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206 IGUANA  •  VOLUME 11, NUMBER 4  •  DECEMBER 2004 KÖHLER

Adult male Utila Iguana (Ctenosaura bakeri) relying on crypsis against a dead tree trunk in the mangrove swamps of Utila. Photograph
by John Binns.



IGUANA  •  VOLUME 11, NUMBER 4  •  DECEMBER 2004 207

Introduction

Ctenosaura, commonly known as Spiny-tailed Iguanas, is a
genus of Neotropical lizards in the family Iguanidae (Frost

and Etheridge 1989), which corresponds to the iguanines of
Etheridge and de Queiroz (1988). Ctenosaura includes 17 valid
species that are distributed from southeastern Baja California
and Sonora in western México and from Tamaulipas in eastern
México southward along both the Pacific and Caribbean ver-
sants through most of Central America to central Panamá
(Buckley and Axtell 1997, Grismer 1999, Köhler et al. 2000):
Ctenosaura acanthura (Shaw), C. alfredschmidti Köhler, C. bak-
eri Stejneger, C. clarki Bailey, C. conspicuosa Dickerson, C. defen-
sor (Cope), C. flavidorsalis Köhler and Klemmer, C. hemilopha
(Cope), C. macrolopha Smith, C. melanosterna Buckley and
Axtell, C. nolascensis Smith, C. oaxacana Köhler and Hasbun, C.
oedirhina de Queiroz, C. palearis Stejneger, C. pectinata
(Wiegmann), C. quinquecarinata (Gray), and C. similis (Gray),
as well as at least one undescribed species in the C. quinquecar-
inata-flavidorsalis complex (Köhler and Hasbun 2001; Hasbun
and Köhler, unpublished data).

Most ctenosaurs inhabit arid and subhumid areas in open
habitats such as dry forests and savannas. In the humid
Caribbean lowlands, Ctenosaura is relatively scarce and localized
in dry and open habitats. One species, the Honduran endemic,
C. bakeri, is exceptional because it lives exclusively in humid

mangrove forests (Köhler 1995). Ctenosaurs feed mostly on
plant matter, including leaves, flowers, and fruits. However, juve-
niles and, to varying degrees, adults also consume a variety of
invertebrates (mostly insects, crabs, and spiders) and vertebrates
(e.g., smaller lizards). All species reproduce oviparously with a
single clutch per year (Wiewandt 1982). However, ctenosaurs in
captivity have been observed producing two clutches 2–3
months apart (personal observation for C. bakeri). Whether
multiple clutches per season ever occur in the wild remains
unknown. Clutch size differs significantly between species: 2–4
eggs in C. defensor; 5–15 in C. bakeri, C. clarki, C. flavidorsalis,
and C. quinquecarinata; 11–33 in C. melanosterna; and usually
30–50, exceptionally to 88 eggs, in large species such as C. pecti-
nata and C. similis (Köhler 1996, 1997, 1998a). Duration of egg
incubation varies little across species, usually taking around 90
days at a temperature of 29–31 °C (Köhler 1997, 1998a).

Conservation Status of Ctenosaura
No species in the genus Ctenosaura is currently listed under the
Convention on International Trade of Endangered Species of
Wild Fauna and Flora (CITES). In México, only four species
(C. acanthura, C. hemilopha, C. pectinata, and C. similis) are
listed in the NOM-ECOL-059-94, first published in the Diario
Oficial de la Federacion on 16 May 1994. In this document, C.
similis and C. pectinata are listed as “amenazada” (threatened),

Conservation Status of Spiny-tailed Iguanas
(Genus Ctenosaura), with Special Emphasis

on the Utila Iguana (C. bakeri)
Gunther Köhler

Forschungsinstitut und Naturmuseum Senckenberg, Sektion Herpetologie, Senckenberganlage 25, D-60325 Frankfurt a. M., Germany (gkoehler@senckenberg.de)

Photographs by the author.

Abstract.—None of the species in the genus Ctenosaura are currently listed under the Convention on International
Trade of Endangered Species of Wild Fauna and Flora (CITES). Despite their protected status by national law
in México and most Central American countries, living specimens and eggs of the large species (e.g., C. acan-
thura, C. pectinata, and C. similis) can be found in markets or offered for sale along major roads by local people.
An increasing threat to some of the smaller species is the international pet trade. Species of Ctenosaura with small
geographic distributions are particularly vulnerable to these pressures, considerably more than their widely dis-
tributed congeners. The Utila Iguana (Ctenosaura bakeri), for example, is an endangered species endemic to Isla
de Utila, which is located off the Caribbean coast of Honduras. To preserve the Utila Iguana in its natural envi-
ronment, the “Conservation Project Utila Iguana” was founded in 1994. The main activities of the project include
a broad education and information program for the local community, investigations into the biology of the
species, a headstart program, and the protection of iguana habitat.

Key Words: Spiny-tailed Iguanas, Ctenosaura bakeri, México, Central America, Utila Island, Conservation

SPINY-TAILED IGUANAS

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208 IGUANA  •  VOLUME 11, NUMBER 4  •  DECEMBER 2004

whereas C. acanthura and C. hemilopha are listed as “sujeta a pro-
teccion especial” (with special protection) (Victor Hugo
Reynoso, personal communication). None of the other Mexican
species of Ctenosaura are listed.

Meat and eggs of most Ctenosaura are consumed by local
people throughout the Mesoamerican range of the genus (Fitch
and Henderson 1977, 1978). Despite being protected by
national law in most Central American countries, living speci-
mens and eggs of the large species (C. acanthura, C. pectinata,
and C. similis) can still be found in markets or offered by local
people for sale along major roads (unpublished observations for
Nicaragua, Honduras, El Salvador, and México, 1994–2001).

Iguana hunters still commonly sew the animals’ mouths closed
and pull out tendons to tie the legs together.

Some of the smaller species, such as C. quinquecarinata and
C. defensor, are considered to have medicinal properties if con-
sumed. In northern Nicaragua, local people believe C. quinque-
carinata to be venomous. As a result, they try to eliminate this
lizard whenever it is encountered. For example, they use small
rocks to block the entrance to C. quinquecarinata retreats in hol-
low fence posts, making it impossible for the animal to leave.
This usually leads to the death of the trapped iguana, evidenced
by piles of bones in blocked hollow posts (Hasbun and Köhler,
personal observations).

An increasing threat to some of the smaller species (espe-
cially C. quinquecarinata) is the international pet trade. We
found evidence of commercial hunting of this species in
Nicaragua. Even protected species endemic to countries that do
not allow ctenosaurs to be exported for the pet trade (e.g., C.
defensor from the Yucatán Peninsula, México) show up in inter-
national trade due to smuggling. In August 2000, ten living C.
defensor were confiscated at the Frankfurt airport by German
customs agents. A Mexican citizen had illegally shipped the ani-
mals hidden in a wooden pyramid addressed to a German citi-
zen. According to a written document found within the pyra-
mid, similar illegal transactions had occurred before this
shipment was confiscated (R. Simon, German Custom
Investigation Service, Frankfurt Branch, Wildlife Prime Unit,
personal communication).

Species of Ctenosaura with small geographic distributions
are more vulnerable to the pressures mentioned above than their
more widely distributed congeners. In light of this, the insular
forms deserve special attention. Off the northern coast of
Honduras in the Caribbean Sea is an island chain known as the
Bay Islands. The smallest and most westerly of these islands is
Utila, with an area of 41 km2. Despite its small size, Utila sup-
ports an impressive endemic ctenosaur, C. bakeri. Although four
juveniles of C. bakeri were collected in the late 1960s, the adults
were unknown to science until the early 1990s (de Queiroz
1990). In 1994, C. bakeri was rediscovered during an expedition
to Utila by the Senckenberg Museum (Köhler 1995).
Subsequent research revealed that this species is threatened with
extinction as a result of intensive hunting pressure by the local
community.

The Utila Iguana (Ctenosaura bakeri)
Ctenosaura bakeri inhabits mangrove swamps on Utila, which
cover approximately 6 km2 (14%) of the island. Temperatures
during the day range from 30–35 °C and nighttime tempera-
tures vary from 25–27 °C. Relative humidity ranges from
70–80% during the day to 95–100% at night. Males reach a
total length of 80 cm (maximum recorded snout-vent length =
31 cm; maximum recorded weight = 900 g); females are about
30% smaller. Given that C. bakeri prefers hollow branches and
trees as retreats, the few remaining old mangrove stands on Utila
with hollow branches and dead upstanding trunks provide the
most important habitat for iguanas on the island. The diet of C.
bakeri consists primarily of mangrove leaves, buds, and flowers
(Black Mangrove preferred), but also includes insects and crabs
(mostly Fiddler Crabs).

KÖHLER

Adult female Ctenosaura pectinata from Oaxaca, México.

Adult male Ctenosaura pectinata from Oaxaca, México.



IGUANA  •  VOLUME 11, NUMBER 4  •  DECEMBER 2004 209SPINY-TAILED IGUANAS

The breeding season for C. bakeri begins at the end of the
rainy season. Copulation has been observed between mid-
January and mid-March. During the nesting season (mid-March
through late April), females migrate from mangrove to sandy
coastal regions, covering distances up to a kilometer. The females
spend several days digging before they complete their nest bur-
rows. Burrows are composed of a tunnel approximately 40–60
cm long, reaching a depth of 25–40 cm, and ending in a nest
chamber with a diameter of 12–15 cm. Females lay from 5–19
eggs before backfilling the hole and leaving an air space over the
clutch. After egg deposition, females promptly return to the
mangrove swamp. The eggs incubate at a temperature of 30–31
°C, and juveniles hatch after approximately three months. In
contrast to the adults, young C. bakeri are usually observed on
dead wood near the ground. With the onset of the rainy season,
they start climbing higher in the vegetation. The uniform gray-
brown coloration of the juveniles is remarkable for the genus, as
juveniles of other Ctenosaura species exhibit either brown and
green markings (C. palearis, C. quinquecarinata) or are almost
entirely green (C. acanthura, C. hemilopha, C. pectinata, and C.
similis). The absence of green coloration in juvenile C. bakeri is
probably related to their preferred habitat. The young of this
species are ground dwellers who inhabit the edges of mangrove
swamps, where their gray-brown coloration provides excellent
camouflage. Together with fallen trees, the abundant aerial roots
of mangroves provide important hiding places for the juveniles
(Köhler 1995).

Conservation Project Utila Iguana
To preserve C. bakeri in its natural environment on Utila, I
founded the “Conservation Project Utila Iguana” in 1994 in coop-
eration with the Honduran Nature Conservation Office (AFE-
COHDEFOR) and German and international organizations.
Since 1997, this project has been a joint project of the Zoological
Society Frankfurt (ZGF) and the Senckenberg Nature Research
Society (SNG), Frankfurt. The primary goals of the project are to:
(1) develop a broad education and information program for the
local community, (2) investigate the natural history and repro-
ductive ecology of C. bakeri, (3) begin a headstart program, and
(4) protect iguana habitat on Utila. In addition, a survey of the
herpetofauna of Utila resulted in many new records for amphib-
ians and reptiles on the island, as well as the discovery of two
undescribed species of endemic anoles (Köhler 1998b).

With funding from the ZGF, the project’s Iguana Research
and Breeding Station was constructed and officially put into
operation on 25 April 1998. The Station makes effective and
continuous work possible, serves as a base for scientists and con-
servationists, and has become an important center for environ-
mental awareness and education on Utila. In 1999, a headstart
program was initiated with encouraging results. Our strategy is
to capture gravid females on nesting beaches and to move them
to enclosures equipped for nesting where they can deposit their
eggs in a safe environment. When egg laying is complete, the
iguanas are released at their site of capture. The spent females
swiftly return to the protection of the mangrove swamps, where,
without their eggs, they are of little interest to poachers. Using
this strategy, we are able to improve the likelihood that these par-
ticular animals will survive the current nesting season and repro-

duce again the following year. The eggs are then artificially incu-
bated in vermiculite at 28–32 °C. Half of the hatchlings are
released into the mangrove swamp immediately after hatching,
while the remainder is raised for 12 months to help surpass the
period of maximum vulnerability to predators.

The Visitor Center on the ground floor of the Station offers
an attractive presentation of information about the Utila Iguana,
as well as other aspects of Utilan flora and fauna, to both
Utilians and tourists. Informing the local people of the threats
to their unique iguana is vital to the long-term success of the
project. The people of Utila must become aware that this crea-
ture will disappear forever unless protective measures are imple-
mented. This presents a challenge, particularly given that the
islanders widely believe that replacement iguanas can be brought
in from the mainland if those on the island should die out. Only
through continuing education will local people become con-
vinced that the Utila Iguana exists nowhere else in the world.

Raising environmental awareness in children is of particu-
lar importance to the project. Since 1994, we have visited the
schools of Utila numerous times each year to work with teach-
ers and pupils regarding nature and species conservation on
Utila. Integrative tasks have been carried out with the students
in addition to slide shows.

An adult male Ctenosaura similis is about to be caught with a noose;
Yoro, Honduras.

Bound Ctenosaura pectinata in a market in Tehuantepec, Oaxaca,
México.



Once the Station opened, groups of schoolchildren could
visit and learn through public exhibits about the flora and fauna
of Utila and their endangered status. The problem of waste dis-
posal on Utila is also being addressed within the framework of
the education program.

Given that hunting and habitat destruction still occur, a
nature sanctuary will also be needed. Although the activities of
the project have been important and positive steps, iguana hunt-
ing has yet to be significantly reduced. While legislation exists
to protect the Utila Iguana, hunters are not actively deterred and
hunting continues daily. We commonly observed hunters with
three to eight adult iguana carcasses in their bags. During the
egg-laying season, hunters not only kill gravid females, but also
plow through beach sand to find iguana eggs.

Most recently, the Utila Iguana has become threatened by
destruction of its habitat. A large-scale international airport has
been opened on Utila, part of a rapid and extensive development
program that neglects to take ecological considerations into
account. Several new resorts and hotels are being built, as well
as a four-lane highway from the airport to the town. On the
north side of the island, where the most important iguana nest-
ing sites are located, beach areas have been “cleaned” by burn-
ing and divided into marketable lots. Once the beach areas have
been sold, the mangrove swamps will also be cleared and filled
with coral debris and garbage, similar to past activity on the
southern part of the island. Pristine sections of beach are crucial
egg-laying habitat for female Utila Iguanas. Without these nest-
ing areas, the Utila Iguana population will quickly decline as
development eradicates their nesting sites. Because these iguanas
have no other suitable place to lay their eggs, they will inevitably
begin their journey into extinction.

If conservation areas of considerable size cannot be estab-
lished in the face of this development, the future of Utilan ani-
mals and plants is not optimistic. Based on our field research and
because of their outstanding ecological value, the regions of Iron
Bound and eastern Rock Harbor would provide the most suit-
able core zone for a planned nature sanctuary. This core zone
contains rocky coast, beach (behind the rocky belt), Caribbean
dry forest, seasonal rain forest, and mangrove swamps. In this
area, we have been able to record all vertebrate species identified
on Utila to date (including the three endemic lizards), as well as
the three species of mangroves. In no other location on the

island are these five habitats found in such close proximity. The
connecting corridor to the Turtle Harbor Reserve would protect
other ecologically valuable and beautiful habitat, including the
oldest Red Mangrove forest, the mangrove area with the highest
density of epiphytes on the island, and extensive areas of wet
savanna. Most of the total area comprising the planned nature
sanctuary (the wetlands, mangrove, and wet savanna) is owned
by the community of Utila, and chances are good that protec-
tion of this area can be negotiated. On the other hand, all of the
beach areas and the Caribbean dry forest along the coast are pri-
vately owned and would need to be purchased to safeguard them
from development.

Aside from its ecological and conservation benefits, the cre-
ation of a nature sanctuary on Utila, if properly managed, would
provide the island with another tourist attraction. Through the
use of nature trails and guided tours in protected areas, visitors
could be given the opportunity to discover and observe a diver-
sity of unique reptiles and other animals in their natural envi-
ronment. Most tourism on Utila today is based on diving. By
persuading tourists to spend more time on the island, the nature
reserve would have a positive economic impact for the Utilan
community, as well as for Honduras as a whole. Simultaneously,
it would significantly enhance the long-term prospects for con-
servation of the biodiversity of Utila.

Acknowledgments
I am grateful to all the individuals, institutions, and organiza-
tions that have supported the Conservation Project Utila Iguana
in the past, especially to the Zoological Society of Frankfurt of
1858 – Help for the Endangered Animal World (ZGF),

210 IGUANA  •  VOLUME 11, NUMBER 4  •  DECEMBER 2004 KÖHLER

Adult male Ctenosaura bakeri from Utila, Honduras.

Subadult male Ctenosaura flavidorsalis from La Paz, Honduras.



IGUANA  •  VOLUME 11, NUMBER 4  •  DECEMBER 2004 211SPINY-TAILED IGUANAS

Frankfurt a. M., and the Senckenberg Nature Research Society
(SNG), Frankfurt a. M. Thanks are especially due to the many
volunteers who have done a wonderful job on Utila over the
years. I would particularly like to express my gratitude to John
Binns, Lutz Dirksen, Karoline Franz, Karsten Gees, Sven
Knapinski, AJ Gutman, Alexander Gutsche, Lori King, and
Sven Zoerner for the important work they are doing on behalf
of the Utila Iguana. Without their help the Conservation Project
Utila Iguana could never have taken place in its present form.

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Author Biography
Gunther Köhler is curator of herpetology at the
Forschungsinstitut und Naturmuseum Senckenberg,
Frankfurt am Main, Germany. He has published several
books and over 100 scientific articles. His research special-
ties are the taxonomy and biogeography of the amphibians
and reptiles of Central America, especially iguanid lizards.
Dr. Köhler has had extensive field experience in Central
America and has published the first two volumes of a book
series on the diverse reptilian fauna of Central America, now
available as a single volume in English. An English edition
of Spiny-tailed Iguanas is in preparation.

Environmental education: School children participating in a workshop
at the Iguana Station on Utila.




