




































Iguana 10.2


U
tila, site of the 2003 IIS Conference
(see related stories, p. 32 and 59), is the
smallest of the principal Honduran Bay
Islands (41 km2). This relatively tiny

body of land, however, supports a phenomenal
reptilian diversity (see Species Profile, p. 36) that
includes three native species of iguanas
(Ctenosaura bakeri, C. similis, and Iguana iguana)
— the only island so blessed anywhere in the
world.

27IGUANAJune 2003

UTILA:
Home to Three Native Iguanas

continued on page 30

Adult male Iguana iguana
at the Utila Iguana
Research and Breeding
Station. Photograph by
John Binns. Adult male Ctenosaura

similis; note the aggressive
reaction to the photographer
in the photo to the left.
Photographs by Sandy
Echternacht.

Adult female Ctenosaura bakeri on a mangrove branch.
Photograph by Robert Powell.

“Why do humans have an apparently
insatiable desire to take something natural
and beautiful, chop it down or kill it, cover 
it over with cement, and then proceed
immediately to the local lumber, nursery, 
and pet stores to purchase poor copies 
of what they just destroyed?”

John Binns, IIS Director



28 IGUANA Volume 10, Number 2

“Swampers,” as the endemic Utila Spiny-tailed
Iguanas (Ctenosaura bakeri) are called locally, are
arguably the most remarkable inhabitants of little Utila
Island. Differing from all other species of Ctenosaura,
which live almost exclusively in dry, open, sunny areas,
C. bakeri is limited to mangrove swamps.

Maximum known size is 315 mm (head-body
length) and 923 g for males and 229 mm and 424 g for
females. Although ctenosaurs often are called “Black
Iguanas,” Swampers are relatively colorful. Juveniles are
largely uniformly blackish-brown with a few darker
brown stripes on the upper side of the body and tail
(coloration that renders them quite cryptic against the
muddy substrates of the swamp). Adults, in contrast,
vary from grayish-brown to an amazing turquoise,
which is most obvious in bright sunlight.

Living exclusively in a mangrove swamp requires
special adaptations, including the need to deal with a
salty diet and the lack of
freshwater. In addition,
the substrate is muddy
and frequently sub-
merged during high
tides, forcing Swampers
into the trees — where
the only retreats are nat-
urally occurring tree

holes. Suitable trees with holes are very much in
demand. Juveniles and adults are strongly territorial and
will strenuously defend their home trees even against
larger opponents. Tree holes are mostly restricted to
older mangroves, especially Black Mangroves (Avicennia
germinans), which are scattered on Utila. The result is a
patchwork-like distribution of C. bakeri, even in other-
wise apparently suitable habitat.

The few other reptiles known to be mangrove spe-
cialists are exclusively carnivorous. Swampers, however,
are omnivorous. Mangrove leaves and, if available, man-
grove flowers form the main part of the diet. The second
largest part of the diet is fiddler crabs, which have been
found in 72% of analyzed scat. To catch crabs, iguanas
wait for low tide and either forage actively for prey or,
usually with more success, employ a sit-and-wait strat-
egy until a crab crawls within range. The fact that man-
grove leaves contain only 7% crude protein versus 34%

in crabs may explain the
intensive efforts to hunt
crabs. Both mangrove
leaves and crabs are salty,
which creates an osmotic
problem for Swampers.
Since freshwater is avail-
able only during the rainy
season, water usually is
acquired with food
(50–70% water) or by
drinking the brackish
swamp water. Reptilian
kidneys are unable to
excrete excessive salt, so
most is eliminated by spe-
cialized salt glands located
in the nasal cavity. In effect,
the salt is sneezed out.

Reproductive activity
occurs during the dry sea-
son. Triggered by decreases
in rainfall (to <200 mm/m2)

and increases in air temperature (to >24°C), usually from
late January through March, adult males begin patrolling
the invisible border around a mating territory, using dis-
plays and aggressive behavior to exclude male intruders.
Egglaying takes place from mid-March through early
May, when the ground temperature is about 30°C.
Hatching usually occurs from mid-June to early August,
before the onset of the next rainy season. In association
with recent warming trends, a shift of the entire repro-
ductive season to as much as two weeks earlier has been
recorded.

Because of the saturated substrate, gravid females
must migrate to nesting sites, which are restricted to a
few sandy beaches. Females may travel up to 1.3 km

Utila Island Swampers 
Alex Gutsche

Humboldt Universität, Berlin

An adult male “Swamper” (Ctenosaura bakeri) basking
on a mangrove stump near the canal. Photograph by
A.C. Echternacht.

Adult male Ctenosaura
bakeri from Iron Bound.
Photograph by Robert
Powell.



29IGUANAJune 2003

(direct line) to lay their eggs before returning to their
home tree in the swamp. Nesting sites must have sandy,
well-drained soil and realize an average incubation tem-
perature of 30.5°C. Females stay at the beach for sev-
eral days, searching for a suitable nesting site at up to
50°C surface temperatures. Nesting tunnels range from
510–1240 mm in length and nesting chamber are at
depths of 150–450 mm. Clutches contain 6–16 eggs.
Three months later, hatchlings emerge and head
straight for the mangroves.

Large Brown Basilisks (Basiliscus vittatus), Great-
tailed Grackles (Quiscalus mexicanus), raptors, and
snakes all prey on juvenile iguanas, but only large boas
(Boa constrictor) pose a significant threat to adults.
Consequently, the major threats to C. bakeri are
increases in uncontrolled human development and the
consequent loss of habitat.

The total range of C. bakeri on Utila consists of
three separate mangrove areas with a total area of
about 10 km2. Egglaying areas are much more limited
and have a total size of less than 1 km2. As a result,
Utila Iguanas have the smallest and most threat-
ened distribution of any ctenosaur. Population
numbers will invariably decrease in the near
future if the habitat, especially the nesting areas,
becomes unavailable.

Although, hunting still occurs despite regulations
against it, tourism and land sales that are increasing the
extent of Utila Town are of greater concern. These
result in deforestation or despoilment of mangrove
areas with landfills. Sandy beaches are in great demand
for development, so nesting sites close to town are
cleared of debris, rendering them unsuitable for
iguanas even before construction begins. Invasive
plants also overgrow the open nesting sites and must
be controlled.

Protection of suit-
able mangrove areas
and nesting sites is criti-
cal — and must be
implemented as quickly
as possible. All beaches
are privately owned, 
so purchasing key
stretches for the use of
iguanas is the only solu-
tion. Creating an iguana
refuge on Utila will
enhance the likelihood
of the Utila Iguana’s
long-term survival and
also would serve to pro-
tect areas used as roosts
by migratory birds and
as nesting sites for 
critically endangered
Loggerhead and
Hawksbill turtles.

A female Ctenosaura bakeri on a mangrove stump.
Photograph by John Binns.

The distribution of Ctenosaura bakeri on Utila Island (gray areas) corresponds closely to
stands of old mangrove forest, especially large Black Mangroves with tree holes. Females
must migrate to nesting beaches (dark gray) in order to lay their eggs. All nesting beaches
are in imminent danger of development. Other threats to the species are indicated with
X’s: the area near West End is being deforested; Utila Town, especially near the new
airstrip, and Pretty Bush are expanding into Swamper habitats and garbage is being
dumped into the mangrove forests; iguanas in areas near East Harbor, Rock Harbor, and
Red Cliff remain vulnerable to hunting, which continues despite prohibitions. Modified
from a figure by Alex Gutsche.



As might be expected when three large species
with generally similar lifestyles occupy such a small
area, they must in some way partition the severely
limited resources in order to avoid direct and
mutually disoperative competition. In fact, these
iguanas are largely restricted to distinctly different
habitats. Green Iguanas (I. iguana) inhabit the
remaining upland forests, where continuous
canopies allow them to remain inconspicuously
hidden in the treetops — except when the females
are forced to descend in order to nest. Black
Iguanas (C. similis), referred to locally as
“Highlanders,” favor more open areas, occupying
forest edges and rockpiles, fallen logs, or isolated
trees in otherwise open fields. These lizards are
quite capable of effectively utilizing heavily dis-
turbed areas and frequently coexist closely with
humans (seeing individuals basking on rooftops or
along heavily traveled roads is quite common).
Unlike Green and Black iguanas, both of which
have broad distributions throughout the entire
Neotropics and Middle America, respectively, the
Utila Iguana (C. bakeri) is found only on Utila.
Possibly because of their smaller size or more retir-
ing nature, Utila Iguanas are found only in the
apparently inhospitable mangrove swamps, where
they fare quite well on a diet of mangrove leaves
supplemented with small fiddler crabs. Known to
the local Utilians as “Swampers,” Utila Iguanas do
face a problem when nesting seasons roll around.
Since the swamps are regularly inundated and the
soils totally saturated with brackish water, they are
unsuitable nesting sites. Instead, females must
migrate considerable distances to one of the rela-
tively few sandy beaches (only 38 ha on the entire
island) to lay their eggs. Interestingly, when they
return, they reestablish residence in the very same
mangrove they left some weeks before. How they
find their homes with such inerring accuracy
despite the bewildering similarities of one tangled
tree and the next is one of several mysteries sur-
rounding this ecologically unique iguana.

* Upon recommendations by the IIS, consideration is being
given to holding hatchlings until two years of age, when
chances for survival are greatly enhanced.

Brief History of the Iguana Station

Karsten Gees, Director
Utila Iguana Research and Breeding Station

The story began with an American Consul at
the end of the 19th century. While visiting Utila,
he collected some iguanas in the mangroves and
sent them to the Washington Zoo. The zoo direc-
tor, a Mr. Baker, sent these animals to the famous
herpetologist, Leonhard Stejneger at the National
Museum of Natural History in Washington, DC.
Stejneger determined that the iguanas of Utila
were a new species, and he described them for-
mally in 1901, giving the Utila “Swamper” the
name Ctenosaura bakeri in honor of Mr. Baker.

The herpetological world essentially forgot
about C. bakeri until 1994, when a group of
German researchers led by Gunther Köhler redis-
covered these iguanas in the wild. In the following
years, the group determined that C. bakeri is
endemic to Utila and that its habitat is restricted to
the mangrove swamps, with a total area of only 8
km2 (see article on p. 28). Furthermore, they
found that C. bakeri is threatened by hunting and
by the unchecked development of infrastructure
for the burgeoning tourist industry. Thus was born
the Conservation and Research Project Utila
Iguana. In 1997, a breeding program was estab-
lished to support the wild population. Half of the
hatchlings each year are released immediately to
the wild while the others are reared at the Station
for one year* before release. Concurrently, an
ongoing research program was initiated for the
study of the distribution and behavior of the Utila
Iguana. The Zoologische Gesellschaft Frankfurt
and the Senckenbergische Naturforschende
Gesellschaft Frankfurt have been the principal sup-
porters of the project and enabled the original
acquisition of property and construction of the
Iguana Research and Breeding Station in 1998.

The Iguana Station continues to grow and
improve. It now has a visitors’ center with exhibits
focusing on C. bakeri, but also addressing the
other reptiles and amphibians of Utila. Spacious
cages have been constructed on the grounds for
rearing hatchling Swampers, along with cages for
Green Iguanas (Iguana iguana) and Black
Iguanas (C. similis), both species of which also are
native to Utila. About 100 tourists visit the Station
each month.

30 IGUANA Volume 10, Number 2

continued from page 27



31IGUANAJune 2003

An adult male
“Swamper” (Ctenosaura

bakeri) at the Research
Station. Photograph by

John Binns.

Main building at the
Iguana Research and
Breeding Station.
Photograph by John
Binns.

Outdoor enclosures
for head-starting

iguanas. Photograph
by John Binns.



In addition to maintaining the breeding and
research program, volunteers from all over the
world provide environmental education programs
for the local schools. In cooperation with BICA
(Bay Island Conservation Organization), the other
NGO on Utila, all grades have been covered this
year. The goal of this outreach program is to
enhance the sensibility and feelings of responsibil-
ity of the children for their island home, with its
phenomenally abundant natural treasures. Last but
not least, the Iguana Station is working with the
IIS and other organizations to acquire funding for
the purchase of beach properties that serve as nest-
ing sites for C. bakeri and which are, at the
moment, the most critically threatened portions of
their habitat (see related story on p. 28).

The Zen of Swamping — 
Adventures on Utila

AJ Gutman

What do you do when you’re dripping with
sweat and knee-deep in fetid swamp mud that
threatens to yank the boots off your feet with
every step? You scramble to capture another tiny
Fiddler Crab to stuff in your cargo pockets (to
feed to the young Utila Iguanas in the rearing
cages at the Iguana Research and Breeding
Station). Eyes alert for an endangered “Swamper”
(as the endemic mangrove swamp-dwelling
iguana, Ctenosaura bakeri, is known locally), you
reach for the hand of a smiling friend as you climb
onto a sturdy mangrove root, ready to lend a hand
to the next person stuck in the mud. As muddy
hands meet, you both burst into laughter, repeat-
ing “smacks of adventure!”

Perhaps not everyone would answer that ques-
tion in quite the same manner, but all of the par-
ticipants in the 2003 International Iguana Society
conference on Utila definitely would. Seventeen
IIS members and assorted other conservation afi-
cionados from around the world spent a week
together on Utila, a small island off the northern
coast of Honduras. Much of that time was devoted
to trekking through wet and muddy Swamper
habitat.

Our hosts included personnel from the Station
on the island and Dr. Gunther Köhler, Director of
the Conservation Project Utila Iguana (CPUI),
from Frankfurt, Germany. I first read about Dr.
Köhler and his research and conservation work on

32 IGUANA Volume 10, Number 2

Organizations that have supported the Conservation 
Project Utila Iguana: the Senckenbergische Naturforschende
Gesellschaft Frankfurt, the International Reptile
Conservation Foundation, and the Zoologische 
Gesellschaft Frankfurt.

Only true iguana lovers (i.e., IIS members) could have this
much fun on a stomp through the swamp. Photograph by
John Binns.

John Binns, representing the International Reptile
Conservation Foundation (IRCF), installed about
$2,500 in computer and network equipment in the
lab at the Utila Iguana Research and Breeding Station.
This replaced aged equipment and dramatically
improved the Station’s ability to communicate while
also aiding in its research efforts.
David Nieves and Rick Morrow, representing the
Kansas City Herpetological Society (KCHS), donated
about $500 worth of equipment including two
electronic scales (full-size for the lab and a miniature
version for use in the field), a Gentle Giant Tong®, and
a selection of tools including forceps, hemostats,
dosing needles, and probes. All of these items were
purchased from Midwest Tongs (www.tongs.com).



behalf of the remarkable Swamp Iguana years ago in
the Iguana Times. Eager to meet him and his wife
Elke, I was entirely prepared to be dumbstruck with
awe. What I didn’t expect was a warm and wonder-
ful couple with whom I would make my country
and western singing debut performing Gunther’s
original rendition of the “Swamper Song.”

The Station also proved to be delightful.
Walking there from
where we were staying,
we would regularly
encounter several Black
Iguanas, Ctenosaura
similis, that had taken
up residence in hollow
trees and on piles of
rocks along the edges
of Utila Town. The
Station “greeter” was
Rosalita, a charming
Red-naped Amazon
Parrot who loved to
have her neck
scratched. The tidy
grounds were dotted
with Hibiscus flowers
and spacious enclo-
sures filled with hatch-
ling C. bakeri, as well
as a few C. similis and
Iguana iguana that are
used in environmental

education programs for Utilian school children.
Among my personal favorite animals were the
large Swamper male, who I named Willy Nelson
because of his long dorsal spines, and a gorgeous
female I called “Marlene.” Marlene is an astonish-
ing hybrid between C. bakeri and C. similis. Half
of her tail, divided along the midline, has scalation
characteristic of C. bakeri and the other half is
characteristic of C. similis!

One of our field trips was by boat through a
mangrove-covered canal where we were delighted
by numerous Swamper sightings. Our final desti-
nation that day was a beach in an area called “Rock
Harbor,” where we cleared exotic invasive vegeta-
tion choking important egg-laying sites. What we
didn’t know while we were doing this work is that
this area is one of the few remaining beach sites
available for purchase. In cooperation with the
CPUI and the International Reptile Conservation
Foundation, the IIS is initiating a fundraising

33IGUANAJune 2003

Gunther Köhler (right), indulging his passion for country
and western music, is joined by his wife, Elke (center), and
AJ Gutman (left), performs the “Swamper Song” for
conference participants. Photograph by John Binns.

A juvenile “Highlander”
(Ctenosaura similis) on a rock wall.

Photograph by Robert Powell.

Rosalita, a Red-naped
Amazon Parrot, was the
Station “greeter.”
Photograph by Joe
Burgess.

A Swallowtail Butterfly visits a
Hibiscus flower at the Station.
Photograph by Robert Powell.



effort to help purchase and preserve this area for
the Utila Iguana (details are given in the letter
from the President on p. 59). This site also is part
of the proposed Ecotrail, which will allow tourist
access to critical iguana habitat for the economic
benefit of the island while minimizing impact on
the endemic species.

Another field trip to the Big Bight took us past
an extremely unattractive garbage dump (Utila
currently has no formal plan for waste disposal and
the risk of contamination to groundwater is very
real). Given the number of Anolis enthusiasts in
our group, many people were eager to hunt for
the endemic Anolis utilensis (a really swell anole
found in the swamp; see the Species Profile on p.
36). Up to our knees yet again in water-inundated
swamp, we happily climbed trees in pursuit of lit-
tle lizards under the watchful and amused gaze of
a Black Hawk.

Additional hikes, in which at least some of the
conferees participated, went through prime
Swamper habitat to Iron Bound on the northern
coast, to the beaches below Pumpkin Hill, which
were graced by colorful “Shaky Paws” (see the
Species Profile), and, after a long boat trip around
the western tip of the island, on an unsuccessful
search for Don Quickset Pond, freshwater home

to the few turtles known to occur on Utila.
Although the pond remained elusive, hikers on
that trip did manage to find a frog, one of five
species known from the island but rarely seen
except during the rainy season.

34 IGUANA Volume 10, Number 2

An educational sign near the harbor promoting Swamper
conservation. Photograph by John Binn.

“Marlene,” a female hybrid
Ctenosaura bakeri x similis.
Photograph by John Binns.

“Willie Nelson,” an adult
male Swamper at the Station.
Photograph by Robert Powell.



After showering off the mud, we spent our
evenings at the Bush Bar, a wonderful open-air
pavilion, which the owner had graciously offered
as a venue for our presentations. Conference par-
ticipants, Iguana Station staff, and several Utilians
were treated to talks on “Spiny-tailed Iguanas,”
“Aspects of the Ecology and Population Biology

of Ctenosaura bakeri,” “Lizard Ecology on West
Indian Islands,” “Lizard Wars” (invasive versus
native reptiles in Florida), and “Modern
Conservation Practices in the Caribbean.”  

35IGUANAJune 2003

Gunther Köhler addressing the conference. Photograph by
Alex Lau.

AJ Gutman, Joe Wasilewski, and Betsy Davis engage in
some hands-on conservation by clearing invasive vines that
are choking an important nesting site near Rock Harbor.
Photograph by John Binns.

A Common Black
Hawk (Buteogallus

anthracinus)
supervising our

Anolis hunt in the
Big Bight.

Photograph by
Robert Powell.

Bob Powell, Sandy Echternacht, Alex Lau, Wendy
Townsend, Mark Keoppen, and an unnamed boat driver
(from front to back) heading for and through the canal to
Rock Harbor. Photographs by Joe Burgess.

The only frog (Leptodactylus melanotus) seen
on the trip. Photograph by Joe Burgess.

The IIS thanks Gunther Köhler, Sven Zörner, Alexander
Gutsche, Karsten Gees, and the volunteer staff of the
Iguana Research and Breeding Station for making our
Conference an unforgettable experience. Special
thanks also to the thoroughly wonderful Sandy Binns
for making all of our impossible travel arrangements.
We never could have done it without you!


