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IGUANA  •  VOLUME 11, NUMBER 1  •  MARCH 2004 55THE IGUANA

Characteristics of the genus Iguana Laur. [translator’s note:
“Laur.” refers to Josephus Nicolaus Laurenti, who first for-

mally described the Common or Green Iguana] include the
elongate, laterally compressed body, a large, quadrangular head,
a short neck, powerful limbs, exceedingly elongate toes, and an
extremely long tail with keeled scales throughout, a distinct
dewlap with an anterior border of spike-like scales, a middor-
sal row of enlarged spines that extend from the nape to the tip
of the tail, multi-sided head scales of various sizes with alter-
nately arched, tuberculate, or keeled surfaces, smooth or slightly
keeled ventral scales, triple-keeled scales on the undersides of

toes, distinct femoral pores, a large, round tympanum, wide
nares, and dentition with the anterior-most teeth peg-like,
sharp, and with a slight inward tilt, and others three-edged and,
distinct from most related genera, serrated along the edge. In
addition to the jaws, the sphenoid and pterygoid bones also
bear a double row of small teeth, the numbers of which, like
those on the jaws, vary by age.

The iguana, Iguana tuberculata Laur. [an alternative name
for Iguana iguana that was widely used well into the 20th cen-
tury], reaches 1.4–1.6 m in length, of which 1 m or more con-
sists of tail. Ground color is an attractive leaf green. Very young
individuals lack markings, but the rump and tail of larger ani-
mals bear distinct dark, often light-outlined crossbands. The
underside is white or yellowish.

All iguanas are found in tropical South America, the
nations surrounding the Gulf of Mexico, and several of the
Lesser Antilles. All live in trees, particularly those along the
banks of streams or lakes. There they move about with consid-

H I S T O R I C A L  P E R S P E C T I V E S

Iguana, Iguana tuberculata Laur. 1/7
natural size. Photograph from the
Zoological Garden in Frankfurt
a/Main by A. Fahr-Darmstadt.

The Iguana1

Franz Werner

1 Excerpted and translated from Franz Werner (1913. Die Lurche und
Kriechtiere von Alfred Brehm. Zweiter Band: Kriechtiere
(Schuppenkriechtiere), pp. 92–98 + table “Lizards IV,” no. 3. In: O. z.
Strassen (ed.), Brehms Tierleben. Allgemeine Kunde des Tierreichs. 4th ed.
Bibliographisches Institut, Leipzig and Wien. Translated by R. Powell.



erable dexterity, climbing or jumping from limb to limb. They
also are quite adept at retreating into the foliage, rendering
themselves invisible to the untrained eye. Toward evening, they
frequently descend to the ground in order to forage — but, if
threatened, they rapidly seek the highest branches whenever
possible, or, as we already know, the depths of any nearby water.
In the latter, they are as much at home as monitors [these are
generally large lizards in the family Varanidae; all are found in
the Eastern Hemisphere; some are quite aquatic in their habits].
The powerful tail is used as a combination oar and rudder and
is capable of propelling them with surprising speed. They swim,
as do all lizards, with all four limbs securely adpressed along
their bodies, relying exclusively on their tails for propulsion and
steering. In such a fashion, they are fully masters of the water.
In addition, they are equally as adept at diving as at swimming,
and are capable of spending considerable periods of time sub-
merged in the depths. They do not tire while under water and,
as a consequence of their skill, effectively evade any dangerous
enemies unable to follow them into what is essentially a foreign
element. They seem not the least concerned about crocodiles
or caimans, many of which are found in the waters into which
these lizards unhesitatingly venture.

Duméril [André-Marie-Constant Duméril, the foremost
taxonomic herpetologist of his era] noted that he found only
plant materials in all of the iguana stomachs he had examined,
and others have agreed. Sumichrast [a naturalist] indicated that
soft berries had been consumed in such quantities by the speci-
mens that he had dissected that their intestines were extraordi-
narily distended. Tyler [another naturalist] indicated that,
among the half-digested leaves he had found in the digestive
tracts of iguanas, were innumerable quantities of small worms
that, he assumed, had been on the leaves consumed by the
lizards and inadvertently swallowed. The main dietary compo-
nent surely consists of plant materials such as fruits and leaves,
but we also know beyond any doubt that younger animals gladly
take insects and, as testified by Tyler, earthworms and snails.

Typically, adults flee at the first sight of humans, mainly
because they have learned to view them as their most dangerous
enemy. In contrast, young animals sit quietly and are conse-
quently easy to catch. However, if iguanas are forced into a cor-
ner, they defend themselves valiantly, initially inflating their bod-
ies, extending their dewlaps, and hissing, then jumping at their
opponent while attempting to bite. Once their jaws have a firm
grip, they are quite unwilling to let go. Because the overlapping
molars are very sharp, they leave a bite that bleeds freely, much
like a wound caused by a knife. At the same time, the tail is used
to inflict powerful, painful, and even dangerous blows.

During the breeding season, iguanas are said to be even
more excitable and considerably more aggressive than usual,
never leaving a chosen female while furiously attacking any ani-
mal that ventures too near. Even battles among males for pos-
session of females are grim and frenzied. Well after the breed-
ing season, females appear in the vicinity of sandbanks, in
which they intend to lay their eggs. During this period, one can
most readily see these animals, which typically spend the rest of
their lives making every effort to remain invisible. On St. Lucia,
egg deposition occurs during the months of February, March,
and April. The eggs are about the size of those laid by pigeons,

white or light straw-yellow in color, and have soft shells, the lat-
ter reminiscent of fine glove leather. Like those of most reptiles,
the eggs are composed almost entirely of yolk. The females lay
the eggs in holes dug in the sand, which they then carefully
cover. Beyond that, they show no concern for the brood.
However, Göldi [Emílio August Goeldi, a Swiss-born Brazilian
naturalist for whom the famous Goeldi Museum in Pará at the
mouth of the Amazon River was named] noted that a captive
female attacked him vigorously as he attempted to examine her
recently deposited eggs. Reports indicate that older females lay
considerably more eggs than younger individuals. A female held
in captivity by Göldi, for example, laid five eggs on one day and
32 more five days later. In a series of dissected specimens, 8, 14,
and 17 eggs were found in increasingly larger females. Eggs
were arranged in distinct rows on each side of the body cavity
and were all about equal in size. Sumichrast noted that, in his
experience, several females commonly laid eggs in a communal
nest, so that one could on occasion find as many as ten dozen
eggs in a single cavity. Many eggs are destroyed not only by ants
but also by small mammals, especially the so-called muskrat
found on St. Lucia [not the better known muskrat of North
America]. Consequently, female iguanas may purposely seek
out the seacoast, the sand of which is considerably less accessi-
ble to its enemies than the banks of rivers. Hatchlings appear
to stay together for extended periods, as A[lexander]. v[on].
Humboldt [another famous German naturalist whose explo-
rations of South America thrilled Europe and inspired Darwin]
mentioned that his guide showed him a nest filled with 10 cm-
long iguanas. “These animals were hardly distinguishable from
a common lizard; the prominent dorsal crest scales, the large,
erectile scales, and all of the dangling appendages that provide
the iguana, when he is 1–1.5 m long, with such a fierce coun-
tenance, were barely present in these beginners.”

In the West Indies, the idea that iguana meat is unhealthy
is prevalent throughout the region. Nevertheless, no one pays
much attention to that opinion, searching instead, almost with
the same zeal as the members of Schomburg’s party [reference
unknown], for such tasty table fare. Catesby [Mark Catesby, an
English naturalist] said that iguanas were common and prof-
itable trade goods, caught by hand and passed along, until, in
the end, they were bought as delicacies by rich mainlanders. The
meat is considered to be easily digestible, nourishing, and tasty;
it is fried or, more frequently, stewed. The eggs, which do not
harden with cooking, are almost devoid of eggwhite; they are
typically used in the preparation of broth. Talented collectors
specialize in the search for this rather wonderful fare and use sev-
eral different methods to capture animals. One of Schomburg’s
reports describes a rather unusual technique that some have dis-
puted but several other writers have mentioned. Because the
lizards are reputed to be quite curious, they extend their heads
when approached, allow themselves to be stroked with a belt
until it is tightened sufficiently to allow the animal to be effec-
tively noosed. Once firmly in place, the tether is used to force-
fully tear them from their arboreal perches. The iguanas obvi-
ously fight like crazy to free themselves, opening their powerful
jaws, snarling and hissing — but, of course, are easily over-
whelmed. The snout is secured with a loop of string and the
body and limbs are tightly strapped. In this helpless position, the

56 IGUANA  •  VOLUME 11, NUMBER 1  •  MARCH 2004 WERNER



IGUANA  •  VOLUME 11, NUMBER 1  •  MARCH 2004 57THE IGUANA

iguanas are then taken to the market. I am loath to decide just
how much if any of this tale is true. I do consider it possible that
these curious creatures allow the collector to approach closely, at
least in areas where they are seldom hunted. More commonly,
trained dogs are used, particularly since, without their help, find-
ing the lizards, artfully hidden amongst the foliage, is almost
impossible. Liebmann [yet another naturalist] reported that,
along the west coast of Central America, lizards are ambushed
and cornered by dogs when they descend from their trees in the
evening, Tyler expanded on this by noting that dogs were
trained specifically for this task. Experienced dogs probably use
their sense of smell to locate iguanas and then bark to draw the
hunters to the tree in which the lizard is roosting or, if encoun-
tered on the ground, hold it until their masters arrive. Some
dogs undoubtedly do not hesitate to grab the iguana by its back
and shake it until it dies. For all that, a few dogs, those that have
learned from experience and those that aren’t particularly bright,
fear the tail and teeth of a frenzied and frightened iguana. If the
lizard does manage to flee, it almost invariably turns first to a
tree; if, however, unable to find one quickly, it will just as read-
ily seek shelter in a cave or crevice — in either case, it is proba-
bly lost. An iguana, seemingly secure in the foliage, is relatively
easily shaken from a perch or the branch on which it rests can
be cut. If in a cave, an iguana will often think itself secure if only
its head is hidden. Once successfully in hand, in order to pre-
vent being bitten, the hunter will run a tough stalk through the
skin under the chin and out a nostril; tying the ends to render

the mouth secure. Then, using the long tendons of the middle
toes, the limbs are secured behind the back. Thus trussed, the
tortured captive is taken to market the next morning. Because
Mexicans are very familiar with the tenacity of iguanas, that
often escape even after being shot in the body, such securely tied
individuals may be held for months until eventually sold. This
often occurs prior to festivals, during which iguanas are partic-
ularly prized when baked in corn tortillas and eaten as delicacies.
They also may serve as special gifts.

Occasionally, one might find among the entrails what
appears to be half an egg. In earlier times, these were consid-
ered to be powerful drugs with great healing properties, and
may, from place to place, still be viewed as such today.

Initially, captive iguanas are wild and may be particularly
vicious, biting their masters and threatening any animal that
ventures too near. They may even kill weaker pets that enter
their domains, including fellow captives. Over time, their fren-
zies calm and, in the course of several weeks, they become so
tame that anyone can touch them.

Emílio Goeldi on Iguanas
Of recent observers, Goeldi in particular has contributed greatly
to expanding the horizons of our knowledge about the lifestyles
of iguanas. “The iguana, commonly called ‘camelaão’ by
Brasilians, is encountered with increasing frequency as one pro-
gresses from Bahia to the north. Sightings in the vicinity of the
Amazon River and along the coast of Guahana are daily occur-

Iguana, Iguana tuberculata Laur.
1/6 natural size.



rences, with an understanding that, within such larger regions,
specific sites with proper topographical and vegetative features
will be preferentially occupied. Conversely, iguanas avoid local-
ities that fail to provide the resources necessary for survival. This
is particularly evident, for example, here in Pará [the Brasilian
state at the mouth of the Amazon]. Single iguanas are encoun-
tered only from time to time in the vicinity of the city and on
adjacent islands. In contrast, during a short rowboat ride along
Marajó Island, especially its southeastern part, one can see hun-
dreds of individuals. I’ve also found them to be astonishingly
common at Cape Maguarí and along the Atlantic Coast. Such
numbers of iguanas inhabit several smaller islands, located from
the immediate vicinity of Cape Maguarí to several hours away,
that they are rightly considered to be their most abundant
inhabitants and, further, over time they have proven themselves
capable of dramatically altering the vegetation. I am quite
familiar with two of these little islands, ‘Ilha Camaleão’ and
‘Ilha Machados,’ the latter of which I visited in early September
1896. Our gracious host, the owner of the island (and, coinci-
dentally, the discoverer of Lepidosiren paradoxa on Marajó),
blamed the untold numbers of iguanas living on the island for
the extirpation of the native mangrove forest.

“The iguana is a vegetarian of the purest sort, a fact that,
to my surprise, I fail to see reflected in the herpetological liter-
ature. Just in the immediate vicinity, iguanas make a major
impression on the constitution of the plant communities; for
example, on (1) mangrove trees (Avicennia), (2) thorny aturia
bushes (Drepanocarpus), and (3) quick-growing anhinga stands
(Montrichardia). These three plants obviously serve as the main
foods for iguanas.

“During most of each year, the iguanas, as is characteristic
of the species, live a happy and worry-free life in this hot, moist
climate — as long as something to eat is available. A paucity of
food is not likely in most cases, unless one is dealing with an
isolated island, such as the examples cited earlier, combined
with an overpopulation of lizards. In such cases, largely as a
consequence of their own actions, iguanas may experience hard
times during the dry seasons in these deserts of their own
design. Animals may be severely emaciated and so feeble that
they are hardly able to move. Such instances arouse our pity,
particularly in contrast with their brethren who thrive along
riverbanks where an abundance of fare prevails.

“If one glides slowly and quietly along in a rowboat, one
can see iguanas left and right, so to speak, at every step. Some
are perched on the highest branches of the airy mangroves,
whereas others rest among the colorful garlands of the
arribidaea bushes. The inexperienced novice first notices the
older, larger individuals whose boldly patterned bodies are quite
evident. In contrast, a more practiced eye is necessary to see
juveniles or lizards that have recently shed. While basking
motionless on their perches in the hot sun, their beautiful green
dresses blend seamlessly with the juicy leaves of the vines that
often garnish the tops of the anhinga bushes. As a rule, they
hold their positions until one approaches all too near — but
once the decision is made to flee, one is astounded by their
unexpected adroitness. Iguanas are masterful swimmers and
divers, and an individual that falls in the water must be con-
sidered lost unless bearing deadly wounds. Killing an iguana is

not easy. They are unbelievably tough, and only a shot through
the head or vertebral column will guarantee a catch.

“By the end of August, one begins to find gravid females
about ready to lay their eggs. Yellow ovarian follicles collectively
resemble a voluminous cluster of grapes that take up consider-
able space in the body cavity. My impression, for example, near
Cape Maguarí, is that females are definitely in the minority. At
least, we found on the average of up to four or five males for
every female. This comment should be accepted with reserva-
tions, however, because I cannot be sure how much of a role
chance has played in these encounters, or if humans have not
affected the gender ratios. I had the opportunity to convince
myself that the latter possibility could occur, mainly by local
inhabitants focusing their efforts on catching females. If one slits
the belly of a gravid female, the egg mass is immediately evident
and often ‘boils’ out of the wound. A tightly patterned shotgun
wound has a similar effect. The locals eagerly and greedily col-
lect the egg masses, which are considered with some justification
to be special delicacies. The French traveler, Thébaur, during his
upcountry tour, made similar observations — and little has
changed today in southern Guahana or on Marajó.

“From September on, the females begin to leave the banks
of the large rivers, following the feeder creeks in order to pene-
trate farther into the lowlands. There they seek sandy places and
old dunes where they will hide their eggs in self-constructed
burrows, over which they are quite adept at smoothing the sur-
face sands and rendering the nest nearly invisible. A good eye
and considerable experience are necessary to find such places,
and the locals have developed astounding skills along these
lines. Once the females have completed their business, they
return to the banks of the rivers.

“The brood consists of 1–1 1/2, at most two dozen eggs,
figures that correspond with the numbers of follicles found in
the ovaries of females collected in August. I shall use as repre-
sentative examples, typical in size and shape, two well-devel-
oped eggs acquired from the Atlantic Coast of Marajó on 22
September 1886: 1. length 43 mm, breadth 26 1/2 mm, 2.
length 43 mm, breadth 26 mm. In form they are broadly ellip-
tical; the white shell is soft, and gives way to the slightest touch.
Nevertheless, it is tough, and penetration with a single cut is
possible only with a carefully sharpened knife.

“Iguana eggs are, as mentioned previously, delicacies. The
extensive, granular yolk is tasty. It never hardens completely
when boiled and can be spread like butter. Like those of the
Amazon River turtle (Podocnemis expansa), they are somewhat
hard to digest. Iguana meat also is quite tasty, and it reminds
me of that of the local armadillos. It serves as a nice change of
pace for river dwellers, and our museum personnel invariably
voice their approval if iguana, boiled or grilled, is served. Here
in Pará, one sees iguana meat offered for sale by the kilogram
in the market or along the streets.

“I don’t want to avoid reporting that finding food in our
gardens for our wild-caught captive iguanas was, at first, a dif-
ficult task, primarily due to the fact that the above-mentioned
plants have been displaced by civilizations throughout most of
the city and its immediate environs. After considerable search-
ing and experimentation, we were thrilled to find an excellent
surrogate in a weed, locally known as ‘malvarisco,’ which thrives

58 IGUANA  •  VOLUME 11, NUMBER 1  •  MARCH 2004 WERNER



IGUANA  •  VOLUME 11, NUMBER 1  •  MARCH 2004 59BIOGRAPHICAL SKETCH

Emílio Goeldi was a Swiss-born Brasilian naturalist. He stud-
ied at the University of Naples before earning his doctorate in

1883 at the University of Jena, where he studied under the famous
evolutionary biologist, Ernst Haeckel. Goeldi emigrated to Brasil
in 1884 to become assistant head of zoology at the Museu
Nacional in Rio de Janeiro. He lost that position as a consequence
of political changes, but, in 1894, accepted an invitation by the
governor of Pará, the large northern state at the mouth of the
Amazon River, to become Director of the Museu Paraense. Goeldi
served in that capacity until 1904, when he resigned for reasons
of health and returned to Switzerland. The museum was subse-
quently renamed the Museu Paraense Emílio Goeldi in his honor.
In 1908, he became Professor of Zoology at the University of
Bern, a position he held until his death.

Goeldi published in many areas. His most widely recog-
nized work was As Aves do Brasil (The Birds of Brasil), published
in 1894–1900, followed by an atlas in 1900–1906. Most of his
herpetological work dealt with classification and distribution, but
he also had a special interest in reproductive biology. Goeldi dis-
covered Hyla (now Flectonotus) goeldii (named by George A.
Boulenger in 1895), a frog in which the female carries the eggs
attached to her back. Goeldi’s major work in herpetology, Repteis
do Brasil, was completed in 1892–1894, but was never published
as a single volume. Much of the content consisted of compila-
tions from the literature, but many of Goeldi’s field notes (such
as those quoted here by Werner) also were included.

B I O G R A P H I C A L  S K E T C H

Emílio Augusto Goeldi 
(1859–1917)

Emílio Goeldi (photograph courtesy of Kraig Adler).

in fallow fields and orchards. Iguanas readily accepted its leaves,
which are similar in size to those of the coltsfoot. Since we have
been feeding Heckeria peltata, we’ve not lost a single iguana; just
the opposite, as a matter of fact, they are thriving and are, in
many instances, downright fat. They also have begun to exhibit
signs of becoming tame, moving toward the keeper when he
brings them food. We have in a small way endeavored to culti-
vate this plant, specifically for our iguanas. This is in every way
simple, and I am convinced that it would serve well as a crop
raised in greenhouses by zoological gardens. It grows rapidly
and is easily propagated from seeds. This weed requires no spe-
cial care, requiring little investment of effort or money.

“Iguana tuberculata [= Iguana iguana], called ‘cameleão’ by
natives, occurs in great numbers on Mexiana Island, but it is
not easy to find because its green color blends well with the tan-
gled bankside vines on which it prefers to perch. These iguanas
are shy and, once they take flight, literally shoot across the
crowns of trees and bushes with such alacrity that they disap-

pear almost immediately from the view of the hunter and can
be traced only by following the tell-tale crackling of small
branches broken during their effort to escape. They will ascend
the highest forest trees, and I recall one individual I shot down
from an astounding height.

“The nest cavities are typically dug at an angle, with an
approximately two-foot long passage leading to a slightly
enlarged cavity that serves as the egg depository. Because the
sand dunes are repeatedly watered during the rainy season, suf-
ficient moisture is retained to keep the sandy burrow from col-
lapsing. Consequently, these sites lend themselves to easy exca-
vation through loose sand, but retain the moisture necessary to
sustain the eggs. Although the nest cavities are carefully filled
by the females, fresh nests are easy to find, as no effort is made
to wipe out the telltale tracks. Because, however, the direction
of the sloped passage is not always evident, natives probe the
sand and identify the passage or even the egg chamber by the
lack of resistance to their efforts.”

Source: Adler, K. 1989. Herpetologists of the past, pp. 5–141. In K. Adler (ed.), Contributions to the History of Herpetology. Society
for the Study of Amphibians and Reptiles, Contributions to Herpetology, Number 5. Ithaca, New York.


