after working a transect; from left to right: Francisco
Alberto Paredes, Leandro DelaCruz, Kacie Ehrenberger. Photograph
by Joe Ehrenberger.

The “landbridge” exposed during periods of low water level connects
the west end of Isla Cabritos to the main island shore. Photograph by
Joe Ehrenberger.

Feral donkeys along the southern shore. Photograph by Joe Ehrenberger.



IGUANA  •  VOLUME 11, NUMBER 2  •  JUNE 2004 91CYCLURA RICORDII

Isla Cabritos showing the transects marked during the iguana surveys (bottom) and locations where iguanas were sighted during the June survey (top). 



as “iguana.” Iguana dens and scat also were recorded. Three adult
Ricord’s Iguanas were captured, affixed with microchips, given
complete physical examinations, and released. All domestic ani-
mals (burros, cattle, horses, and cats) were recorded, as were any
other significant observations.

The second group consisted of personnel from ZooDom,
IZS, and the Fort Worth Zoo, and Isla Cabritos National Park

rangers. This group worked on Isla Cabritos in late June through
early July 2004. This group set five additional transects and
walked each transect once using the methods established in April.
A horticulturist from the Indianapolis Zoo began cataloging
plant species during this visit.

The last group worked on Isla Cabritos just after the hatch-
ing season, in late September 2004. Zoodom and IZS personnel,
along with Isla Cabritos National Park rangers walked each tran-
sect using the same methods as the first two groups. Unsuccessful
attempts were made at capturing hatchling Ricord’s Iguanas for
collection of biological data. Three adult Ricord’s Iguanas were
captured, affixed with microchips, and released.

Results
In April, researchers sighted a total of 31 Ricord’s Iguanas, includ-
ing 11 males, 12 females, five adults of unknown gender, and
three juveniles of unknown gender. In contrast, only seven
Rhinoceros Iguanas were seen, including one male, five females,
and one adult of unknown gender. Rhinoceros Iguanas were seen
on transects nearest the tourist trail and at the far eastern end of
the island, but the majority of sightings on the interior of the
island were Ricord’s Iguanas. Six donkeys and one horse were
sighted while walking transects in April, but herds of up to 12
horses were noted at other times. A total of 32 active dens were
found while walking transects; one known to be inhabited by a
Rhinoceros Iguana and five known to be inhabited by Ricord’s
Iguanas. These dens were found primarily on either slope of the
island throughout its length. Few den or iguana sightings
occurred on the rocky plateau.

92 IGUANA  •  VOLUME 11, NUMBER 2  •  JUNE 2004 RAMER

Vegetation around the opening of a Cyclura ricordii burrow.
Photograph by Joe Ehrenberger.

Typical Cyclura cornuta cornuta burrow, large and in an open area.
Photograph by Joe Ehrenberger.

A common cactus (Harrisia nashii) bears yellow fruits eaten by igua-
nas. Photograph by Kacie Ehrenberger.

Typical Cyclura ricordii burrow in a dense cactus stand. Photograph by
Joe Ehrenberger.



IGUANA  •  VOLUME 11, NUMBER 2  •  JUNE 2004 93CYCLURA RICORDII

In June, the team arrived just after the nesting season
because the rains came early and nesting had occurred earlier
than expected. A total of 16 Ricord’s Iguanas (10.6) and three
Rhinoceros Iguanas (2.1) were sighted on transects. The pattern
of sightings was consistent with the April trip. Many active dens
were noted, including those of 34 Rhinoceros Iguanas and 39
Ricord’s Iguanas. Dens were designated as being inhabited by
Ricord’s or Rhinoceros Iguanas either by sighting an animal
entering the den, or by the shape and location of the den.
Ricord’s Iguana dens tend to have openings with a greater soil
spread of a finer size and are commonly associated with areas of
thorny vegetation consisting mainly of Cylindropuntia caribaea.
In contrast, Rhinoceros Iguana dens often have openings with
larger size soil particles that fan out less widely and tend to be in
more open areas. Ernst Rupp reported in his survey of the
Barahona Peninsula (see IGUANA 11(1): 8–14) that Ricord’s
Iguana tail drags are much smoother in fine sand, and therefore
notably different than Rhinoceros Iguana tail drags.2 However,
this was not the case on Isla Cabritos, possibly due to differences
in substrate consistency. One nest was seen, but the species was
unknown. Far more domestic animals were seen in June; these
included eight donkeys, four cows, two horses, and two sets of
cat tracks.

Plant communities found on the island during the June trip
varied according to the different microclimates and substrates.
Certain plants such as Calotropis procera were widespread, but
tended to be most common in the sandier soils found near the
beaches. The limestone plateau supported less plant life.
However, Melocactus sp., the fruits of which are known to be
eaten by iguanas, was only found growing in the limestone and
nowhere else on the island. Many other cacti, including
Cylindropuntia caribaea, Harrisia nashii, and Pilosocereus poly-
gonus, were fairly widespread, although they were absent from the
limestone plateau. The most prevalent cactus found near the
limestone was Consolea moniliformis. Scrubby vegetation, such as
Guiacum officinale, Guapira brevipetiolata, Prosopsis sp., and
Ziziphus rignonii, was found throughout the island as well, but
seemed to be in higher concentrations near the limestone out-
croppings. 

Fewer iguanas were seen in September, but the areas in
which they were seen corresponded well to the first two trips. Ten
Ricord’s Iguanas (3.5.2) were seen and only two female
Rhinoceros Iguanas were seen on transects. Recent scat and tail
drags were evident in many areas. Forty-two active Ricord’s
Iguana dens and 27 active Rhinoceros Iguana dens were noted.
Donkeys (4) and cows (1) were seen while walking transects.
Horses, cows, and donkeys also were observed around camp, and
larger numbers of these animals were reported by Park rangers.
Two hatchling Ricord’s Iguanas were seen on this trip, but could
not be caught for measuring and microchip placement.

Discussion and Recommendations
Using the April data of 31 Ricord’s iguana sightings on the 15
transects walked, crude population estimates are calculated at 0.13
Ricord’s iguanas and 0.03 Rhinoceros iguanas per hectare sur-
veyed. Curiously, Rhinoceros Iguanas were found only along the
edges of the island on the central and eastern end, and near the

tourist trail on the west end of the island. The sighting of 43 active
Ricord’s Iguana dens on the 20 transects walked in June also is
encouraging, and, if one assumes one adult animal/den, a crude
estimate of population density remains around 0.13 Ricord’s
Iguanas per hectare surveyed. These estimates are considerably
lower than densities calculated by Incháustegui, who reported 8
iguanas/hectare on Isla Cabritos in 1985.5 In her survey of the
west end of Isla Cabritos in 2000, Gloria Santana estimated the
density of Ricord’s Iguanas to be 1.8 individuals/hectare and
Rhinoceros Iguanas to be 1.75 individuals/hectare.5 Population
densities quite possibly are lower now than in 2000, but another
explanation is that the current survey covered the whole island,
including habitat that is not necessarily suitable iguana habitat.
The nearly 1:1 ratio of Ricord’s:Rhinoceros iguanas in Santana’s
work is consistent with current observations of larger numbers of
Rhinoceros Iguanas near the tourist trail and west end than in the
central region and the eastern end of the island.

The only other Ricord’s Iguana habitat that has been actively
surveyed on Hispaniola in recent years is the work of Ernst Rupp
et al. in 2003. He estimated roughly 32 iguanas per hectare in
the Los Alivares area of Pedernales Province based on number of
active dens sited along one transect.2 While these data appear to
suggest that populations on Isla Cabritos may be very depleted,
the estimates in Los Alivares were based on work in areas known
to support iguanas.  Also, population estimates based on the very
low number of sightings made in the current survey are extremely
crude and are almost guaranteed to provide low estimates. More
detailed analyses of the data are in progress, and continued
annual surveys and more detailed behavioral observations are
needed to better understand the biology of these animals.

The large number of domestic livestock noted on all three
trips is troublesome. Not only do they directly compete with igua-
nas for forage, they also cave in dens and trample nests. The water
level was considerably lower in September than in April, making
the land bridge very wide and easily crossed by livestock and pred-
ators. Ideally, the land bridge should be fenced, and livestock
should be driven off the island. Very few signs of feral cats were
noted during this survey; however, no attempts were made to sur-
vey for cats at dusk or night. The fact that cat sign was seen at all
indicates that a program to reduce the number of cats is needed,
and this could include night trapping or shooting of animals.

These data will be presented at a meeting of the Ricord’s
Iguana Recovery Group in Santo Domingo this summer, and,
based on this work and the work of Rupp et al., the nature of
future conservation efforts for Ricord’s Iguanas will be deter-
mined at that meeting. The Isla Cabritos population remains very
important to the conservation of this critically endangered
species, and further work there could include the following:
• Continued annual surveys (easily accomplished by park

rangers if proper equipment and training were available).
• Additional transponder and telemetry studies (also by park

rangers in many instances).
• Perform mark/recapture studies to more clearly establish pop-

ulation densities in different parts of the island.
• Track hatchlings (longer-term studies to identify relationships

between animals of all ages and vegetation and substrate pat-
terns on the island).



Participants
APRIL: Roberto Maria, Senior Veterinarian, ZooDom; Melvin
D’Oleo, Isla Cabritos National Park Ranger; Adriano Menier,
Senior Keeper, ZooDom; Jan Ramer, Associate Veterinarian,
Indianapolis Zoo;  John Wyatt, Deserts Senior Keeper,
Indianapolis Zoo.

JUNE: Francisco Alberto Paredes, Senior Keeper, ZooDom;
Jennifer Niederlander, Veterinary Technician, Indianapolis Zoo;
Leandro DelaCruz, Veterinary Student, ZooDom; Lori Johnson-
Roedell Curator of Horticulture, Indianapolis Zoo; Meg
Bommarito, Conservation Department, Fort Worth Zoo; Melvin
D’Oleo, Isla Cabritos National Park Ranger; Adriano Menier,

94 IGUANA  •  VOLUME 11, NUMBER 2  •  JUNE 2004 RAMER

Vegetation of Isla Cabritos: 1–3. Caloptropis procera leaves, fruits, and flowers, all of which are eaten by iguanas; 4–5. Consolea moniliformis stand
and close-up of the trunk; 6–7. Cylindropuntia caribaea forms impenetrable forests; 8. Guaiacum officinale bark; 9. Harrisia nashii grow very large
and often provide shelter for C. ricordii burrows; 10. Melocactus sp. are scattered across most areas of the island; 11. C. ricordii burrows are fre-
quently associated with Pilosocereus polygonus, another abundant cactus; 12. Ziziphus rignonii seeds germinate more rapidly after passing through
the digestive tracts of iguanas. Photographs by Lori Johnson-Roedell.

1

2

5

6

9

10

3

4

7

8

11

12



IGUANA  •  VOLUME 11, NUMBER 2  •  JUNE 2004 95CYCLURA RICORDII

Senior Keeper, ZooDom; Richard Searcy, Deserts Keeper,
Indianapolis Zoo.
SEPTEMBER: Francisco Alberto Paredes, Senior Keeper,
ZooDom; Leandro DelaCruz, veterinary student, ZooDom; Joe
Ehrenberger, Deserts Keeper, Indianapolis Zoo; Kacie
Ehrenberger, Wildlife Biologist and Indianapolis Zoo Volunteer;
Emily Hansen, Educator, Indianapolis Zoo; Melvin D’Oleo, Isla
Cabritos National Park Ranger; Adriano Menier, Senior Keeper,
ZooDom; Jan Ramer, Associate Veterinarian, Indianapolis Zoo,
Alice Wright, veterinary student, Edinburgh, Scotland. 

Acknowledgements
This work was supported by the Indianapolis Zoo Conservation
and Research Department, the Miami Metrozoo, Cleveland Zoo,
Parque Zoologico Nacional (ZooDom), and the American
Association of Zoo Keepers, Indianapolis Zoo Chapter. Many
thanks to Richard Searcy for compiling GPS data and making
maps. John Binns can never be thanked enough for his many
contributions to iguana conservation, this project being no excep-

tion; thank you, John. And finally thanks go to all of the survey
participants for their hard work under considerably less than
comfortable conditions. 

References
1. Alberts, A.C., R.L. Carter, W.K. Hayse, and E.P. Martins (eds.). 2004.

Iguanas: Biology and Conservation. University of California Press, Berkeley.

2. Arias, Y., S.J. Incháustegui, and E. Rupp. 2004. Cyclura ricordii on the
Barahona Peninsula: A Preliminary Report. Iguana 11: 9–14.

3. Ottenwalder, J.A. 1999. Ricord’s Iguana, Cyclura ricordi, pp. 51–55. In: A.
Alberts (ed.), West Indian Iguanas: Status Survey and Conservation Action
Plan. IUCN/SSC West Indian Iguana Specialist Group. IUCN, Gland,
Switzerland and Cambridge, UK.

4. Powell, R., J.A. Ottenwalder, and S.J. Incháustegui. 1999. The
Hispaniolan herpetofauna: Diversity, endemism, and historical perspectives,
with comments on Navassa Island, pp. 93–168. In: B.I. Crother (ed.),
Caribbean Amphibians and Reptiles. Academic Press, San Diego, California.

5. Santana Zorrilla, G.M. 2001. Introduccion al Estudio de las Problaciones de
Cyclura en la Isla Cabritos, Lago Enriquillo, República Dominicana. Thesis
para optar por el titulo de licenciatura en biologia, Universidad Autonoma
de Santo Domingo, Facultad de Ciencias.

The September surveying team (from left to right): Melvin D’Oleo,
the author, Alice Wright, Adriano Menier, Francisco Alberto Paredes,
Joe Ehrenberger, Leandro DelaCruz, Kacie Ehrenberger, and Emily
Hansen.

Male Ricord's Iguana on Isla Cabritos (November 2002). Photograph by John Binns.

Seeking shade after working a transect; from left to right: Leandro
DelaCruz, Emily Hanson, Kacie Ehrenberger, Jan Ramer, Alice
Wright. Photograph by Joe Ehrenberger.


