| HUSBANDRY OF THE GREEN IGUANA
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Jason Hutcheson, DVM
For Pet’s Sake: The Avian and Exotic Animal Hospital of Atlanta
The common green iguana (Iguana iguana) is a tree dwelling tropical lizard
found in Central and South America which has the potential to grow up to six
feet in length. Iguanas have various temperaments from being docile to nervous.
at times they can enjoy human affection. Iguanas are often represented as
undemanding pets that can be cared for easily and are “veterinarian free.”
Unfortunately, this is not true. The dietary and environmental needs of iguanas
are very difficult to reproduce in captivity. The amount of misinformation given
in the pet trade makes it doubly hard for them to survive. This article will
provide accurate information on the care of iguanas as well as some of the
common medical problems that occur.
DIET
In their native habitat, iguanas feed on nutrient rich leaves and flowers of
trees, plants, and vines. They do not hunt insects or small animals as is
sometimes reported. Iguanas have specialized bacteria in their hindgut that
break down or ferment the high fiber content of their diet (much like a horse).
This releases usable energy in the form of complex carbohydrates which compose
30-40% of the total energy that iguanas need to live. In the wild, iguanas bask
in the sun to seek an ideal body temperature above 90 degrees Fahrenheit which
is required for fermentation of their food.
Since we cannot duplicate the diet of wild iguanas for our captive pets, the
best we can do is provide foods which best meet the high calcium, vitamin, and
mineral requirements of iguanas. This is not too difficult. Dark leafy greens
such as carrot tops, kale, collard, turnip, and mustard greens are readily
available in grocery stores or farmer’s markets. Best of all, they are
inexpensive. We do not recommend any of the commercially available iguana diets
at this time. Many do not meet the dietary needs of iguanas despite their
claims.
Feed your iguana daily as much as it will consume in two to three hours.
These foods can spoil quickly and should not be left in the cage for long
periods. You may want to feed young iguanas twice a day.
• Protein
Young iguanas need a balanced protein source in order to grow. A high
quality maintenance dry dog food such as Science Diet Canine Maintenance is a
good choice. DO NOT substitute puppy, growth or feline formulas for the
maintenance dog food because these are too high in protein. To prepare the
kibble, soak the nuggets 20-30 minutes in warm water until completely soft. It
is important to mix the dog food with the greens thoroughly to prevent the
animal from eating only its favorite foods. A food processor works well for this
purpose.
Recent data may indicate that iguanas fed an excessive amount of protein may
be at risk of severe kidney problems later in life. For this reason, we are
recommending that only the baby and juvenile iguanas be fed dog food in the
manner described above. Iguanas grow in different stages like any other animal
and so their feeding requirements change as they grow. The proportions for each
stage in life will be addressed in the next section.
• Calcium
Calcium supplementation is an absolute necessity for pet iguanas. The diet
we have recommended is already rich in calcium but still falls short when
compared to the wild diet. Please refer to the table “Calcium Content of Common
Foods” at the end of this article. Most commercial supplements are made from
bone meal (calcium phosphate) and are intended for animals that already have an
adequate supply of calcium in their diet. Iguanas need a phosphorus free calcium
supplement as the phosphorus actually binds up the dietary calcium and prevents
its utilization by the iguanas body. We recommend Rep-Cal (not Reptical or
Reptivite) which as inexpensive and safe calcium carbonate supplement that also
contains vitamin D3, which is necessary for calcium absorption in the gut.
Additional vitamin supplements are not necessary as dog food is a heavily
supplemented product and provides a balanced source of vitamins for young
iguanas. Adding more vitamins to this diet could lead to an overdose of vitamin
A or D resulting in serious illness.
• Here are the proportions of food recommended for feeding at each life
stage:
Small infant iguanas (less than 1 pound or 1 foot in length) should be fed a
diet of 25% softened dry dog food and the other 75% should consist of the dark
leafy greens aforementioned. Dust this mixture lightly with Rep-Cal at each
feeding. Young iguanas grow quickly and should weigh close to one pound and be
one foot long at one year of age. It is better to offer a little more than you
think your iguana will need until you learn how much your iguana will eat. If it
cleans it plate at each meal, more should be offered at the next meal.
Medium adolescent iguanas (two to three pound and two to three feet in
length) should be fed 15% dog food and 85% greens. Calcium supplementation
should be continued daily.
Large adult iguanas (more than three pounds and three feet in length) should
primarily be fed dark leafy greens. Once or twice weekly add Rep-Cal to the
greens.
HOUSING AND ENVIRONMENT
• Space
Young iguanas may be housed in an aquarium, but will soon outgrow it. It is
not true that they will only grow to the size of their environment. Adult
iguanas need at least 6 cubic feet which means you will probably have to build a
cage. Some owners will give the iguana free run of an entire room, but iguanas
need high heat and humidity and this cannot be provided in such a large area.
• Heat
Iguanas in the wild live in the hot, humid jungles of Latin America. This
makes high temperatures and high humidity very important for their captive
environment. Iguanas are basking animals which means they warm themselves by
sitting under a bright overhead heat and light source. The basking area of the
cage should be 90-100 degrees F (necessary for proper fermentation of food). A
high wattage flood lamp in a reflective fixture will provide the needed heat.
Hot rocks should not be used for iguanas because they often cause serious burns.
DO NOT USE THEM! Daytime temperatures should be in the high 80’s and nighttime
temperatures no lower than 75 degrees F.
At night it is necessary to heat the entire air space surrounding the iguana.
Pearlco Ceramic heating elements provide radiant heat without subjecting the
iguana to constant light (a stress for people and animals). Despite reports in
some literature, iguanas are bothered by red light bulbs at night; these bulbs
are unsuitable as a heat source. A secondary source of heat should also be
provided. Under the tank heaters are a hi-tech, safe heating pad designed to run
continuously at a constant temperature. You need at least one reliable
thermometer in the cage to be sure you are providing adequate heat.
• UV Light
Iguanas have an absolute requirement for ultraviolet (UV) light which they
normally get from the sun. Even captive iguanas fed a proper diet will suffer
calcium deficiencies if ultraviolet light is lacking. Iguanas need UV light in
order to utilize the calcium in their diet. Therefore, iguanas must have access
to direct sunlight for as long as the seasons will allow. This means there can
be no glass or plastic between the iguana and the sun as these materials absorb
the ultraviolet rays. A screened-in porch or an outdoor enclosure made of strong
wire mesh is ideal. If nighttime temperatures are above 75 degrees F, iguanas
can be kept outside 24 hours a day. As temperatures fall, however, move them in
at night.
When the iguanas cannot be kept outdoors you must use an artificial source of
UV light. There are especially made fluorescent bulbs that provide some UV
light. Plant grow lights and fish aquarium bulbs are not suitable. As a rule of
thumb, if the light emits a yellow color, it is not producing light at the
ultraviolet end of the spectrum. Remember, even the best bulbs cannot substitute
for sunlight and should only be use when absolutely necessary. In addition,
these bulbs should be changed every six months because their UV output goes down
drastically after then.
• Water
Although iguanas get most of their water from their food, a large container
is still necessary for soaking and for helping maintain the high humidity of the
enclosure. Soaking helps the iguana defecate and shed its skin. Some iguanas are
reluctant to soak themselves; these individuals should be soaked every other day
in the bathtub. Turning on the shower mimics the rainstorms from their native
habitat.
HEALTH ISSUES
• Sex Determination
Iguanas cannot be sexed until approximately two years of age. At this time,
male iguanas will undergo an enlargement of the femoral pores located on the
undersides of the back legs. the pores of females will remain small and flat.
Males also tend to develop longer spines and a larger dewlap. Males may exhibit
behavior characteristics such as bobbing and shaking of the head. The hemipenes
can sometimes be seen as a swelling at the base of the tail.
• Fibrous Osteodystrophy
Young iguanas suffering from calcium deficiencies are presented to the
veterinarian for swollen legs, a swollen jaw, fractures of the legs and spine,
and/or not eating or walking well. Larger iguanas with calcium deficiencies will
exhibit muscle tremors and paralysis in severe cases.
When on a calcium deficient diet, the body pulls calcium out of the bones
just to survive. This weakens the bones. Then the body attempts to strengthen
the bones by laying down fibrous connective tissue which causes the bones to
appear swollen. This produces a syndrome called fibrous osteodystrophy. Although
the legs appear fat, this is actually disease. The jaw becomes soft and swollen.
The muscles of the tongue pull back the jaw which causes it to become shortened
and bow out at the sides. The lips no longer meet and the gums are constantly
exposed to air. The gums become dry and inflamed and crusts build up producing a
syndrome called “exposure gingivitis.” Pet stores mistakenly call the “mouth
rot” which is a bacterial infection of the mouths of snakes. Though there may
also be a bacterial infection, these symptoms are all signs of calcium
deficiency in iguanas.
• Egg Binding
Female iguanas will ovulate with or without the presence of a male (just
like chickens) in captivity but, lacking a proper nesting site, will not lay the
eggs. When this happens, the eggs have to be removed surgically. The surgery is
expensive and may endanger the life of an already sick animal. If you have
female iguanas we recommend having them spayed before egg binding occurs.
• Abscesses
Iguanas are often seen with abscesses around the face and on the feet. This
condition is caused by bacteria that get into the blood because of a weakened
immune system. Poor diet and environmental conditions cause overall poor health
and make iguanas susceptible to bacterial infections. Abscesses require lancing
and flushing by a veterinarian as well as treatment with antibiotics.
• Burns
Burns are a common husbandry problem in iguanas, especially those who have
hot rocks in their cages. Hot rocks are poorly made and often have spots that
are extremely hot. When given a choice between burning or being too cold,
iguanas will choose to burn. Any exposed lights or heating pads in their cage
can also cause burns.
• Parasites
Iguanas are susceptible to a variety of parasites. Some parasites like
pinworms normally inhabit the digestive tract without doing any harm to the
animal (they may actually aid in digestion of food). The presence of a low level
of parasites called flagellates is also considered normal in the iguana to
facilitate the fermentation of foodstuffs in the hindgut. However, stressful
conditions (poor diet, low heat, the pet trade) can lead to an overpopulation of
parasites such as giardia which can cause stunted growth and a pot-bellied
appearance. These parasites can also cause foul smelling diarrhea and
dehydration that causes the iguana’s skin to form sharp creases along its sides.
External mites, which are commonly seen in snakes, are not frequently seen in
iguanas. The parasites that can inhabit iguanas cannot be treated with
medications from your local pet store. Your veterinarian will provide the safest
and most effective treatment for any parasite problem.
• Constipation
Iguanas kept on cat litter or aquarium gravel often have blockages that
require medical intervention. Iguanas can become severely constipated from lack
of heat, poor diet, and from not being soaked frequently.
We hope that the information in the article will help you take the best care
of your pet iguana. Remember that any pet is a responsibility, and it is your
responsibility to care for it in the healthiest manner. Your veterinarian can
help you with many questions or problems that you may have or direct you to a
knowledgeable source.
Copyright 2005 For Pet’s Sake and Jason Hutcheson, DVM.
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