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IGUANA  •  VOLUME 12, NUMBER 3  •  SEPTEMBER 2005 177MONITORS

The family of monitors is monotypic, and all living mem-
bers belong to the genus Varanus. The genus is subdivided

into nine subgenera. Two distinct geographical radiations have
been identified (Böhme 1988a, 1993). The Afro-Asian radia-
tion includes the subgenera Psammosaurus, Empagusia,
Philippinosaurus, and Polydaedalus. The Indo-Australian radia-
tion includes the subgenera Odatria, Varanus, Papusaurus,
Euprepiosaurus, and Soterosaurus.

Monitors are restricted in distribution to the Old World,
where they inhabit the tropical and subtropical climatic zones of
Africa, Asia Minor, South and Southeast Asia, Australia, and the
Indo-Australian archipelago. Australia appears to be a significant
hub for monitors worldwide, with 25 species and ten subspecies
in three subgenera.

Monitors occupy almost all habitats: they live in sandy
deserts, open savannas, and even tropical rain forests. Rivers and
lakes are used as habitat refugia by some species. Monitors can
be categorized by their preferred habitat. These include: water
monitors, ground-, rock-, and tree-dwellers.

All monitors share certain characters. They all have a com-
pletely ossified skull, which makes it possible for them to swal-
low large food items without the risk of pressure on the brain.
The throat can be enlarged by raising the hyoid cartilage appa-

H U S B A N D R Y

Captive Care of Monitors1

Part I: Introduction and Housing
Bernd Eidenmüller

Frankfurt, Germany 

1 Adapted by AJ Gutman from B. Eidenmuller, Monitors: Natural
History — Captive Care — Breeding. Herpeton Verlag, Offenbach,
Germany. 

Juvenile Varanus kingorum. This small species needs a rocky habitat equipped with many hiding places. 



ratus, helping them to swallow food. This inflation of the gular
region increases the overall body size, and also acts to help intim-
idate enemies or impress rivals. All monitors have four limbs
with five toes that are equipped with strong, backward-curving
claws. The head is situated on a long neck, the eyes have round
pupils, a distinct tympanum is clearly developed, and the tongue
is very long and deeply forked. Using the tongue, monitors
extract minute particles from the air or substrate and convert
these into a traceable scent using chemoreceptors in Jacobson’s
organ, which consists of a pair of pits in the roof of the mouth
into which the tips of the forked tongue are inserted. These cues
can be used to detect food, rivals, or sexual partners.

The difference in size between the largest (Komodo
Dragon, V. komodoensis, from the island of Komodo, length to
350 cm, weight 150 kg) and smallest (the Short-tailed Monitor,
V. brevicauda, from Australia, length about 23 cm, weight about
20 g) living monitors spans almost four orders of magnitude
(i.e., V. komodoensis is 7500 times heavier than V. brevicauda).
This represents the largest size disparity between vertebrates
within a single genus in the world.

Care
As some species of monitors can reach both substantial total
length and body mass, potential keepers must carefully consider
the amount of space needed to properly maintain these animals.
Most enthusiasts are limited in the size of enclosures they are able
to provide. Given such constraints, the monitors in the subgenera
Odatria and Euprepiosaurus are the most appropriate, although
nearly all species within these subgenera are from either Australia
or the Indonesian islands. The export of monitors from Australia
is strictly forbidden, and export from Indonesia is very restricted.
Therefore, captive-bred animals must be sought. These animals
are legal and offered regularly in fairly large numbers.

Which Species Suits Me?
Deciding which species to purchase should be guided by the
amount of space you have available for an enclosure and the
amount of money you are prepared to pay. If you purchase a rel-
atively inexpensive monitor such as the Water Monitor (V. sal-
vator) from a pet shop, you need to be aware that this animal, if
properly fed, has the potential to grow to more than two meters
in less than two years. It will very quickly outgrow that small
enclosure in the living room. Furnishing the enclosure should
be another consideration. Preferably, the enclosure should be set

up to mimic the type of habitat and climate that your particu-
lar species of monitor would encounter in the wild.

In most monitor species, the sexes are almost impossible to
differentiate. Although a degree of sexual dimorphism (variable
size and color) exists in some species, this tends to be the excep-
tion rather than the rule. Many lizards and snakes are easily
sexed by inserting a rounded probe into the hemipenial pockets
at the base of the tail. The probe slides posteriorly into the pouch
in the direction of the tail tip. The length of the inserted probe
is used to determine sex, with males having a deeper probe depth
than females. This method is not appropriate for sexing moni-
tors, as females have a similar pouch at the base of the tail, which
is the mirror of the hemipenial pocket of the male. This
hemipenial structure in the female has been described as the
hemiclitoris (Böhme 1995, Ziegler and Böhme 1996a).
Similarly, the clusters of spines located at the base of the tail in
some monitor species do not always indicate sex. In V. tristis, this
feature is prominent in males but not females. In order to be
100% certain of sex in monitors, a reptile veterinarian must per-
form an endoscopic inspection of individual animals (Schildger
and Wicker 1992, Schildger et al. 1993).

Captive-bred animals obtained from a private breeder are
generally healthy and should present few maintenance problems.
Wild-caught animals from reptile dealers are very often of infe-
rior quality; these animals are likely to be highly stressed from
capture and transport. Although the initial cost may be a little
higher, captive-bred animals are likely to be much more cost-
effective in the long term. The exception is for species new to
the market, which may not as yet have been bred in sufficient
numbers for their breeding biology to have become understood
by specialist keepers who will eventually make them available as
captive-bred progeny.

Opportunistic infections often appear in parallel with par-
asitic infestations, thus wild-caught animals should be observed
for at least six weeks in a quarantine enclosure following acqui-
sition, without exception. During this period, feces should be
collected and examined by a reptile veterinarian for parasites.
Medication should not be administered without direct instruc-
tions from a reptile veterinarian. Visible external injuries should
also be referred to a veterinarian. Problems seldom appear with
captive-bred animals, although some exceptions to this may

178 IGUANA  •  VOLUME 12, NUMBER 3  •  SEPTEMBER 2005 EIDENMÜLLER

Juvenile Varanus glauerti basking in a terrarium.

Juvenile Varanus storri are often aggressive towards cagemates and must
be raised separately.



IGUANA  •  VOLUME 12, NUMBER 3  •  SEPTEMBER 2005 179MONITORS

become apparent as more and more people keep monitors as
pets. Varanus storri, for example, should be housed individually
and paired only for the breeding season, as they tend to fight.

The wide geographic distribution of some monitors presents
another problem. A visual inspection of a wild-caught animal will
not necessarily reveal its point of origin. With considerable cli-
matic divergence within the distribution ranges of some monitors,
problems may occur in synchronizing mating with seasonal dif-
ferences between locations. A V. tristis from Kingoonya in South
Australia may mate at one time of the year and the same species
from Daly Waters, some 2000 km north in the tropics, may mate
at another time of year. Thus, even when two animals of the same
species are paired, breeding success can remain elusive. With cap-
tive-bred animals, this does not appear to be a big problem, nor
with animals that are long-term captives (i.e., three years or more).

To date, little attention has been paid to the territoriality of
monitors. In captivity, one animal simply cannot be replaced
with another. Monitors have an acute sense of smell and any
new intruder in the cage is immediately recognized, a phenom-
enon I have observed in V. storri. When a new animal is intro-
duced into a cage, it immediately begins to tongue-flick to inves-
tigate the entire enclosure. In several places within the cage, it
will rub its cloaca, presumably to mark its territory, as well as to
inform rivals and sexual partners living in the area/enclosure of
its presence (Eidenmüller 1993).

The Enclosure
The goal of every responsible private keeper should be to strive
for species-specific care for his or her captive monitors. Each
species will have different needs in terms of climate (including
temperature, lighting and humidity), housing, and diet.

The captive habitat should be set up to simulate as closely
as possible the natural environment of its inhabitant(s).
Obviously, attempting to recreate natural elements such as flood
and fire is neither simple nor desirable. However, this still leaves
us with any number of parameters to manipulate in order to
provide the greatest natural comfort and the highest probability
of breeding success for our captive charges.

Monitors appear unable to distinguish between types of
branches in the enclosure, be they cherry tree or some other tree
branch. In my experience, the most important consideration is
allowing the animal to feel secure when climbing and holding a
branch. Illumination is perhaps the most important and one of
the most overlooked elements of the captive setup. Since artifi-
cial lights cannot approach the degree of illumination provided
by natural sunlight, in general, the highest degree of illumina-
tion that can be provided without overheating the enclosure is
most appropriate. Diet also is of great importance and appro-
priate food items (mice, rats, chickens, insects) to approximate
each species’ natural diet should be provided.

Social conditions within any one enclosure must be closely
monitored. Housing animals of unequal size together may result
in one becoming prey for another. Parasitic infections in captive
animals also require immediate intervention. Under natural con-
ditions all monitors carry both endo- and ectoparasites and
appear unaffected except in exceptional circumstances. In cap-
tivity, any number of factors can result in a parasitic imbalance,
which can rapidly overwhelm an already stressed animal.

Let me again emphasize that the care of animals should
approximate conditions in the wild as closely as practicable. The
highest objective in captivity should be to maintain fit and
healthy captives, capable of reproduction. Enclosure size and fur-
nishings need to be adapted to the natural movement and
behavior patterns of the animals you wish to keep.

Different species will have different spatial needs within an
enclosure. Every keeper should offer the animals as much space
as possible. Recommended enclosure size for tree dwelling ani-
mals is 5 x 2 x 4 (length x width x height) times greater than
snout-vent length (SVL) or 4 x 2 x 5 times SVL. For ground
dwelling animals, cages should be 5 x 2 x 2 times SVL. These
guidelines will ensure that your monitor has sufficient room to
move. For quarantine and hibernation enclosures, these meas-

A tree dweller, such as this Varanus timorensis, benefits from plenty of
vertical structure within a terrarium.

An albino juvenile Varanus kingorum relaxes on a bare branch.



180 IGUANA  •  VOLUME 12, NUMBER 3  •  SEPTEMBER 2005 EIDENMÜLLER

urements can be reduced by half. During quarantine, the enclo-
sure should be cleaned frequently and a small space can be
cleaned with relative ease. During hibernation at lower temper-
atures, the movements of the animals are restricted and a smaller
enclosure is sufficient.

Water monitors have different cage requirements compared
to terrestrial and rock-dwelling monitors. They require a fairly
large water tank in which they can swim and dive. A small water
dish is not sufficient. Animals from arid regions should be pro-
vided with dust-free sand as ground cover. Sand need not be
sterilized before use. Cypress mulch is the perfect substrate for
animals from the tropics. This substrate retains moisture over
long periods, thus increasing humidity within the enclosure.
Mulch should not be sterilized, as this will kill off natural
microorganisms that serve to retard the growth of fungi.

Furnishings should be such that they are compatible with
the general movements of the monitor being housed. Most
monitors are good climbers, and both the side and rear walls of
the enclosure should be formed so that they can be used for
climbing. This will increase the amount of activity area available
to the animals. Ground- and rock-dwelling animals from desert
areas will make ready use of a terrarium that has a rear wall mod-
eled with styrofoam and epoxy-resin. As the resin dries, the
whole wall can be dusted with sand to give it a stone-like texture
(Eidenmüller 1989, 1992a). For tree monitors, thick cork sheets
can be affixed to the side and rear walls (Eidenmüller and
Wicker 1992) to form climbing areas. Cage structure can be
enhanced further by using tree branches in the enclosure.
Smooth branches should be avoided, as they are difficult for the

animals to grip. The overall layout of the terrarium is basically
one of personal preference. My own water monitor terraria are
built on top of an aquarium. Atop the aquarium, I used
Styrofoam and epoxy resin to construct a ground area onto
which the animals climb from the water. This type of layout
offers the monitors both water for swimming, and a large over-
hanging ground area. The styrofoam rock area also serves as a
basking area suitable for thermoregulation (Eidenmüller 1990,
1995, Eidenmüller and Wicker 1995).

Since live plants rarely survive in monitor enclosures, I do
not recommend their use. Ground-dwelling monitors will
inevitably dig, and during these excavations plants become
uprooted and die. Even the hardiest plants can only survive this
activity for a short period. Living plants in an enclosure for rain-
forest inhabitants (e.g., V. prasinus) appear very natural; however,
even trees like the robust Fig Tree (Ficus benjamina) die in a very
short time when continually subjected to monitor claws. Plastic
plants do very well in some of my enclosures. They appear fairly
natural and are easy to clean. Animals do not seem to care
whether the cover is natural or not. When using artificial plants,
however, be careful that monitors do not ingest any broken parts
of these plants along with their food.

Proper lighting is critical for the well-being of monitors in
captivity; nevertheless, I find that many keepers fail to provide
sufficient illumination in their enclosures. No amount of artifi-
cial light will replace natural lighting conditions. Whereas low-
intensity bulbs and common fluorescent tubes may be more effi-
cient in terms of initial cost and long-term energy expenditure,
and may even provide lighting that appears sufficient to the
human eye, they represent a false economy and will inevitably
result in health problems for captive monitors in very short
order. In my experience, the use of mercury vapor lamps has a
positive influence on the behavior of animals. Mercury vapor
lamps radiate ultraviolet (UV) light, which is critically impor-
tant in a monitor enclosure. Ultraviolet lighting must be
installed in such a manner that animals have direct access to it
without any intervening glass barriers that can block the UV
rays. The temperature range produced within the enclosure
should be carefully measured to avoid the problem of overheat-
ing. To this end, proper ventilation of the enclosure is essential.

Although animals such as this Black-throated Monitor (Varanus albigu-
laris ssp.) can become quite tame, potential owners must consider the
amount of space required by a pet that can attain a length of up to 200
cm.

JO
H

N
 B

IN
N

S

Varanus mertensi is a highly aquatic species from Northern Australia
and even a juvenile requires a fairly large swimming area. Appropriate
housing can be constructed above an aquarium.



Also, ensure that no animal can come in direct physical contact
with any of the heating lamps. Burns from lights are all too com-
mon, and can potentially result in fatalities.

All monitors are diurnal, and should be provided with a day-
time photoperiod of appropriate length and intensity. The ani-
mals must also be able to regulate their body temperatures. A
basking area under a spotlight should be provided as well as
cooler areas more distant from a direct heat source. Many keep-
ers think that desert animals require high to very high tempera-
tures. In actuality, animals in the wild can move from areas with
high solar radiation to areas that offer protection from extreme
temperatures. This movement in and out of high temperatures is
known as “shuttling” behavior and is common to many reptiles.

Conditions that support this type of behavior are difficult
to reproduce within an enclosure. Keepers rarely have a terrar-
ium deep enough to offer their captive monitors the opportu-
nity to dig into 50 cm of sand or other substrate. I would rec-
ommend keepers use a heating source that has been installed to
heat only one half of the enclosure. In many of my own enclo-
sures, I have a 60-watt spotlight with a wide angle of light
directed onto a flat rock some 40 cm away. This provides a good
thermal gradient within the cage, but allows the monitor to
attain an optimum body temperature without risk of overheat-
ing. I would not recommend the use of a ceramic heater, because
it does not give off light; the animals do not realize that the
amount of heat generated is substantial and can cause severe
burns or even death. Larger monitors will sometimes incur local-
ized burns under a spotlight because the part of the body directly
under the lamp heats up to burning point while the tempera-
ture over the rest of the body is insufficient to warn it of the dan-
ger presented by the spotlight.

In Sri Lanka, Water Monitors (V. salvator) occasionally suf-
fer dorsal burns due to their propensity for hiding in rubbish
heaps. When the rubbish is burned, the animals are caught with
a low body temperature while the flames create a high single-
point temperature.

An under-tank heating pad can be installed beneath the
preferred hot spot. If a heating cable is used, it can be coiled
around one half of the enclosure to create a temperature gradi-
ent. Because most monitors are accomplished at digging, the
cable must be secured so that the animals cannot dig it out or
sustain electric shocks. The best method is to install the cable
under the half of the terrarium that is to be heated.

References
Böhme, W. 1988. Zur Genitalmorphologie der Sauria: Funktionelle und

stammesgeschichtliche Aspekte. Bonn zool. Monogr. 27:1–176.

Böhme, W. 1993. Systematik und Stammesgeschichte der Warane – Übersicht
zum heutigen Stand. Monitor 2(1):7–12.

Böhme, W. 1995. Hemiclitoris discovered: A fully differentiated erectile structure
in female monitor lizards (Varanus spp.). J. Zoo Syst. Evol. Res. 33:129–132.

Eidenmüller, B. 1989. Beobachtungen bei der Haltung und Nachzucht von
Varanus (Odatria) tristis orientalis Fry, 1913. Salamandra 25:265–271.

Eidenmüller, B. 1990. Beobachtungen bei der Haltung und Nachzucht von
Varanus (Varanus) mertensi Glauert, 1951. Salamandra 26:132–139.

Eidenmüller, B. 1992. Bemerkungen zur Haltung von Waranen. Monitor
1(1):7–13. 

Eidenmüller, B. 1993. Bisher nicht beschriebene Haltungsweisen von Varanus
(Varanus) flavirufus (Mertens, 1958), Varanus (Odatria) acanthurus
Boulenger 1885, and Varanus (Odatria) storri Mertens 1966 im
Terrarium. Monitor 2(2):12–21.

Eidenmüller, B. 1995. The successful breeding of Mertens’ Monitor Lizard,
Varanus mertensi. Vivarium 7(2):18–20.

Eidenmüller, B. and R. Wicker 1992. Varanus (Odatria) prasinus beccarii
(Doria, 1874), Pflege und Zucht. Salamandra 28:171–178.

Eidenmüller, B. and R. Wicker. 1995. The successful breeding of Mertens’
Monitor Lizard Varanus mertensi, Glauert, 1951. Herpetofauna 25(2):4–7.

Schildger, B, M. Kramer, H. Spörle, M. Gerwing, and R. Wicker. 1993.
Vergleichende bildgebende Ovardiagnostik bei Echsem am Beispiel des
Chuckwallas (Sauromalus obesus) und des Arguswarans (Varanus
panoptes). Salamandra 29:240–247.

Schildger, B.-J. and R. Wicker. 1992. Endoskopie bei Reptilien and Amphibien
– Indikationen, Methoden, Befunde. Der praktische Tierarzt 6:516–526.

Ziegler, T. and W. Böhme. 1996. Zur Hemiklitoris der squamaten Reptilien:
Auswirkungen auf einige Methoden der Geschlechtsuntersuchungen.
Herpetofauna 18(101):11–19.

IGUANA  •  VOLUME 12, NUMBER 3  •  SEPTEMBER 2005 181MONITORS

Varanus pilbarensis is a small, attractive rock dwelling monitor from Western Australia.




