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G
reen Iguanas (Iguana iguana) are inap-
propriate pets. Like monkeys, raccoons,
and skunks, they are cute and tractable
as juveniles but become difficult to man-

age as they grow. Most captives suffer one of two
fates. Either their needs are poorly met and they
die at a young age, or they grow into large, active,
aggressive adults for which few keepers can pro-
vide. Reptile adoption and rescue agencies are
overwhelmed with unwanted iguanas. Successful
iguana owners, those experienced in iguana care
and behavior, are among the first to suggest that
this species is a poor choice for all but the most
dedicated keepers.

In choosing a pet, people select reptiles in gen-
eral, or iguanas specifically, for a variety of reasons.
A small group of keepers has a strong, sincere
interest in herpetology and iguanas in particular.
These people make the best keepers, and are
always reading, researching, and trying to improve
their knowledge and level of care. A bigger group
of keepers uses the reptile to satisfy the basic
human need to be unique and stand out: “Look at
me, I have a weird pet.” Many exotic pets are cho-
sen for this reason, and these owners often take
shortcuts in providing care because the animal
itself is not as important as having it. Still others
choose a reptile because they are non-allergenic,
low-maintenance pets that can be left unattended
for days at a time, and convenience outweighs
dedication. The final group of keepers incorporates
the impulse buyers who see an interesting, inex-
pensive lizard in the pet store and buy it with little
regard for its captive requirements. These people

succumb to what Dr. Doug Mader calls the
iguana’s high “cool” factor.

Whatever the reason a reptile is chosen as a
pet, iguanas are one of the more popular reptiles
because they are inexpensive and readily available.
Moreover, they are vegetarian and, in this age of
animal rights, many owners prefer not to deal
with insect or rodent prey. The down side, of
course, is that vegetarian diets are much more dif-
ficult to balance than are insectivorous or carniv-
orous diets.

Like Pot-bellied Pigs, hedgehogs, and imported
adult Ball Pythons before them, the Green Iguana
fad is on the down slope of its bell-shaped curve of
popularity when compared to the 1990s. The word

129IGUANADecember 2003

1 This feature was adapted from an article of the same title
presented as part of the Bayer Exotics Symposium in 2002
(Suppl. Compend. Contin. Educ. Pract. Vet. 24:13–22).
Portions of that and this manuscript are based on Barten,
S.L. In Press. Biology: Lizards. In: D.R. Mader (ed.), Reptile
Medicine and Surgery. 2nd ed. W.B. Saunders, Inc.,
Philadelphia, Pennsylvania. Used with permission of the
Bayer Corporation and Bayer AG Leverkusen.

A healthy female Green Iguana (Iguana iguana).
Photograph by Tom Wiewandt.

Green Iguana 
Management and Husbandry1

Stephen L. Barten, DVM
Vernon Hills Animal Hospital, Mundelein, IL 60060

H U S B A N D R Y



is seemingly getting around that these are difficult
captives. Nevertheless, a core of dedicated keepers
will always be seeking veterinary advice.

One of the biggest problems of keeping
iguanas — or any reptile — in captivity is that no
standard of care has been established for them.
Indeed, any internet search using the key words
“iguanas, pets, and husbandry” (or “care in cap-
tivity”) will turn up an astonishing number of per-
sonal web pages for individual pet iguanas which
are laden with advice, often conflicting, on captive
care. Recommendations for captive care are almost
universally based on anecdotal or personal experi-
ence with a few specimens rather than scientific
research. Instead, captive care should be based on
the biology and natural history of iguanas in the
wild. The more their conditions mirror what they
evolved to utilize in nature, the healthier captive
iguanas will be.

Natural History
Few reptiles have been studied as extensively as

have Green Iguanas. This very brief summary of
their biology is an overview meant to illustrate
applications to captive management. Green
Iguanas inhabit the New World tropics and sub-
tropics from northern Mexico to Paraguay and
southeastern Brazil, along with many Caribbean
islands. Iguanas are diurnal and arboreal, prefer-
ring tree tops along rivers, lakes, and mangrove
swamps. Trees provide an abundance of sun and
shade for thermoregulation and basking, as well as
food and sleeping perches. Iguanas sporadically
descend to move to other trees, avoid threats or
nest. An iguana may stay in one tree for anywhere
from one day to several weeks. Iguanas also utilize
more open, arid habitats if sufficient food
resources are available.

The home range of a reptile is that area uti-
lized for acquiring or accessing necessary resources
such as food, shelter, basking sites, escape routes,
mates, and nesting sites. Home ranges are not
defended against conspecifics and ranges of indi-
viduals typically overlap. Territory is that subpor-
tion of the home range that is defended from con-
specifics or other species, usually because it
contains a critical resource. For iguanas living in
trees, food is abundant and the main defendable
resource is reproductive females. The measure-
ment of home ranges for arboreal species is diffi-
cult because it is three-dimensional and contains
gaps of unusable areas. Nevertheless, one study

reported mean home ranges for iguanas observed
at least three times over a minimum of two
months. Large males occupied 800 m2, medium
and small males covered 2,200 m2, and females
ranged over 2,450 m2. Another study showed
mean daily movement totals of 111 m for male
and 135 m for female iguanas. Flight distances of
iguanas in trees (the distance at which the
approach of a threat caused the lizard to flee) was
50–60 m after basking and 90 m before basking.

Iguanas are one of few totally herbivorous
lizards. They are joined by many of the other
New World Iguaninae, the spiny-tailed agamid
Uromastyx spp., Sailfin Dragons (Hydrosaurus
spp.), Fiji Island Iguanas (Brachylophus spp.), and
the Solomon Island Skink (Corucia zebrata).
Suggestions that iguanas undergo an ontogenetic
shift from insectivory to herbivory are based on
observations of captives and anecdotal field
observations and are incorrect. Iguanas spend
90–96% of their time resting and only 1% eating.
Daily forage times last only 20–30 min. Iguanas

130 IGUANA Volume 10, Number 4

Tropical rain forest in Costa Rica. Green Iguanas were abun-
dant and dozens and dozens of adult lizards were seen.



generally eat the leaves of trees and vines. Analysis
of stomach contents from 31 iguanas in Panama
revealed only plant material comprising 26 plant
species. Twenty-four stomachs contained only
leaves, four contained leaves and flowers, two
only fruit, and one only flowers. Iguana teeth
work like pinking shears and cut out sections of
leaves, but iguanas do not masticate before swal-
lowing. All herbivorous lizards have an enlarged
colon divided into compartments by circular and
semilunar valves composed of infolded mucous
membrane, submucosa, and the internal muscu-
laris externa. The number of valves varies by
species and Green Iguanas usually have 6 (5–7,
but only four in populations from the northern
Lesser Antilles). Their function may be to slow
gastrointestinal transit time, increase surface area,
or provide habitat for commensal microbe and

nematode populations. Wild herbivorous lizards
typically have huge oxyurid (intestinal round-
worms) burdens of up to 15,000 worms per
lizard. These are not found in other lizard
species. The nematodes may serve to mechani-
cally mix and break down plant material, produce
useable cellulase, vitamins and fatty acids, or pro-
mote healthy populations of fermentative
microbes in the colon. Nevertheless, dewormed
lizards had efficient digestion, so nematodes,
although common, may be relatively unimpor-
tant. Thirty to 40% of nutritional energy derives
from microbial fermentation in the hindgut. This
process requires high temperatures and slow pas-
sage times, averaging 6.9 days in wild iguanas in
Venezuela. Wild neonate iguanas inoculate them-
selves with fermentative bacteria by ingesting the
feces of adult iguanas after hatching.

131IGUANADecember 2003

Iguanas are arboreal and
prefer trees along rivers, lakes
and mangrove swamps (A).
This river was in Costa Rica.
The speck on the branch of
this tree is a large Green
Iguana (B). Basking high in
the top of a tree is typical
iguana behavior, and serves
as proof that most captive
iguanas are kept in inade-
quately small cages.

A

B



Thermal ecology of reptiles is complex. The
term “Preferred Optimum Temperature Zone” is
common in the veterinary literature, but ther-
moregulation in ectotherms involves much more
than that. The “Preferred Temperature” is the
temperature selected by lizards in a thermal gradi-
ent when not distracted by other influences, like
shelter. The “Mean Activity Temperature” is the
mean temperature of all active lizards. The
“Activity Temperature Range” is the range in
which activity occurs. The “Voluntary Minimum
and Maximum” are the lowest and highest tem-
peratures tolerated in laboratory conditions, and
these define the endpoints of the Activity
Temperature Range. The “Critical Thermal
Minimum and Maximum” are the extreme tem-
peratures that result in immobility and death.

Voluntary minimum, maximum, and mean tem-
peratures for Iguanidae were reported as 18.0°,
46.4°, and 36.7° C (64.4°, 115.5°, and 98° F),
respectively. Circadian temperature fluctuations
(low at night and high during the day) within the
activity temperature range are very important, and
lizards kept at uniform temperatures 24 hours a
day fail to thrive.

Iguanas appear to have high requirements
for ultraviolet light for vitamin D and calcium
metabolism, although specific wavelengths,
intensities, and photoperiods have not been
quantified. Nonbreeding iguanas in Venezuela
basked for approximately 4 h in the morning
and another 2–3 h in the afternoon. Basking
provides for thermoregulatory as well as ultravi-
olet needs.

132 IGUANA Volume 10, Number 4

Adaptations for herbivory in
Green Iguanas. (A) Iguanas
have homodont (all the same
shape), pleurodont (frequently
shed and replaced) teeth
designed for cutting large
pieces of leaves, which are
then swallowed relatively
whole with little chewing. The
points of the teeth interdigi-
tate to cut leaves like pinking
shears. (B) Dorsoventral
radiograph of an iguana. The
colon is silhouetted by air
density in the lung. The
semilunar valves that divide
the colon into compartments,
which are typical of herbivo-
rous lizards, are outlined and
made visible by ingesta.

A

B



Iguanas communicate primarily through visual
signals. Dominant males exhibit physical charac-
teristics that emphasize their size, such as large
heads, opercular scales, crests, spines, and dewlaps,
and sometimes orange skin coloration. Likewise,
head bobs, pushups, throat expansions, and
dewlap erection are used to convey threat. Threats
may escalate to lunging, biting, and tail slapping,
although, in the wild, displaying males tend to be
well spaced so that displays outnumber actual
fights. Chemical and tactile signals are less impor-
tant; however, femoral pores are well developed in
males and produce secretions that provide both
chemical and visual cues. The femoral pore secre-
tions of Desert Iguanas (Dipsosaurus dorsalis)
reflect UV light in wavelengths that are visible to
the lizards but not to humans.

Breeding is seasonal and associated with the dry
season. Males display on perches and defend terri-
tories from November through January, becoming
very aggressive toward intruding males. This corre-
sponds to a seasonal testicular recrudescence, dur-
ing which the testicles undergo marked enlarge-

ment and testosterone production peaks. Breeding
behavior is characterized by dominant male hierar-
chies utilizing small mating territories, intense com-
petition between males, and female mate selection
determined by male fitness. Females nest 3–7 weeks
after breeding, produce clutches ranging from
14–76 eggs (average 35–43), and eggs hatch after
10–14 weeks of incubation at 28–32° C. Iguanas
often nest communally due to limited numbers of
available sites, excavating nest sites at the bottom of
burrows 1–2 m long and 0.25–0.5 m deep. Females
guard nests from other females.

Nonbreeding iguanas are more tolerant of the
presence of other iguanas and do not defend terri-
tories. Low-intensity antagonistic interactions
occurred when two iguanas passed on a branch
but ceased after they separated. Nonbreeding
females occupy prime basking and sleeping perches
and chase away new females.

Husbandry
The conditions iguanas require and utilize in

the wild obviously cannot be provided in captivity.

133IGUANADecember 2003

A very large, male, sedated Green Iguana. Size and dominance are communicated through visual cues. Note the large head,
large opercular scale on the jowl, large dewlap, and tall dorsal spines. This iguana was caught as a feral animal in Florida,
where it was thriving outdoors. The right front foot and forearm are swollen as a result of a bite wound from another
iguana. Several iguanas including territorial males were housed together due to lack of space at an animal dealer’s facilities.



No iguana husbandry can be described as
“proper,” and captive conditions always have room
for improvement. Captive iguanas tolerate less than
ideal conditions, nevertheless keepers must be
aware of iguana natural history and make every
effort to provide for their needs. These needs
include large, three-dimensional home ranges, focal
heat sources approaching 36.7° C (98° F), strong
UV sources, a balanced vegetarian diet, and avoid-
ance of the various levels of aggressive and antago-
nistic behavior between individuals. Every captive
iguana is under some degree of chronic stress just
from being in captivity. Conditions that are well-
tolerated by one lizard may cause serious problems
in another, and keepers must be flexible in their
techniques according to their results. Captive man-
agement should be investigated and improved for
any iguana presented to a veterinarian for any rea-
son, without exception.

Iguana husbandry has been the subject of
innumerable books and magazine articles. To cover
the topic in depth here would be to reinvent the
wheel, and such a complex subject cannot be dis-
cussed in detail in this limited space. Veterinarians
and owners alike should be thoroughly familiar
with one or more of the three best books on iguana
husbandry: Kaplan’s Iguanas for Dummies,
Hatfield’s Green Iguana: The Ultimate Owner’s
Manual, and Rosenthal’s The Iguana: An Owner’s
Guide to a Happy Healthy Pet. Melissa Kaplan is
considered a leading authority on captive iguana
management and, in addition to her excellent
book, she maintains the Melissa Kaplan’s Herp
Care Collection web site at www.anapsid.org. This
is one of the finest web sites on herp care because
it is comprehensive, current, accurate, well-refer-
enced, and frequently updated.

Two main schools dominate captive reptile
husbandry. Traditionally, bare cages with newspa-
per substrate and a single branch and water bowl
were recommended and popular. Ease of mainte-
nance was achieved at the cost of stimulation and
enrichment for the iguana. Lately, complex, natu-
ralistic vivaria have become fashionable. Such cages
are aesthetically pleasing, but also labor-intensive to
maintain, and few but the most dedicated and
experienced hobbyists do an adequate job of sus-
taining hygiene in complex cages. If a keeper can-
not properly maintain a complex vivarium, then a
simpler setup would be a better choice. Likewise,
ingestion of substrate is common when gravel or
bark is used, especially if the diet is unbalanced or

inadequate in amount. In spite of the potential
problems, cages should be enriched to reduce stress
and allow normal behaviors among inhabitants.

Caging.—Iguanas are arboreal lizards that
require huge cages to accommodate their active
behavior, and most keepers provide cages that are
too small. One expert recommends a cage length
equal 1.5–2 times the total length of the lizard
housed within, and a cage width at least half that
distance. Another expert suggests even more
space, 0.4 m3 cage space per 0.1 m total length for
arboreal lizards. These are suggestions only and
come nowhere near providing the space that wild
iguanas utilize, with home ranges measuring over
2,000 m2 (a square measuring 146 ft per side) and
daily movements exceeding 100 m (328 ft). With
that in mind, iguanas should be provided the
biggest possible cages with the goal for adult
lizards of at least 10 x 3 by 6 ft high, although a
room-sized enclosure would be better. Anything
smaller would be the equivalent of a human living
in a telephone booth: possible, but hardly humane.
Aquaria sold for juvenile iguanas will be outgrown
in a few months, and the need for custom cages
should be anticipated from the beginning.
Outdoor aviary-style cages with shelters from the
sun and inclement weather are strongly recom-
mended in warm climates or during the summer
months.

Cage sides should be smooth to prevent ros-
tral abrasions. Metal screening should be used with
caution, since it doesn’t retain heat and can result
in foot and rostral trauma. Plastic mesh, polyeth-
ylene hardware cloth, and plastic-coated wire mesh
are less abrasive. Cages made of wood must be
sealed with polyurethane, marine epoxy paint, or a
similar waterproofing agent, and joints should be
caulked to allow cleaning and disinfection.
Ventilation is crucial, as ample air exchange is nec-
essary to prevent the harmful buildup of bacteria
and fungi.

Lizards allowed to roam free in the house may
suffer suboptimal temperatures from the lack of a
heat source or exposure to cold outside walls and
windows or drafty floors. Trauma is common in
free-roaming iguanas that may be trampled, closed
in doors, fall from high shelves or curtains, or be
attacked by dogs and cats. Uncaged iguanas com-
monly escape.

Arboreal species require vertical space and
climbing branches. Dry climbing branches approx-
imately the same diameter as the lizard’s body

134 IGUANA Volume 10, Number 4



should be placed diagonally in the cage and
anchored to prevent toppling. Live, non-toxic
plants that lack spines and slippery surfaces and are
big enough to bear the weight of the lizard are
recommended. Dracaena and Ficus trees with
trunks as thick as the lizard’s body work well for
iguanas. These act as cage furniture, add humidity,
shelter, and visual enhancement. They should be
potted to facilitate cleaning. Silk plants may be
coated with toxic, water-soluble stiffeners and
should not be used.

Substrate.—Substrate can be flat newspaper,
indoor/outdoor carpet, orchid or so-called “rep-
tile” bark chips, alfalfa pellets, cyprus mulch, or
commercial animal bedding made from recycled
paper or wood pulp. Newspaper is inexpensive,
clean, and easy to use, but not aesthetically pleas-
ing. Carpet is labor-intensive, requiring washing.
Alfalfa pellets are digestible if ingested and look
nice, but are dusty and foul smelling when they get
wet. Orchid or “reptile” bark products made from
fir may be used, but never redwood or cedar. If
bark chips are excessively dusty, they should be
rinsed and dried before use. Coarse-grade bark can
irritate the feet of lizards that dig repeatedly and
fine-grade bark can cause fatal gastrointestinal
impaction if swallowed. With the current popular-
ity of naturalistic vivaria, many keepers feel the
advantages of bark outweigh these risks. A shallow
feeding dish can be used to minimize the risk of
accidental substrate ingestion, but the bark should
be removed if a keeper sees the lizard eat some or

finds it in droppings. Recycled paper animal bed-
ding currently is a popular substrate to use because
it is more absorbent and less dusty than alfalfa pel-
lets; it can be changed less frequently and it is
more or less digestible if swallowed.

Cedar shavings contain aromatic resins that
may be toxic to reptiles. Other substrates to avoid
include gravel, sand, crushed corn cob, clay kitty
litter, and miscellaneous wood shavings.

Thermoregulation.—Reptiles are ectother-
mic and require supplemental heat in captivity.
Temperatures within the Activity Temperature
Range are necessary to optimize metabolic
processes including digestion, growth, healing,
reproduction, and immune system function. The
Mean Activity Temperature (Tb, body tempera-
ture) for Iguanidae is reportedly 36.7° C (98° F);
consequently, a focal hot spot reaching this level
must be provided. Iguanas also are heliothermic
(gain heat by basking) and not thigmothermic
(gain heat by conduction from lying on warm
rocks), thus overhead heat sources are preferred to
substrate heaters. So-called hot rocks are com-
monly sold by pet stores for use with pet reptiles,
but are inappropriate for this species. Substrate
heaters under the tank may be used to provide
background heat in cold climates, but not primary
basking heat.

Reptiles in the wild control their core body
temperature to within a few degrees of their mean
activity temperature by thermoregulation — they
move all or parts of their bodies into or out of

135IGUANADecember 2003

A Bahamian Ground
Iguana (Cyclura cychlura
figginisi) in a huge outdoor
enclosure. Although not a
Green Iguana, the
principles are the same.
About one eighth of the
cage is visible here. It is
located under a tree,
providing both sun and
shade. Note the ramp
behind the lizard which
leads to a heated enclo-
sure to provide shelter on
cool nights. Note, too, that
the concrete walls are
buried in the ground to
prevent the lizards from
burrowing underneath
them. Photograph by
Juliann Sweet.



direct sunlight. Keepers should create a thermally
complex environment for captive reptiles to allow
them to adjust their body temperature behav-
iorally as they would in the wild. A thermal gradi-
ent on both a horizontal and vertical axis is ideal.
This can be achieved by providing a focal hot spot
on one side of the cage, covering less than 25% of
the cage, using overhead lamps with reflectors,
infrared ceramic heating elements, or radiant heat
panels. These must be secured to prevent them
from being tipped over or burning the lizard.
Heat sources should be attached to thermostats to
prevent accidental overheating, and a number of
commercial models are available specifically for
use with captive reptile enclosures. Fire safety pre-
cautions and smoke alarms should be used.
However, maintaining the entire cage at a uni-
form temperature would be unnatural. Diurnal
temperature fluctuations between day and night
occur in the wild, so heat lamps should not be left
on 24 h/day. Daily fluctuations in temperature
seem to be important for lizards. Nighttime tem-
peratures can approach the voluntary minimum
temperature for iguanas (18.0°C, 64.4°F), but
should not reach it to avoid stress and immuno-
suppression. Nighttime lows around 22°C (72°F)
are well-tolerated as long as adequate daytime
highs are provided.

The temperatures at both the hottest and
coldest parts of the enclosure must be measured
daily. Digital thermometer-hygrometers are useful.
Likewise, infrared thermometers that instantly
measure the surface temperature of objects from a
distance are highly recommended. Both are avail-
able from electronics stores and reptile supply deal-
ers. Adhesive aquarium thermometers stuck to the
side of the cage are not recommended, because
the temperature of the basking site where the rep-
tile rests should be measured rather than the tem-
perature on the side of the cage.

Osmoregulation.—Tap water usually is ade-
quate, but bottled water might be used where the
tap water quality is in question. Aging the water or
dechlorination is not necessary. Pseudomonas spp.
bacteria grow rapidly in water bowls, so bowls
should be changed and disinfected or washed in
hot soapy water every day.

Humidity is an important but often over-
looked factor. In general, iguanas require more
humidity than is typically present in our homes.
From a practical standpoint, maintaining humidity
levels of 50% is almost impossible, and such levels

result in blooms of mildew. Good ventilation is
essential to prevent the rapid growth of bacteria
and mold in the cage when humidity is added.
Humidity may be increased by using water bowls
with large surface areas to increase evaporation,
frequent spraying of the cage, or the use of humid-
ifiers. Different humidifier models produce hot or
cold mist. The former must be kept far enough
from the lizard to prevent burns. Machines kept
within the enclosure must be secured to prevent
iguanas from tipping them over.

Ultraviolet Requirements.—Ultraviolet
wavelengths (UV) are important for vitamin D
synthesis and calcium metabolism in diurnal lizards
that do not eat vertebrate prey. UV-A (nearwave,
320–400 nm) produces beneficial behavioral and
psychologic effects, but does not activate vitamin
D precursors in the skin. UV-B (middlewave,
290–320 nm) is necessary for vitamin D activa-
tion. Reptiles benefit from both UV-A and UV-B
light. Nevertheless, scientific studies into the spe-
cific requirement for UV light in captive lizards are
lacking, and specific requirements for UV wave-
length, intensity, and length of exposure are largely
unknown. Iguanas are known to bask for many
hours every day in the potent tropical sun, receiv-
ing levels of UV radiation that are difficult to
duplicate in captivity.

The sun is a more effective UV source than any
bulb, but certain precautions must be taken before
exposing captive lizards to direct sunlight. First,
window glass filters out UV rays, thus sunlight
through a window is of no benefit. A reptile in a
glass cage should never be placed in direct sunlight
or overheating and death may occur. Reptiles
should be in a screen or mesh cage to allow sun-
light to enter but, at the same time, prevent the
escape of the lizard. Part of this enclosure must be
shaded with an overhang or plants to allow the ani-
mal to get out of the sun. Iguanas basking in the
sun should be kept in an enclosure and not hand-
held, even with a leash, because direct sunlight can
result in temporary changes in personality, and nor-
mally tame lizards can become agitated and very
aggressive. These changes reverse readily when the
lizard is brought back inside. Lizards basking in
sunlight should be monitored to prevent overheat-
ing, exposure to predators, or theft, or any other
problem that might arise. Basking outside should
not be allowed if the ambient temperature is exces-
sively high. Even 15–30 min of direct sunlight a
week can be quite beneficial.

136 IGUANA Volume 10, Number 4



A number of artificial UV-B light sources for
reptiles are commercially available. Obviously a
bulb producing 5.0% of its emitted light as UV-B
is more efficient than one producing 2.0% UV-B.
Moreover, a 48-inch tube produces more light
than an 18-inch tube, and two tubes produce
twice as much light as a single tube. Traditionally,
fluorescent tubes have been considered better UV-
B sources than incandescent bulbs, but new prod-
ucts are available that claim to provide UV-B and
heat in a single incandescent bulb. New UV light
sources are becoming available on a regular basis,
and each should be evaluated based on the wave-
lengths of UV produced.

Caution should be taken to avoid human expo-
sure or eye contact with the UV rays, as these have
been associated with skin cancer and cataract for-
mation. Artificial UV light sources should mimic
natural photoperiods and be turned off at night.

Artificial light sources cannot replace natural
sunlight, and those reptiles with access to the sun
in outdoor enclosures, even on a screen porch or
patio, invariably have better growth, health, behav-
ior, reproduction, and longevity than those kept
indoors.

Visual Security.—Visual security is beneficial,
especially for nervous specimens. A shelter or retreat
should be provided for all cage inhabitants. Hiding
places can be made from a cardboard box, terra
cotta pottery, plastic flower pots, cardboard tubes,
sheets of cork bark, or driftwood. Arboreal iguanas

also should be provided with real or artificial plants
in which to hide. Some iguanas eat poorly and
become stressed if they lack visual security.

Disinfection.—Cages and food and water
bowls must be cleaned frequently. Three-percent
sodium hypochlorite solution is an effective and
economical disinfectant. The cage and its furniture
must be rinsed thoroughly before returning a lizard
to the cage. Keepers must wash their hands thor-
oughly after cleaning each cage and not transfer
water bowls, uneaten food, or climbing branches
between cages without disinfecting them first.

Quarantine.—Reptiles new to a collection
must be kept in a separate area from the main col-
lection for a minimum of 3 months. New arrivals
should have physical examinations, body weights
recorded, fecal examinations, parasite treatment,
and be monitored for appetite, normal behavior,
and symptoms of illness. At the very least, the
owner should inspect new arrivals. The main col-
lection should be fed and cleaned first and the
quarantined animals second, with no transfer of
animals, cages, food and water bowls, uneaten
food items, or cage furniture between the two.
Keepers must wash their hands and consider cloth-
ing changes after working with either collection to
prevent the inadvertent transfer of pathogens.
Ideally, different keepers would care for the two
collections. The farther apart the two collections
are physically, the less likely an epizootic will occur.
No transfer of air should occur between the two

137IGUANADecember 2003

Two Rhinoceros Iguanas (Cyclura cornuta) in a large outdoor enclosure. The lizard on the right is threatening the other one
with vigorous head bobs. Note the erect posture and orientation directly towards the other lizard. The other iguana soon
submitted by retreating to the far corner of the cage.



groups. When multiple animals are being quaran-
tined, they should enter and leave the quarantine
area as a group.

Communal Housing and Handling.—Pet
stores often display iguanas for sale in crowded
community tanks, suggesting that these are social
animals. In the wild they may form loose aggrega-
tions if food is abundant, but they also have the
opportunity to run away if they are being stressed
or threatened by other iguanas. Lizards locked in
a cage or room cannot run away. Male lizards are
more territorial than females, and react more vio-
lently to other males than to females. Hormone
fluctuations, and thus territoriality, are seasonal
and are manifested most acutely during the breed-
ing season. Iguanas gain little benefit from being
housed together, but cannot stress or injure each
other if housed separately.

When two or more lizards are kept together,
the more aggressive individual may physically
attack the subordinate one, sometimes inflicting

serious wounds. More often it dominates in more
subtle ways by keeping the subordinate lizard away
from food and heat sources. This allows the dom-
inant one to digest its food more efficiently, grow
faster, and have a more effective immune system
than the subordinate lizard. The subordinate in a
pair invariably suffers chronic stress, and thus fails
to thrive. Symptoms include slow growth, emaci-
ation, poor muscle tone, poor color, lethargy, and
susceptibility to infections and parasites. The solu-
tion is to separate the lizards. Reflective surfaces
and mirrors should be avoided, as lizards, espe-
cially males, will attack their own reflection.
Keepers might occasionally observe two lizards in
a cage to lie in the same spot and overinterpret
that they have a relationship. However, stress may
still be present.

Two or more iguanas may be kept together
only if certain requirements are met. First, the
enclosure must be large enough, with 1.5–2 times
the recommended area for the biggest iguana pro-

138 IGUANA Volume 10, Number 4

Multiple bite wounds on the back of a subordinate male iguana, which also suffered a fractured ulna as the result of an
additional bite. Seventy-eight stitches were needed to close the wounds. The owner had purchased two iguanas thinking
they were social and in need of companionship. As the lizards grew, they both turned out to be males and began to fight.
The owner tried to separate them by confining them in separate (and inadequate) 55-gallon aquaria in the same room. He
came home one day to find the larger male had broken out of his cage and into the cage of the smaller lizard, pinning him
down and chewing on him until the owner separated them.



vided for each iguana in the cage. Second, separate
feeding, basking, and hiding areas must be pro-
vided for each iguana. Spatial complexity, so the
iguanas can stay out of sight of each other behind
logs, driftwood, and plants, is crucial. Third, keep-
ers must be observant of the iguanas’ behavior. A
cage may appear suitable by the book, yet the indi-
vidual iguanas may require more space or addi-
tional shelters or basking sites. Different iguanas
have different personalities and requirements.
Finally, the keeper must be aware that two iguanas
simply may be incompatible. Just because they are
the same species does not mean that they will get
along. Females may dominate males, and smaller
lizards may dominate larger ones, so the largest
male is not always at the top of the social hierarchy.
Lizards that are initially compatible may begin to
fight months or years later. Keepers getting more
than one iguana should be prepared to provide
separate enclosures if the lizards become incom-
patible. Separate enclosures are not always enough,
and often cages must be kept in separate rooms.

Food and Feeding.—Wild Green Iguanas are
specialized folivores, eating primarily leaves from
trees. Captive iguanas are exposed to, and accept, a
number of food items they would never see in the
wild. The owner must patiently work with his or
her pet iguana and train it to eat a balanced diet.
The lizard should never be allowed to choose what
it eats, as taste and palatability do not necessarily
equate to nutritional value.

Suboptimal temperatures and other husbandry
conditions prevent adequate food intake and
digestion. Under poor captive conditions the best
diet in the world will be inadequate.

No captive iguana diet can be accurately
described as “proper.” The exact nutritional
requirements for Green Iguanas have never been
scientifically determined, and precise nutritional
requirements for this species are not known. Wild
iguanas eat leaves from trees that are not available
in captivity. We can approximate a nutritious diet,
but most formulations are based on anecdote,
experience, and speculation rather than scientific
feeding trials.

In captivity, herbivorous lizard diets should be
based on a variety of chopped, dark green, leafy
vegetables. Greens that contain oxalates, like
spinach, or goitrogens, like kale, should be used
sparingly. Fruit should be minimized, not because
it is toxic but because it dilutes the beneficial nutri-
ents of the other ingredients. In one study, adding

one cup of strawberries to one cup of romaine
reduced the protein and calcium concentrations by
two-thirds compared to romaine alone. A recom-
mended diet including ingredients, amounts,
schedules, and vitamin and mineral supplementa-
tion is described in the accompanying Table.

All plant material must be washed, chopped (a
food processor is recommended), and thoroughly
mixed. This will ensure a balanced diet in that all
food items will be eaten, rather than just the
favorites or the most tasty items. Prepare enough
for 4–7 days, store it in the refrigerator between
feedings, and serve it at room temperature or
slightly warmer. Offer food after the iguana has
had several hours to bask under its heat source in
the morning, leave it in all day and remove
uneaten food in the evening.

Grains such as bread, crackers, pasta, and seeds
are recommended in some iguana diet recipes.
This food group is low in the nutrients that
iguanas need, especially fiber, protein, and calcium.
Grains should be limited to occasional treats if
used at all.

Traditionally, animal protein sources have been
recommended. However, these lizards are vege-
tarians from birth, even though they might occa-
sionally accept unnatural foods (e.g., crickets or
even mice) in captivity. Although animal protein
sources often are recommended for iguanas, their
necessity has not been scientifically documented.
Any protein supplements should be plant-based.

Commercial iguana diets are available, but
vary in quality and palatability. The advantage of
these products is that they are easier to use than
preparing a balanced salad several times a week.
The disadvantage is that, in spite of claims that the
commercial diets are complete and balanced, they
may not be. Commercial diets that have high lev-
els of animal protein, fat, corn, soy, wheat, grains,
goitrogenic vegetables, fruits, or flowers should be
avoided. The main ingredient, which is always
mentioned first on the ingredient list, should be
alfalfa. Nutrient levels on a dry matter (DM) basis
should include plant-based protein > 20%, fiber >
15%, and calcium 1.4%. Pelleted or powdered diets
contain only 10% water compared to 85–90% in
salads. Consequently, these diets must be moist-
ened with water prior to feeding. Frozen diets can
be deficient in thiamine. Commercial iguana diets
may have a role in iguana nutrition but should be
limited to less than half of the total diet until more
is known.

139IGUANADecember 2003



140 IGUANA Volume 10, Number 4

Hatchlings 
(to 14” in length)

• Feed twice a day or provide continuous availability
• Plant matter finely chopped or shredded
• 1 small pinch of vitamin/mineral supplements per

feeding. Give vitamins 4–5 days a week and cal-
cium 7 days a week.

Juveniles 
(to 2.5 years of age or to 3 ft in length)

• Feed once a day
• Plant matter fine to medium chopped or shredded
• 1 small pinch of vitamine/mineral supplements per

feeding. Give vitamins 4–5 days a week and cal-
cium 7 days a week.

Adults 
(over 2.5 years of age or over 3 ft in length)

• Feed daily or every other day (an iguana cannot be
overfed when using the high fiber, vegetarian diet
recommended here)

• Plant matter coarsely chopped
• One full pinch of vitamine/mineral supplements per

2 lbs of body weight. Give vitamins 2–3 times per
week and calcium 4–5 times per week (unless
gravid or sick, then 5–6 times a week).

Ingredients
1. Calcium-rich leafy greens, 40–45% of the diet or

more with three or more items per feeding: turnip
greens, mustard greens, collards, pesticide-free
dandelion greens and flowers, clover, escarole,
carrot tops, parsley, nasturtium leaves and flowers,
and hibiscus leaves and flowers. Also offer endive,
romaine, mint, and cilantro.

Spinach, chard and beet greens have high levels
of oxalates which can tie up calcium, and kale,
bok choy, and broccoli leaves have high levels of
goitrogens. Both groups can be used, but in mod-
eration.

Iceberg, Boston, butter, and head lettuces have lit-
tle nutritional value compared to dark leafy
greens. Romaine is intermediate in value, and
should be used only in combination with the dark
leafy green mentioned above.

2. Other vegetables, 40–45% of the diet with a vari-
ety weekly: raw green beans, snow and snap
peas, squash, sweet potato, okra, bell pepper,
mushrooms, and yams. Thawed, frozen mixed

vegetables can be used occasionally. Grated car-
rot should be used only occasionally, as it also con-
tains high levels of oxalates. Vegetables with
lower nutritional values include cucumbers, toma-
toes, onions, olives, zucchini, and radishes.

3. Alfalfa is a good source of fiber and protein.
Alfalfa is available as minibales or pellets for small
mammals from pet and feed stores. Read pellet
ingredient labels to make sure alfalfa is the first
ingredient listed. Do not use mixes that contain
seeds and other ingredients. Alfalfa also is avail-
able as powder, tablets, or capsules from health
food stores. Pellets and powder should be soft-
ened by soaking them in water prior to feeding.
Be sure to use mature leaves and stems rather
than sprouts. If an iguana refuses to eat alfalfa as
offered, powder or crushed tablets can be added
at low levels to the salad, gradually increasing the
amount over several weeks.

4. Fruits should be used only as occasional treats or
supplements. Fruits are low in most nutrients
including protein and calcium, and have high lev-
els of phosphorus. Fruits dilute the good nutrients
found in leafy greens and vegetables. The follow-
ing may be offered: figs, papaya, melon, apple,
peaches, plums, strawberries, banana (with skin),
grapes, and kiwi.

5. Vitamin and mineral supplementation is advised.
Vitamin and mineral deficiencies are common in
iguanas. However, calcium and fat-soluble vita-
mins (A, D, E, and K) can be oversupplemented as
well as undersupplemented. To avoid oversupple-
mentation, natural sources from a varied diet are
the best choice, with moderate vitamin/mineral
use to balance the diet. To date, no documented
studies address specific requirements for any lizard
species.

Many commercial supplements are available for
reptiles, but none of these products is required to
prove potency or safety. Products vary widely in
levels of ingredients. Look for a ratio of roughly
100 parts Vitamin A to 10 parts Vitamin D3 to 1
part Vitamin E. Human products with Vitamin D3
(rather than D2) may also be used. For minerals,
use powdered calcium carbonate (cuttlebone
shavings is one source) or calcium gluconate.

Vitamin powder on top of the salad may make it
unpalatable. The powder should be mixed in thor-
oughly. If you can see the powder, you probably
used too much.

Recommended Diet 
for Captive Green Iguanas



Green Iguanas, especially hatchlings, in retail
outlets are often anorexic, underweight, and weak.
They may weigh less than 10 g and have a sunken
abdomen and a bony pelvic girdle. These lizards
should be force-fed an appropriate vegetarian diet
such as a commercial tube feed mixture for rabbits
or a gruel of rabbit pellets, as opposed to a liquid
diet for carnivorous dogs and cats, at 1–3% of their
body weight every two days. At the same time, the
juvenile lizards should be offered a finely chopped
diet, as described in the accompanying Table, until
they are eating on their own.

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141IGUANADecember 2003

An emaciated Green Iguana acquired by the Mid-Michigan
Reptile Rescue. Photograph by Stephanie Beiser.

A healthy Exuma Islands Iguana (Cyclura cychlura figginsi)
enjoys a properly prepared meal. Photograph by Juliann Sweet.




