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Chuckwallas (Sauromalus spp.) are iguanid lizards inhabiting
the southwestern portion of North America. Approximately

seven species have been described and generally accepted, and
additional subspecies or full species can be added to the count,
depending on how one defines those terms. The common
Chuckwalla (Sauromalus ater Duméril 1856) is the most widely
distributed species, occurring from southwestern Utah and south-

ern Nevada, south through the eastern portion of southern
California and western Arizona, down into the Baja Peninsula
and the Sonoran Desert of México. Until recently, U.S. popula-
tions often were referred to as S. obesus (see article on p. 78). One
of the largest native lizards in the United States, Chuckwallas
range in size from 13 to over 20 cm in snout–vent length (SVL)
(Stebbins 1985). Adult males are larger than adult females. The
head is distinct from the body and the heads of males are much
broader than those of females. Scales at the back of the head form
small spikes, which are most prominent in adult males. These
lizards have stout bodies and, when relaxed, have multiple folds
of skin along their sides.

Coloration varies considerably over the range of S. ater.
Some animals have 3–5 dark dorsal bands on a light background.
Others have solid black heads and bodies with either white,
bright orange, or red tails. Numerous variations on these patterns
occur. Juveniles tend to have the dorsal bands with black freck-
ling in the interspaces. Most young animals also have bands on
the tail, and these may be retained into adulthood in some pop-
ulations. The transition to adult coloration generally occurs
within the first two years of life.

These lizards inhabit arid regions with moderate shrub cover
and usually are found on or near rocky outcrops with plenty of
crevices in which they take refuge from predators and at night.
Primarily diurnal, they actively forage for plant material and can
regularly be found climbing low foliage to retrieve leaves from
overhead branches. When threatened, they retreat into rocky
crevices and fill their lungs with air, expanding the torso and
compressing their body into the crack, preventing extraction by
potential predators and even most collectors (a pry-bar is stan-
dard collecting gear when hunting Chuckwallas). Although they
look somewhat cumbersome with their relatively short legs and
stout bodies, they are agile runners and can move with surpris-
ing speed when threatened.

Chuckwallas in Captivity
Because they are diurnally active and tend to have calm disposi-
tions, Chuckwallas can make excellent pets. They can be housed
in small groups, if enough cage space is provided. Their moder-
ate size (compared to most other iguanids) also means that an
enclosure does not need to fill an entire room to house a breed-
ing group. Taking into consideration their requirements in cap-
tivity, they are an easy and rewarding species with which to work.

114 IGUANA  •  VOLUME 11, NUMBER 2  •  JUNE 2004 AUCONE

H U S B A N D R Y

Adult male Sauromalus ater, Joshua Tree National Monument,
Porcupine Wash, California. Photograph by Brad Hollingsworth. 

Captive Husbandry of the Chuckwalla
(Sauromalus ater)

Brian Aucone

Curator of Reptiles, Amphibians, & Aquatics
Oklahoma City Zoo



IGUANA  •  VOLUME 11, NUMBER 2  •  JUNE 2004 115SAUROMALUS ATER

Enclosure
The type of enclosure one should select for Chuckwallas depends
on the number of animals to be housed and how natural and aes-
thetically pleasing the display is to be. At a minimum, for adult
animals, a 40-gallon breeder-size tank can suitably house an adult
pair. This setup provides approximately 4.5 ft2 of floor space. In
general, another 2–2.5 ft2 of floor space is necessary for each
additional animal in order to provide adequate individual space
for each lizard. Cages can be built out of wood or other materi-
als (as long as they are constructed in a fashion that permits thor-
ough cleaning), but floor space should be a primary considera-
tion. Vertical height is much less important. Also, any cage,
whether purchased or constructed, should have good ventilation.
Chuckwallas like hot basking spots and these must be provided.
If ventilation is inadequate, temperatures in the enclosure can
quickly rise to dangerous levels.

Props and substrate for the cage should be selected based on
functionality as well as aesthetics; more elaborate designs often
require considerably more maintenance. An effective substrate
can be made up of playground sand and dirt in approximately a
2:1 ratio. Gravel should not be used as it can be inadvertently
ingested and cause intestinal impaction. Wood shavings or other
substrates, such as ground coconut shells, are not recommended
because they retain moisture that can lead to bacterial or fungal
growth, which can adversely affect the health of the animals. The
substrate should be at least 2–3 in deep to allow for digging.
Individual fecal pellets should be removed frequently, and the
entire substrate should be replaced at least twice each year to
ensure adequate cleanliness.

Props in the cage should consist minimally of piled rocks,
leaving crevices and openings into which the animals can retreat
for security. This mimics their natural habitat and is much more
suited behaviorally than a hide-box. When piling rocks, be sure
that they are stable; if they shift they could injure or kill the
lizards. Artificial rock outcroppings may be constructed (see arti-

cle in IGUANA 11:39–51). These often are more stable and eas-
ier to clean than piles of real rocks, and are readily accepted by
Chuckwallas. Regardless of whether natural or artificial rocks are
used, if multiple specimens are being housed, retreats should be
sufficiently abundant so that each lizard has access to a separate
area. In addition to rocks, props such as branches or plants can
be added to the enclosure. When using live plants, however, keep
in mind that Chuckwallas are herbivorous and any plants selected
should be resistant to consumption (such as cacti) and non-toxic.
Artificial plants with large leaves may be preferable; avoid those
with small leaves, which may be ingested and result in intestinal
impaction. The effective use of props in a cage will not only
improve the appearance of the enclosure, but may well enhance
the psychological well-being of its inhabitants, and produce
behavior much like that which they exhibit in the wild.

Selecting an Animal
Although Sauromalus ater can be collected with permits across
most of its range, this species is of special concern in many areas,
and I do not recommend obtaining wild-caught specimens.
Fortunately, these lizards are commonly bred in captivity.
Captive-bred individuals are ideal, because wild populations are
not adversely affected and captive-bred animals should be rela-
tively free of diseases and parasites.

When selecting specimens, choose animals that appear
healthy. The base of the tail should be full and rounded. A drawn
appearance is indicative of deficient fat stores or improper nutri-
tion. Legs should be solid and muscular. Individuals should be
bright-eyed, alert, and attentive to activity around them. When
handled, they should not be placid, but rather wiggling around.

A Chuckwalla habitat should be well-structured to provide climbing
space, basking areas, and crevices into which the lizard can wedge itself.
The crevices in the habitat have been created by stacking various types
of cinder blocks to provide spaces of varying size. Photograph by Carole
Saucier.

This captive Sauromalus ater prefers to bask atop the cinder block
structure and sleep in the tightest crevices in the lower block.
Photograph by Carole Saucier. 



Juveniles and most adults will usually inflate their torso to some
degree when handled, as wild animals would in rock crevices. If
these behaviors are not observed, something is probably wrong,
and another animal should be selected.

When considering the acquisition of more than one speci-
men to be housed in a single enclosure, purchase only one male.
Males are territorial and will defend their territories to the detri-
ment of other males in the enclosure. Several females can be
housed with a single male, as long as the caging provides ade-
quate space for the number of animals. Sexing individuals, how-
ever, can be difficult when purchasing very young specimens.
Although adult S. ater are sexually dimorphic, with males much
larger than females, this doesn’t help when dealing with hatch-
lings of the same size. Unfortunately, at this age, no effective way
exists for determining the differences between the sexes, and
probing is not recommended for hatchlings due to the likelihood
of injury. Once lizards reach 6–12 months of age, an accurate

determination of sex is possible. The base of the head in males is
wider than that of females. Also, as males mature, the femoral
pores, located on the undersides of the thighs, become promi-
nent and can be used to reliably ascertain sex. If animals are too
young to use these features and comparing multiple specimens
to one another does not help identify the subtle differences, the
buyer inevitably will be unsure of establishing the proper sex
ratio. If the purchase cannot be delayed until the animals are
older, extra males will need to be removed to a separate enclosure
before they reach sexual maturity.

Lighting
Ultraviolet radiation, specifically ultraviolet B (UVB), must be
provided via either natural sunlight or UVB-emitting bulbs.
Reptiles use UVB to produce vitamin D3 that, in turn, is used to
metabolize calcium (Aucone et al. 2003, Ferguson et al. 2003,
Laing and Fraser 1999, Lian et al. 1999). Without vitamin D3,
bone density can be compromised and this potentially can lead
to metabolic bone disease. Vitamin D3 supplements can be added
to the food, but the amount required is not known, so animals
can easily be over- or undersupplemented. Adequate lighting is
always preferable.

Short of natural sunlight, artificial lights that produce wave-
lengths in the UVB spectrum are the best means for providing
adequate UVB for Chuckwallas in captivity. Chuckwallas can
bask naturally to regulate their vitamin D3 blood levels and body
temperatures. Two bulbs in particular have been shown to pro-
vide enough UVB for proper growth and maintenance: the
Westron Active UV Heat Lamp (Oceanside, New York; Aucone
et al. 2003) and the Zoo-Med Repti-Sun 5.0 fluorescent bulb
(San Luis Obispo, California; W.H. Gehrmann, pers. comm.).
The Active UV Heat Lamp is an incandescent bulb that emits
heat as well as UVB. The UVB will penetrate to 36 in, which is
ideal in larger enclosures. The Repti-Sun 5.0 is a fluorescent bulb,
meaning that additional heat sources will be required. Also, if the
Repti-Sun 5.0 is used, lizards must be able to bask within 8 in of
the bulb in order to assure adequate UVB exposure. Finally, flu-
orescent bulbs should be replaced every six months, as UVB
emission declines dramatically beyond that time. Regardless of
the type of UVB source used, an artificial light cycle should be
set to vary seasonally. In the summer, a 16D:8N (day:night) cycle
is ideal; in the winter, the cycle should be adjusted to 12D:12N,
with appropriate incremental adjustments during fall and spring.

Temperature and Humidity
Chuckwallas are native to desert regions. In captivity, tempera-
tures should mimic those that they would encounter in their nat-
ural habitat. Daytime temperatures should average 80–82 °F
throughout the cage. In addition, a heat lamp should provide a
basking spot of 110–120 °F during the day. This can be either an
Active UV Heat Lamp or an incandescent spot lamp. If an incan-
descent spot lamp is used, also be sure to provide a fluorescent
UVB-emitting bulb (Repti-Sun 5.0). In a large enclosure and if
multiple animals are housed together, more than one basking site
must be provided. Otherwise, dominant individuals will prevent
cagemates from adequately thermoregulating. Temperatures
should drop at night. To follow a reasonably natural cycle during

116 IGUANA  •  VOLUME 11, NUMBER 2  •  JUNE 2004 AUCONE

A healthy male captive Sauromalus hispidus. Note the broad head and
the scales at the back of the head that form small spikes, which are
most prominent in adult males. Photograph by John Binns. 

This female Sauromalus ater was recently received by a rescuer in
Michigan. Its age and history are unknown. Although this individual
is thin, the folds of skin along its sides are normal. Also note the rela-
tively narrow head and that the “spikes” at the back of the head are
barely noticeable. Photograph by Carole Saucier.



IGUANA  •  VOLUME 11, NUMBER 2  •  JUNE 2004 117SAUROMALUS ATER

the summer, nighttime lows should be in the low to mid-70s
(°F); in the winter, temperatures can drop to the low to mid-60s
(°F). Chuckwallas will “hibernate” during the winter if tempera-
tures are allowed to drop to the low to mid 60s (°F) with daytime
temperatures increasing into the 80s (°F) and basking spot(s)
removed.

Humidity in natural Chuckwalla habitat is very low. These
lizards, however, do not seem to be adversely affected by higher
humidity levels. No humidity control should be necessary, even
in naturally humid areas. Residents of arid regions obviously need
not worry about humidity levels.

Diet
Chuckwallas are primarily herbivorous, but may consume live
prey at times. A varied diet consisting primarily of dark greens
should be provided to captive animals on a daily basis (see also
the sidebar on p. 43). Escarole, chicory, dandelions, collards, and
turnip and mustard greens can provide an adequate level of nutri-
tion. This diet can be supplemented sparingly with other leafy
greens, such as romaine lettuce, as well as fruits like apples, pears,
or bananas. When dandelions (or other, but especially yellow
flowers) are blooming, Chuckwallas will happily munch on as
many of them as you can gather. Just be cautious and make sure
that they are collected from areas where pesticides and herbicides
have not been applied. Occasional individuals may take crickets,
wax worms, mealworms, and even pinkie mice, but these should
constitute a very minimal part of the overall diet. Calcium car-

bonate (CaCO3) should be supplemented to the diet once each
week. This is readily available in powdered form and should be
sprinkled over the food to help ensure that enough calcium is
being provided in the diet. Even with adequate UVB lighting,
sufficient dietary calcium is necessary for proper bone growth and
maintenance.

A stable water bowl that cannot be overturned should be
provided. Water should be replaced daily. As a rule, Chuckwallas
get the majority of their water from food, but they will drink
occasionally from a bowl. Adequate water is critical, and a bowl
will provide assurance that an animal can supplement its water
intake as needed.

Reproduction
In captivity, reproduction should coincide with natural seasonal
variations in temperature. A cooling period (or “hibernation”)
during the winter is usually necessary to induce reproductive
activity. After emergence in the spring, males will undertake a
courtship display consisting of a variety of head bobs and
pushups in an effort to induce the females to breed. Following
successful mating, females will deposit eggs approximately 30
days later. In the wild, Chuckwallas lay 5–16 eggs per clutch
(Stebbins 1985). A nest box containing vermiculite, moist sphag-
num, or perlite can be provided, but females also may choose to
lay their eggs under a rock in the enclosure. Any digging activity
should be closely monitored. Eggs can be artificially incubated in
a sealed container of vermiculite mixed with water at a ratio of

Adult male Sauromalus ater, Cataviña, Baja California. Photograph by Brad Hollingsworth. 



118 IGUANA  •  VOLUME 11, NUMBER 2  •  JUNE 2004 AUCONE

0.75:1. The container should be opened twice each week to allow
fresh air to circulate. Eggs should be incubated at 80–82 °F and
will hatch about 90 days after laying.

Juveniles can be housed and fed similarly to the adults.
Multiple males can usually be maintained together until they are
6–12 months of age. At that point, males must be separated, as
aggressive behavior inevitably will increase. If keeping groups of
juveniles together, individuals should be weighed weekly to
ensure that all animals are gaining weight normally. If an indi-
vidual is found to be significantly smaller than companions of
equal age, too many animals may be in the enclosure, resulting
in competition for food and ideal basking spots. Smaller group-
ings may be necessary and undersized individuals must be main-
tained separately.

Conclusion
Chuckwallas are a fascinating species and they can be very
rewarding captives. Private collectors appreciate their relatively
large size and docile personalities. Parameters for keeping this
species are straightforward and, if followed, Chuckwallas can
thrive for many years in a captive environment. With captive
breeding becoming increasingly more commonplace, healthy
individuals are readily available for the home terrarium. However,

as for all reptiles, prospective owners should prepare thoroughly
before acquiring animals. Thought must be given to adequate
housing, because certain conditions must be met before one can
properly care for these unique lizards.

Bibliography and Selected References
Aucone, B., W.H. Gehrmann, G.W. Ferguson, T.C. Chen, and M.F. Holick.

2003. Comparison of two artificial ultraviolet light sources used for
Chuckwalla, Sauromalus obesus, husbandry. Journal of Herpetological
Medicine and Surgery 13: 14–17.

Ferguson, G.W., W.H. Gehrmann, K.B. Karsten, S.H. Hammack, M.
McRae, T.C. Chen, N.P. Lung, and M.F. Holick. 2003. Do Panther
Chameleons bask to regulate endogenous vitamin D3 production?
Physiology and Biochemical Zoology 76: 52–59.

Laing, C.J. and D.R. Fraser. 1999. The vitamin D system in iguanian lizards.
Comparative Biochemistry and Physiology, Part B 123: 373–379.

Lian, J.B., A. Staal, A. van Wijnen, J.L. Stein, and G.S. Stein. 1999. Biologic
and molecular effects of vitamin D on bone, pp. 175–193. In: M.F.
Holick (ed.), Vitamin D-Molecular Biology, Physiology, and Clinical
Applications. Humana Press, Totowa, New Jersey.

Stebbins, R.C. 2003. Western Reptiles and Amphibians. 3rd ed. Houghton
Mifflin Co., New York.

In addition, the following webpage is quite informative:
http://www.reptilesofaz.com/

Sauromalus ater, Isla Tiburón, Sonora. When threatened, Chuckwallas retreat into rocky crevices and fill their lungs with air, expanding the torso
and compressing their body into the crack, preventing extraction by potential predators. Photograph by Brad Hollingsworth. 


