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IGUANA  •  VOLUME 11, NUMBER 3  •  SEPTEMBER 2004 179HISTORICAL PERSPECTIVES

The following observations on the iguana were made during
a two year stay in Panama: in the tropical forest vicinity of

Pacora, in the sabanas around La Chorrera and in the various
habitats found within the Canal Zone.

Terminology
The name iguana is the only one that I have heard used for this
lizard by English speaking people, with the exception of show
people in the United States who sometimes use more spectacu-
lar terms, such as “dragon.” In Central America the Spanish-
speaking people usually call the female iguana and the male gor-
robo. The male is sometimes called ministro in El Salvador, and
guacho in Costa Rica. The young, of course, is called iguanita or
gorrobito. In Panama the lizard is facetiously called gallina de palo,
“chicken of the tree.” Most Americans consider any small lizards
in the tropics iguanas, ameivas and basilisks in particular, just as
they call almost any tree a mahogany tree.

Sexual Dimorphism
Males of this species show quite a variety of color; their heads vary
from whitish, grayish, pinkish, to orange and black. The males
in general have more orange and yellow coloring than the
females, which are lighter colored and more greenish. Females are
usually smaller than males of the same age, and the head is
smaller in proportion to the body. The dorsal spines are shorter
in the female, being from one-half to one inch in length, while
those of the male are two inches or more. The male has a row of
glands on the underside of each thigh. Externally they appear as
disc-shaped, warty excrescences; just beneath the skin they are
spherical in shape and measure from four to six millimeters in
diameter. One male had 17 on one leg, 18 on the other.

There is a belief in El Salvador that these glands are warts.
It is believed that a person can get warts from the blood of an
iguana, unless it is washed off before it becomes dry. I have asked
Salvadoreans why warts were common in the United States,
where there are no iguanas. I was told that they could be acquired
from inadvertently coming in contact with urine from a person
having warts. When I asked how they explained the fact that chil-
dren had warts more commonly than adults, I was told that they
were transmitted through the mother. When told about the myth
prevalent in the United States, that handling toads caused warts,
they were not familiar with this belief, and denied vehemently
that toads would cause warts.

Male iguanas either outnumber the females, in adults, or are
more conspicuous in their habits. On one trip I collected seven
males to one female. Possibly among the older population, more
males survive predators than the smaller females.

Habitat
The iguana is quite arboreal in its habits, but it is also at home
on the ground. It is an excellent swimmer and takes voluntarily
to the water to escape its enemies. I have never observed adults
very far away from trees, although the young will wander quite a
distance from them. They are particularly numerous in trees
overhanging rivers, or perhaps they are more easily observed from
the water. During cold, wet weather, they seem to prefer to stay
on the ground, probably for greater warmth afforded by ground
cover, such as brush, hollow logs, holes, etc. On one collecting
trip, after a prolonged cool and wet period, I observed no igua-
nas in the trees. Then the sun came out, and as it rapidly warmed
up, iguanas were noticed coming to the tops of bushes and
ascending into the tops of trees. In favorable weather, they appar-
ently spend most of the time in the trees and even sleep there
overnight.

I once watched an old male, in a big fig tree near Gatun, for
several days. The tree was more or less isolated from others, and
as the iguana had an unusual reddish color to its head, I felt rea-
sonably sure that it was the same specimen. I could see him from
quite a distance, but when I came beneath the tree, he tried to
keep a branch between us. I first noticed him on September 20.
On the 21st I was working in the same locality and observed him
every time I looked for him, from 7:30 a.m. until 2:15 p.m.,
when I left. On the 22nd I couldn’t locate him. On the 23rd I saw
him at 8 a.m. That day, while I was away eating my lunch, some
of the men in my crew of laborers entertained themselves by
catching this iguana for me. They had not known that I was
watching it, and thought I’d be pleased with it.

Another large male was conspicuous in a big ceiba tree at
Fort Davis. It was late in November, and the tree was bare of
leaves. The new leaves were coming out and the iguana was feed-
ing on the new shoots. This lizard remained in the same tree for
at least four days.

Their choice of trees is based mostly on the food available at
the time, as they probably select the species according to the sea-
son of new shoots, flowers, fruit or leaves. Apart from the feed-
ing angle, they seem to prefer heavily foliaged trees when the sun
is bright, and when it is raining, more open trees are preferred,
such as the wild fig. Species to which they seem particularly par-
tial are the wild plums, Spondias species; the palo bobo, Erythrina
glauca; the guacimo, Luehea seemannii; the wild cashew, Espave

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

The Iguana 
Iguana iguana iguana (L)1

Paul L. Swanson

1 Originally published in Herpetologica 6:187–193 (1950).
Reprinted with permission. Bracketed names were added and one
typographical error corrected.



180 IGUANA  •  VOLUME 11, NUMBER 3  •  SEPTEMBER 2004 SWANSON

excelsum, to mention a few. They are liable to be found on almost
any tree, however, even small species like the Cecropias.

I once saw two iguanas we had shaken from a tree run into
an armadillo hole to escape capture. When frightened from a tree
growing on the bank of a river, they prefer to jump into the water
rather than on land. They usually swim under water and come
up under brush along the shore line, if such is available. A jump
from a tall tree doesn’t seem to hurt them. I’ve seen them leap
from heights of forty or fifty feet and apparently land unhurt.
Some times their tail is broken by intervening branches, or brush,
but even if they hit practically bare ground, it takes a “flying
tackle” at the moment of contact to capture one before it runs
away.

Very young iguanas are frequently seen on the ground,
sometimes in open areas, and they are probably terrestrial to a
large degree. I have never seen one under ten or twelve inches in
a tree, although smaller lizards would naturally be more difficult
to observe there than on the ground. (I have observed many small
lizards of other species in trees, however).

Locomotion
Iguanas are very agile climbers. I once observed a specimen climb
the underside of a fairly large and smooth limb. They attempt to
keep a limb between them and an observer, in the manner of  a
squirrel. Sometimes they will go from one tree to another, if the
branches are interlaced, and I have seen them make short jumps
from one tree to another. In leaping to the ground or to the water

from a tall tree, they hold the legs closely to the body in flight. I
have not been able to verify how they break their fall, but it
would seem that they would have to extend the legs, and that
they might use the tail to some extent. While the tail isn’t so brit-
tle as that of most lizards, one frequently captures specimens with
part of the tail regenerated.

At rest in a tree, they sometimes sprawl out parallel to a limb
with the hind legs dangling over into space, not even the claws
being in contact with the limb.

In swimming, an iguana lets its four legs hang limply against
its side, and propels itself with powerful strokes of the tail, much
like a crocodilian. I have never seen one swim on the surface; they
were always submerged.

Once I released an iguana on an open grassy area. At first it
wouldn’t try to run away, so I left it for about an hour, and when
I returned it had started to walk. When it saw me, it began to
run, but I overtook it easily, when it again became quiescent.
Although this specimen traveled not more than seven miles per
hour, I believe that an undisturbed adult could probably attain a
speed of ten or twelve miles per hour for a short distance.

Food Habits
One of the favorite foods of the iguana in Panama is the wild
plum, Spondias mombin. The fruit is about 1 1/4 to 1 1/2 inches
in length, by about 3/4 inch in diameter, shaped somewhat like
a prune, and containing a large pit. It ripens over a long period
in August and September. Of seven iguanas I dissected on

A Central American Green Iguana (Iguana iguana). Photograph by Robert W. Henderson.



IGUANA  •  VOLUME 11, NUMBER 3  •  SEPTEMBER 2004 181HISTORICAL PERSPECTIVES

September 2 (1943), five of them contained plums: 16, 29, 39,
41 and 79, respectively. The one with 16 plums also had many
leaves in its stomach, the others very few. One other contained
leaves and seeds of the guacimo tree. The only female of the seven
contained no plums and only a few leaves, but a great many
seeds, which my woodsmen identified as fig seeds, although one
of them disagreed and insisted that they were seeds of the canillo,
Miconia argentea.

Other iguanas dissected contained fruit of the pepenance,
Ximenia americana, and mango leaves. I have observed them eat-
ing the leaves of the morning glory, Ipomoea species, and new
shoots of the ceiba, Ceiba pentandra. They undoubtedly eat many
different species of leaves, blossoms, buds and fruit. Native
Panamanians and Salvadoreans claim that they frequently eat
leaves from vegetables in gardens. Several natives claimed that
they had seen iguanas, not once, but a number of times, eat
human excrement. In captivity I have had them eat ripe bananas.

Very young iguanas are probably almost entirely insectivo-
rous2, but I have made no personal observations on their feeding
habits. I find no mention of stomach stones in my notes, nor do
I remember finding any.

Mating
I have not observed iguanas in the act of mating. One of my
workers saw a pair mating in El Salvador. If he remembered cor-
rectly it was in October. They were closely intertwined and upon
the ground. Another claimed that they mated in November at
the close of the winter (rainy season). It is very likely that mating
takes place upon the ground; if it took place in trees it would be
more often observed. Many of my men were excellent woodsmen
and observers of nature, but few had ever seen iguanas mating.

Egg Laying
The eggs are laid from early February to March. They are spher-
ical in shape and have a white shell, about 30 mm. in diameter.
One informant told me that they are laid on the ground and cov-
ered with dirt. They probably hatch in about three months.
(Young iguanas are commonly seen from June on). The number
deposited varies greatly; there may be as few as twenty or as many
as seventy. A specimen dissected on a September 26 contained 72
eggs, varying from 3 to 6 mm in diameter; the total number
probably represented more than one clutch. Another examined
on a November 21 contained 28 large eggs, of about 15 mm. in
diameter, and many that were much smaller. Late in January the
eggs are about 25 mm. in diameter.

Growth
Young iguanas are observed most often in June and July. A native
observer said that they reached a length of about three feet at the
end of their first year. This sounds reasonable, as in June or July
most specimens seem to be under ten inches or over three feet in
length. They probably attain full size in two years. Older speci-
mens seem to become thicker in build but do not grow much in

length. A specimen five feet in total length, and weighing about
ten pounds, may be considered large. The largest specimen of
many hundreds that came to my attention was caught at Fort
Gulick, Canal Zone. It weighed 13 1/4 pounds, and measured
66 1/2 inches in total length, 4 inches of the tail having been
regenerated. With a normal tail it would not have been more
than an inch or two longer. The snout to vent length was 20 1/4
inches. I have not seen wild ones (at large) that I thought were
any larger than this specimen.

Frequency
Iguanas are very common in many places where they occur. In a
hunt for them near Margarita, Canal Zone, on a September 26,
I personally observed 39 specimens in two hours; of these my five
helpers caught 8. They undoubtedly saw many more that I did
not. That afternoon I observed 20 more, although I was not
hunting for them then.

Between Margarita and Gatun, while driving slowly along
the road one morning shortly after sunrise, I counted 58 iguanas
sunning themselves on the tops of trees, within a distance of three
miles. It is not unusual to see four or five in a tree. We once
routed 12 iguanas from one fig tree, Ficus glabrata.

Enemies
Many iguanas are marked by bad scars. According to the natives,
most of the scars are the result of attacks by hawks. I have no rea-
son to doubt this, as hawks are very numerous in the tropics, and
the iguana’s habit of basking in the tops of tall trees would make
it very logical prey. The fear of hawks is the basis of a stratagem
for catching iguanas. The native whistles or screams like a hawk,
which “freezes” the lizard and makes it easier to capture. I can not
vouch for this personally, but I do not discredit it, as when fright-
ened badly enough, an iguana usually remains motionless.

Boas and other snakes undoubtedly eat many iguanas. Small
snakes are capable of eating young specimens. We once caught a
boa, Constrictor c. imperator [= Boa constrictor] of only six feet in
length that contained an adult iguana. It was a big meal for the
snake, and the tremendous bulge it made in his body rendered
the capture of the snake very easy. I have no records of predatory
mammals attacking iguanas, although I see no reason why they
should not.

Defense
The iguana’s chief defense against its enemies is probably its abil-
ity to climb, run, and swim. Its protective coloration is an aid in
escaping the notice of many potential enemies. It is amazing how
inconspicuous it can be. I have talked to people who have lived
in the Canal Zone for two or three years without having noticed
a wild iguana, although they are present in large numbers in
many parts of the Zone. Once when on a hunt, five good
campesinos and myself could observe but three iguanas in a
guacimo tree. A couple of the boys climbed it, and frightened ten
iguanas to the ground.

Their keen vision helps them to avoid enemies. On an open
sabana, one gave evidence of having seen me while I was still 100
yards away. I have tried to approach them in trees close enough
to photograph, but could seldom get within 25 feet of one before
it would leap to the ground.

2 Editors’ note: Green Iguanas of any age are herbivorous. Accounts
of insectivory are due to incidents induced in captivity and should
not be used to justify feeding meat or insects to captive Green
Iguanas.



Usually a captured specimen offers no resistance. If it is
released and teased, it sometimes puts up quite a show of angry
defense. Some of my men once caught and released an iguana,
unknown to me. I came upon it, thinking it a wild one, and
when I got close enough, it lashed out with its tail, striking me
on the side of my thigh between the knee and hip. It raised a welt
which lasted several hours. It also threatened to bite. I took it into
a cabin and thrust a broom at it. The lizard struck at the broom
with his tail, then bit at it savagely, taking off part of the straw.
Another specimen, trussed up in the usual Panamanian manner,
managed to get its front legs loose and bruised one of my com-
panions arms with its tail. Wounded specimens are much more
likely to fight than uninjured ones. Some natives claim they can
make a good account of themselves with a small dog.

Commercial Value3

Iguanas are a source of meat for a great many tropical American
people. Their use as food seems to be confined to the areas where
they are indigenous, as they are seldom transported from the low-
land tropics to the cities at higher elevations where the iguana does
not occur. Most natives of Central America who live where igua-
nas occur consider them excellent food. The Jamaican negroes
who worked for me in the Canal Zone could hardly conceal their
disgust at people eating lizards. Some of the highlanders of Central
America feel the same way. Personally, I think they are delicious.

Unlike most animals, old specimens are better eating than
young ones, perhaps because they are not so agile, resulting in
softer muscles than in young, active specimens. Their diet prob-
ably affects the taste also, as younger individuals may not have
completely overcome the insectivorous habits of their infancy.
Possibly when feeding on fruits they have a better flavor than
when feeding on leaves and other vegetation that would impart
a flavor less palatable to humans. In the dry season they are not
as good eating as in the rainy season. One I cooked for three
hours in July remained tough and not very tasty. Just after egg
laying, in March, to about July, they are at their worst. They are
usually considered at their best in September and October. Many

writers have mentioned tasting the flesh of the iguana and find-
ing it unpalatable. In such cases, they have either let their imag-
ination get the best of them, have tasted them at the wrong sea-
son or have tried too young a specimen. I have eaten many of
them and find them delicious — equal if not superior to chicken.

Their eggs are also considered a delicacy. I have eaten them
taken from an iguana and boiled. To me they tasted much the
same as the hard boiled yolk of a hen’s egg, and had much the
same appearance. The natives also eat them dried, as sort of a
confection.

The market value of iguanas varies much from country to
country. In Panama, in 1943, at the market in Panama City, a
large female with eggs sold for about $2.00 (males slightly
cheaper). At the same time, the best class of fish retailed for about
32 cents per pound; chickens 60 cents live weight and 70 cents
dressed. Such an iguana would weigh 8 to 10 pounds. Turtle
steaks were 30 cents per pound.

In El Salvador at the same time, a similar iguana sold for the
equivalent of 30 cents to 40 cents U.S. In Nicaragua they could
be bought for as little as 15 cents U.S.

Eggs of the iguana sold in Panama City at 7 for 10c and in
Cartagena for as little as 4 for 1c U.S. In Barranquilla, a string of
50 was sold for about 25c U.S.

The iguana is a particularly convenient source of meat in hot
places, as it can be kept alive for a long period without food or
water. In Panama it is the custom to fold the legs over the back,
securing them by slitting the skin of the toes and placing a claw
of one foot through the tendons of the toes of the opposite foot,
and twisting them. This renders the iguana helpless. In Panama
City one may see dozens of them lying in the street of the mar-
ket place. I am told that in Venezuela the natives simply break
the iguana’s back to keep it more or less immobile.

I do not recall having heard an iguana voice a sound of any
kind. However some of the mestizos who worked for me told me
of an occasion in which an iguana caused much excitement
among the sight seers who flocked off a boat at Cristobal. The
big lizard, held by a Panamanian, made lots of peculiar noises,
whistled and “talked.” An excited gringo thought that he had
made a wonderful discovery for some zoo, and convinced the
Panamanian to part with it for the measly sum of $10.00. Of
course it was a trick of ventriloquy.

182 IGUANA  •  VOLUME 11, NUMBER 3  •  SEPTEMBER 2004 SWANSON

3 See also “A backward glance at iguana exploitation” (IGUANA
10(3):63–66).

Green Iguanas still appear regularly at Central American markets. Photographs by Gunther Köhler.


