






































Iguana b&w text


12 IGUANA  •  VOLUME 15, NUMBER 1  •  MARCH 2008 GOETZ

Adult Sister Isles Rock Iguana (Cyclura nubila caymanensis) in the interior shrubland of Little Cayman.



Among the world’s most endangered reptiles, West Indian
rock iguanas of the genus Cyclura have attracted consider-

able attention from the conservation community. Monitoring,
captive-breeding and reintroduction efforts, or translocation
projects have been initiated for many species. The numbers of
Cuban Rock Iguanas (C. nubila nubila) are relatively large
(Perera 2000), but monitoring the status and assessing numbers
of the subspecies, C. n. caymanensis, endemic to the islands of
Little Cayman and Cayman Brac, has been neglected. Whereas
the subspecies is listed as Critically Endangered on the IUCN
Red List (Gerber, 1996) due to the small area of occupancy and
the fact that only about 40 animals are believed to survive on
Cayman Brac (Burton, pers. comm.), surveys never have been
conducted on Little Cayman. Little Cayman is a small island

The Cayman Sister Isles Iguana Project:
Identifying the Conservation Needs of

Cyclura nubila caymanensis
Matthias Goetz

Herpetology Department, Durrell Wildlife Conservation Trust

Photographs by the author except where noted.

IGUANA  •  VOLUME 15, NUMBER 1  •  MARCH 2008 13CYCLURA NUBILA CAYMANENSIS

�

Adult male Cyclura nubila caymanensis at the west end of Little Cayman (top), and an adult female (bottom).



(28 km2) inhabited by fewer than 200 residents. Most of the
land is in private ownership, and the rate of development
increasing steadily.

In the mid-1990s, about 1,500–2,000 iguanas were thought
to live on the island, although declines were projected (Gerber
1996). What little knowledge we have concerning the popula-
tion since then, its status and current threats, is the result of irreg-
ular trips by Fred Burton, head of the Blue Iguana Recovery
Program on Grand Cayman, over the past decade and unpub-
lished research conducted by Glenn Gerber in 1993. A popula-
tion update, status assessment, and determination of the long-
term conservation needs of C .n. caymanensis are long overdue.

Aims
In 2007, in close collaboration with the Cayman Islands
Government Department of Environment and the National
Trust for the Cayman Islands, the Durrell Wildlife Conservation
Trust initiated the multiyear Cayman Sister Isles Iguana Project.
The overall goal is to provide the Caymanian Government and
Little Cayman and Cayman Brac residents with the knowledge
and tools to preserve this subspecies in the long-term.

Without any reliable and current figures on the overall pop-
ulation size and its status, the first task for field researchers was
to try to determine the existing population size, distribution, and

genetic heterozygosity. Future research will investigate aspects of
nesting ecology applicable to conservation, and identify the fac-
tors limiting distribution and density with a view towards their
amelioration.

14 IGUANA  •  VOLUME 15, NUMBER 1  •  MARCH 2008 GOETZ

The author and volunteer Adam Mitchell taking blood samples for genetic analysis from a juvenile iguana.

M
IC

H
A

EL
 V

A
LL

EE

The author measuring and flagging a sample quadrat in the shrubland
of Little Cayman.

Y
V

ES
 L

A
C

O
M

B
E



IGUANA  •  VOLUME 15, NUMBER 1  •  MARCH 2008 15CYCLURA NUBILA CAYMANENSIS

Fieldwork 2007
From the beginning of October until the end of November
2007, an estimate of the current population size was made by
plot sampling using randomly allocated 20 x 40 m quadrats, as
other methods (e.g., distance sampling) are unsuitable for
Cyclura spp. in the types of habitat present in the Cayman
Islands (Burton, pers. comm.). Each quadrat was visited on three
consecutive days to allow occupancy modeling of rock holes
(i.e., occupied retreats were counted rather than visible iguanas).
The third visit to each quadrat included a four-hour observation
period beginning at sunrise and conducted by three people and
additionally using five IRCF ID cameras (see IGUANA 14(3):
208–209).

Using this method, we visited 22 quadrats, but surprisingly
could detect only a single occupied retreat. With this very small
sample size, our population estimate is a total of 1,800 individ-
uals on Little Cayman; however, this is only reliable to an order
of magnitude.

The problem is that the method was designed for randomly
or evenly distributed populations or population patches, but, in
suitable natural habitats on the island (i.e., dry scrubland and
less dense forest — we did not include the abundant mangroves
and wetlands, as iguanas are not present in these habitats), a dis-
turbingly low number of iguanas were encountered. In fact, hik-
ing through the bush almost daily for two months to reach the
sample quadrats, we encountered or heard only another five
individuals. The statement that iguanas reach their maximum
densities in the interior shrubland (“bushland” — Brunt 1994,
in Gerber 2000) therefore cannot be confirmed.

The situation was very different along roads or in otherwise
disturbed areas, mostly around areas of human habitation. Adult
iguanas were encountered frequently along roadsides in the
south and east, and around houses in the west, giving residents
and tourists the impression of a fairly healthy population.
Disturbingly, younger age classes were very rarely seen.

This clustering of adult iguanas in disturbed areas and its
potential effects on the population, whether detrimental or ben-
eficial, will be addressed further in future field trips. Similarly,

Typical shrubland habitat in the interior of the island. Whether iguanas reach their maximum populations densities in such habitat cannot be
confirmed at this time.

“Disturbed“ habitat is not necessarily inhabited by people. A landfill
near the site of the attempted but until now abandoned new airport.
One adult pair and three hatchling iguanas have been observed at this
locality.



with appropriate survey methodologies, we will be able to obtain
more accurate data on the population sizes in clustered areas, as
well as a better understanding of the apparently very low den-
sity in undisturbed habitats.

In addition to the population study, we opportunistically
recorded GIS positions of all 90 iguanas we encountered. We
were able to catch 52 of these, which we marked with PIT-tags
and color-coded bead tags on their dorsal crests. Morphometric

data also were taken from all captured individuals and blood
samples were collected from 48 for genetic analysis, the results
of which are pending.

Glenn Gerber marked approximately 200 iguanas in his
1993 study (Gerber, pers. comm., Gerber 2000) but, as PIT tags
were not widely available at the time, no reliable long-term tag
data were available for reference purposes.

Threats
The most imminent threats to C .n. caymanensis on Little
Cayman seem to be feral cats and road mortality. During our
stay in October and November, we found three freshly killed
adult iguanas on the road, but residents advised us that many
more road deaths occur during the breeding season. This is to
be expected, as males roam more widely in search of mating
partners around May, and gravid females migrate to nesting sites
on the beaches beginning in June. Taking this into account, as
well as the fact that not all road deaths will be detected or
reported, we are estimating that the population might lose
40–50 breeding adults per year as a consequence of road mor-
tality. To establish more accurate numbers and involve the entire
community, we initiated a collaborative plan with the
Department of Environment to record road deaths while also
providing public education and opportunities for public involve-
ment.

As on many other islands, feral cats present a huge danger
to hatchling iguanas and small juveniles. This now has been rec-
ognized by the Cayman Islands Government, and we were
involved in an initial cat eradication program run by the
Department of Environment, the results of which are pending.
Encouragingly, a public education campaign indicated that res-
idents are aware of threats to “their” iguanas and enthusiastic
about protecting them from decline or extinction.

16 IGUANA  •  VOLUME 15, NUMBER 1  •  MARCH 2008 GOETZ

Volunteer Michael Vallee and the author taking measurements.

A
D

A
M

 M
IT

C
H

EL
L

Freshly road-killed adult female Cyclura nubila caymanensis.



IGUANA  •  VOLUME 15, NUMBER 1  •  MARCH 2008 17CYCLURA NUBILA CAYMANENSIS

Development presents a threat that often is less immedi-
ately noticeable but potentially very significant. As one of the
least developed Caribbean islands, Little Cayman is about to lose
its unique natural character as more and more of the beachside
lots are offered for sale. Numerous additional retirement homes
and resorts already are in the planning stages. A harbinger of the
pressure by investors is the new road crossing the island from
south to north in an area not associated with any immediate
benefit to the existing human population.

The relatively higher density of C. n. caymanensis around
houses and resorts might indicate at first glance that the species
could cope well with development and could survive on an
intensively developed Little Cayman. Maybe the iguanas are
indeed attracted out of their natural habitats toward human set-
tlement, possibly because of better and more abundant retreat
and basking sites, or perhaps because of additional food
resources provided by residents. However, cats and dogs,
whether feral or not, and road mortality are likely to act as neg-
ative forces in those population clusters. Also, as beach lots are

The author with a recently run-over and partially paralyzed adult
female on the North road.

A
D

A
M

 M
IT

C
H

EL
L

A typical sight along the coastal roads, where most land is advertised
for sale.

The newly constructed third road dissecting Little Cayman is clear evidence of the continuing development.



developed, the continuous disturbance and sealing of the ground
there will prevent sufficient recruitment as nesting locations van-
ish and hatchlings are killed by pets.

The difficulties inherent in assessing recruitment (i.e., reli-
ably detecting hatchlings and juveniles) present a major problem.
Until this can be overcome, a seemingly healthy co-existence of
(adult) iguanas in and around human settlements needs to be
viewed with great caution.

Cayman Brac
The population of C. n. caymanensis on the slightly larger island
of Cayman Brac (38 km2), which is 7.5 km from Little Cayman
and, with approximately 1,000 residents, much more densely
populated, is estimated at no more than 40 iguanas (Burton,
pers. comm.). Again, accurate data are missing and no thorough
study has been undertaken. Development on “The Brac” is
much more advanced than on Little Cayman, and feral cats and
dogs are abundant (Burton, pers. comm., Cottam, pers.
comm.), so that extirpation of the iguana population there seems
to be only a matter of time.

We will visit Cayman Brac during the next field seasons to
collect genetic material for comparison. If funding can be gen-
erated, a status assessment will be conducted, but without the
local commitment to tackle introduced predators, conservation
resources may preferentially be focused on Little Cayman.

The Future
In 2008, fieldwork is planned for the nesting season to allow
identification of coastal nesting areas and possible female migra-

tion routes to those areas. The focus will be on locating possible
communal nesting sites, which would then be a priority for pro-
tection. Little is known about the location of available nesting
sites in the interior of Little Cayman or where the females nest-
ing on the beaches have their territories. Therefore, identifying
migration routes would not only be of conservation concern,
but following females back to their original territories after nest-
ing could show us where to look for populated natural habitat
in the island’s interior. To facilitate this, we will fit as many as 30
female C. n. caymanensis caught on the beach after nesting with
radio transmitters, and then locate them several times a day until
they have been stationary for a number of days. Funding pro-
vided, in 2009 we will continue with more radio-tracking dur-
ing the mating season, when following roaming males could lead
us to other iguanas, allowing a more accurate estimation of over-
all population size.

Another focus from 2009 onward will be determining pop-
ulation sizes in the more densely populated areas, as well as
research into habitat parameters and what might attract iguanas
from natural habitats into disturbed areas (if this proves to be
the case). The results may well indicate whether this situation
could be halted or even reversed to attract a viable population
into protected areas, enhancing chances for the long-term sur-
vival of this subspecies on Little Cayman despite increasing
development.

Acknowledgements
Thanks are due to Adam Mitchell, Michael Vallee, and Jude
Bryja for their invaluable help in the field, and Fred Burton for

18 IGUANA  •  VOLUME 15, NUMBER 1  •  MARCH 2008 GOETZ

Adult Cyclura nubila caymanensis in the interior shrubland of Little Cayman.



IGUANA  •  VOLUME 15, NUMBER 1  •  MARCH 2008 19CYCLURA NUBILA CAYMANENSIS

his immense support and continued collaboration. The Cayman
Islands Government’s Department of Environment provided the
necessary permits and provided considerable support, as did the
National Trust for the Cayman Islands and its members on Little
Cayman. Durrell Wildlife Conservation Trust provided in-kind
support through professional time, and the Balcombe Trust gen-
erously provided all financial support. The International Reptile
Conservation Foundation facilitated the recruitment of volun-
teers. The manuscript was greatly improved by comments from
Kay Bradfield.

References
Gerber, G. 1996. Cyclura nubila ssp. caymanensis. In: IUCN 2008. 2008 IUCN

Red List of Threatened Species. www.iucnredlist.org.

Gerber, G. 2000. Lesser Caymans Iguana, Cyclura nubila caymanensis. 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.

Perera, A. 2000. Cuban Iguana, Cyclura nubila nubila. 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.

Other endemic species will benefit by sharing habitat conserved for iguanas. Two examples are this juvenile Little Cayman Trope (Tropidophis
parkeri; top) and this Cayman Galliwasp (Celestus maculatus; bottom).

The Slender Glass Lizard (Ophisaurus attenu-
atus) is a limbless denizen of the Midwestern
grasslands.

SU
ZA

N
N

E 
L.

 C
O

LL
IN

S,
 C

N
A

H

Ecology and Conservation of Grassland Vertebrates
The Sutton Avian Research Center, a unit of the Oklahoma Biological Survey
and the Oklahoma Chapter of the Nature Conservancy are hosting a conference
titled “Ecology and Conservation of Grassland Vertebrates.” The conference will
be held at the University of Oklahoma in Norman on 15–19 April 2008. For
more information, please see <www.suttoncenter.org/ecgv.html>.

Brenda D. Smith-Patten
Sam Noble Oklahoma Museum of Natural History




