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IGUANA  •  VOLUME 13, NUMBER 1  •  MARCH 2006 37CORALLUS CANINUS

Ranging widely across northern and central South America,
with the largest known range of any currently recognized

species of boid on earth, the Emerald Tree Boa (Corallus cani-
nus) is among the most recognizable species in herpetoculture.
Although broadly distributed, the species is nowhere common
and, given the absence of empirical data to the contrary, we can
only assume that population numbers are equivalent to those of
the past.

Corallus caninus has long been a barometer species for biol-
ogists concerned with the ecological conditions in its natural
environment. Today, the species also can be seen as an indicator
of how improvements in the basic understanding of the species
and the development of specific tactical skills have led to dra-
matic advances in herpetoculture.

Secretive, totally arboreal, nocturnal, sometimes irascible,
and armed with a formidable array of weaponry, Emeralds were
long considered a hands-off species fit only for professional zool-
ogists. For decades, the species remained widely misunderstood.
As eye-catching disposable acquisitions, they were used in the
pet trade largely as an attention-getting loss leader, a fact that led
to the premature death of many thousands of imported speci-
mens. Today, C. caninus is considered one of the pinnacles of
modern herpetoculture. The same refinements in husbandry
practices that have led to similar successes with other challeng-
ing species provide a bright and optimistic future for the
Emerald Tree Boa in captivity.

With this two-part article, I present methods honed by
years of observation and practical experience. These should give
anyone considering the acquisition of this fascinating species a
sound basis on which to build his or her own practical strategy
for success. This first installment will provide a conceptual
preparation and housing considerations. Part two will present
sound acquisition strategies along with the more technical
aspects of husbandry and propagation, as well as a glimpse at
some of the empirical data from which the suggested strategies
were formulated.

INTRODUCTION
Once the decision to keep Emeralds has been made, the best
chances for success hinge on solid preparations. These prepara-
tions are designed to minimize the stress for keeper and the kept
in order to assure a smooth and pleasurable transition for both.

In nature, Emeralds are exclusively arboreal primary rain-
forest dwellers that thrive within a relatively narrow range of con-
ditions. Until recently, this combination was quite challenging to
recreate within a captive environment. Maintaining moderate
ambient heat, high relative humidity (RH), and continuous air
circulation was difficult enough, but attempting to balance these
elements to within the specifications of a Neotropical rainforest
habitat have traditionally proven all but impossible for the aver-
age herpetoculturist. As a result, even today, appropriate captive
habitats are still relatively uncommon. Interestingly, however,
long before the advent of hi-tech gadgetry, horticulturists had

H U S B A N D R Y

Emerald Gems (Corallus caninus): 
Captive Husbandry and Propagation

Part I: Introduction and Habitats
Joseph M. Polanco

Photographs by the author except where indicated.

The extent, continuity, and pattern of white markings in Corallus can-
inus vary considerably in different parts of the species’ natural range
(see also Iguana 12:2–7).

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refined techniques for the maintenance of precise atmospheric
conditions in greenhouses, and these same strategies can be suc-
cessfully applied to housing C. caninus.

HABITAT: ACQUISITION 
AND PREPARATION

Setting up an environment that reliably mimics conditions in
the wild will minimize the stress involved in adapting your
acquisition to a new habitat. The key ingredients — tempera-
ture, humidity, and air circulation — need to be brought into
balance and proven to be continuously sustainable (around-the-
clock and throughout the year) prior to the introduction of any
inhabitant.

Habitat selection is largely a matter of personal taste and
practical affordability. Although many types of caging exist, some
materials are better suited to housing this species than others.

Plastics, such as acrylic and PVC, are ideal caging media in
which to house tropical species. Aside from being impervious to
the ravages of moisture, these materials also are able to withstand
the stresses of expansion and contraction resulting from con-
stantly changing temperatures. Additionally, many plastics are
lightweight, and most forms are quite durable and easily cus-
tomized. The latter quality is invaluable when making adjust-
ments to fine-tune a newly acquired habitat. Some plastic habi-
tats offer exceptional visibility. Others are virtually indestructible,
but still manage to remain feather light. All in all, given the myr-
iad forms and practical applications, plastics are the material best
suited to the task both aesthetically and in terms of cost and
availability.

Glass enclosures have long been an industry standard, pro-
viding keepers with the advantages of high visibility and invul-
nerability to moisture. These too are available commercially in
a variety of styles and budget categories. However, glass has the
disadvantages of being relatively heavy, less durable than plastics,
and more difficult to maintain and to customize.

Wooden and melamine enclosures, while both popular in
general herpetoculture, are less practical for use with tropical
species. Extensive moisture proofing of all unsealed interior sur-
faces, including joints, access ports, and vents is a necessity for
those wishing to utilize these materials. Wood, being inherently
hygroscopic (readily absorbing moisture), attracts and absorbs
moisture much like a sponge. Even when covered in melamine,
moisture will seep into joints, finding any chink in a unit’s
waterproofing. Once absorbed by the unprotected wood, mois-
ture causes damage via swelling, and deformity, and ultimately
rots the unit. Additionally, the relatively high weights of these
materials combined with their extreme vulnerability to the fluc-
tuations in temperature and humidity required by tropical
species are serious disadvantages that offset the benefits of low
initial cost and high customizability.

Practical considerations useful in assessing the desirability
of a particular unit are its overall dimensions, visibility, accessi-
bility, and ventilation and thermal properties.
• Dimensions: Corallus caninus requires little actual space in

which to reside. Vertical space should be the primary consid-
eration when evaluating possible caging. Large adult speci-
mens rarely exceed 2 m in length, and even these rare giants
can be comfortably housed in units with as little as 30% of
their body length in height. However, any enclosure should
be of sufficient volume to allow for perching at different lev-
els, as this metabolically slow species requires nightly exercise
in order to optimize its digestive processes. An average 1.8 m-
long adult will be completely comfortable in a unit measur-
ing 45 x 45 x 65 cm (approximately 18 x 18 x 25 in, with the
greatest dimension in height).

• Visibility: The day/night cycle within the Neotropical range
of C. caninus varies little, and a year-round 12/12 formula will
fulfill the species’ physiological needs. Enclosures constructed
of opaque materials may require in-cage lighting if ambient
illumination is inadequate. Some cage designs provide
screened openings for above-cage lighting and heating, but
such openings sacrifice some degree of heat and moisture
retention. Such units generally require modification in order

38 IGUANA  •  VOLUME 13, NUMBER 1  •  MARCH 2006 POLANCO

Facility for housing Emerald Tree Boas showing vented enclosures,
external lights, and pullout trays for easy maintenance.

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Facility for housing Emerald Tree Boas showing tall cages with large
openings that allow ready access for maintenance. Note the humidifier
in the foreground; controlling the environment of an entire room pre-
cludes the duplication of control mechanisms for each enclosure.

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IGUANA  •  VOLUME 13, NUMBER 1  •  MARCH 2006 39CORALLUS CANINUS

to keep temperature and humidity levels within acceptable
limits.

• Accessibility: Cleanliness is of utmost importance when deal-
ing with tropical habitats. Fortunately, C. caninus is a very
low-maintenance form when compared to many other com-
monly kept species. Nevertheless, ease of maintenance should
be evaluated seriously, especially for those planning on hous-
ing larger numbers of animals. Ideal units will have large
openings that provide unobstructed access to any part of the
interior. Fixtures such as perches and substrates should be eas-
ily accessible, and preferably removable. Slide-out substrate
trays provide for easy removal of water bowls and other cage
furnishings with a minimum of disturbance to the unit’s
inhabitant.

• Ventilation: Proper air circulation is crucial to maintaining a
balanced tropical habitat. Too little exchange results in con-
densation, mold, and bacterial growth, whereas too high a rate
may prevent adequate humidification and lead to respiratory
issues and dysecdysis (shedding problems). The ability to eas-
ily modify a selected unit becomes most apparent in this con-
text; the ventilation rule-of-thumb is that “the greater the
inherent difficulty of modifying a unit, the greater the initial
need for more than ample ventilation.” Restricting airflow is
always easier than creating it; therefore, glass units may need
a vent as large as an entire exterior surface plane in order to
assure proper airflow. Units with the best design actively uti-
lize thermodynamics to provide a proper balance. Some units
achieve this by virtue of their physical design, whereas others
employ a system of fans, vents, and dampers. While both
methods are effective, the latter is generally more versatile and
better suited to a wider range of applications.

• Thermal Properties: The thermodynamic properties (rela-
tionship between heat and other forms of energy, in this case,
air circulation) of a unit are largely determined by the place-
ment of ventilation ports. Thermal gradients are essential in
creating dynamic airflow as well as assuring a comfort zone
for a unit’s inhabitant. Because heated air rises, most units are
provided with top or high-level exhaust vents. However,
equally important is the supply vent through which fresh,
cooler air will find its way into a unit. These “supply vents”
should be located at lower levels of the unit. Ideally, both the
supply and exhaust ports will be equipped with a damper.

Once a unit has been selected, the next step is to consider the
basic elements that will become a permanent part of the envi-
ronment. Appropriate hardware elements will be functional and
durable. Environmental controllers, fans, humidifiers, heat
sources, lights, water bowls, perches, and even substrate materi-
als and cover vegetation should all be given the same degree of
earnest consideration previously focused on unit selection.

Whereas aesthetic considerations will influence the selec-
tion of cage furnishings to some degree, the most ergonomically
efficient minimalist designs require less of virtually everything.
Focusing on the inhabitant as the primary attraction and mini-
mizing the number of decorative items will minimize mainte-
nance time and allow for greater budget flexibility, especially
when considering larger colonies.

By contrast, naturalistic enclosures mimicking the natural
environment of the occupants provide stunning visual displays
that enhance interest and promote an appreciation for the
beauty and symbiotic nature of the species and its natural habi-
tat. However, each additional layer of complexity in design adds
to the level of maintenance required for both the inhabitant and
the habitat to remain in optimal health.

Depending on the nature of the facility, minimalist habi-
tats within environmentally controlled rooms may consist of as
little as two perches and a water source. Although such setups
have proven ideal and are commonly parts of larger collections,
the majority of herpetoculturists employ environmentally inde-
pendent self-contained habitats. Such units require additional
hardware to achieve and sustain the continuous levels of tem-
perature and humidity necessary to maintain Neotropical

Adult male Corallus caninus demonstrating the color and “personality”
that causes these snakes to be so prized by hobbyists.

Adult male Corallus caninus showing the slit pupils associated with noc-
turnal activity, the heat-sensitive pits that locate prey and direct strikes
even in the absence of light, and the characteristic posture assumed by
Emerald Tree Boas.

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species. The use of either interior heating devices, such as radi-
ant heat panels, or external heat sources, such as ceramic heaters,
bulbs, or under-cage heating pads, are common. Of necessity,
this type of equipment must be regulated. Thermostats,
hygrostats, or the simple regulation of voltages via analog
rheostats are all in common use, and all are known to be effec-
tive, although the latter is a far less reliable option.

Initial acquisition of only the most basic essentials is a cost-
effective and flexible position from which to begin testing the
environmental properties of a chosen habitat. Limiting initial
purchases to just these items allows for options to be considered
as specific need arises, as opposed to committing oneself to as
yet unproven combinations.

For example, one might begin with the acquisition of an
enclosure, a radiant heat panel, and a proportional thermostat.
After setting up the unit including any proposed cage furnish-
ings, one can begin to stabilize the environment to within the
tolerances recommended for the species. A target range of 29 ±
1 °C at 65 ± 5% RH (the maintenance section in part II of this
article will provide a full breakdown of the seasonal climatic
cycles) stably maintained on a round-the-clock basis under both
lighted and unlighted conditions is optimal. If temperatures
within a unit are adequate but humidity levels are too low (the
most commonly encountered situation), one can consider
options for augmenting the RH according to the nature of the
habitat. The addition of an under-cage heating unit (Flexwatt,
heat tape, heating pads) will help raise RH levels in any config-
uration in which water or a water container comes into contact
with the cage floor or substrate. An ideal balance occurs when
the under-cage heater is controlled by the same controller used
to regulate the radiant heat panel, although this is not always
possible. Air stones, foggers, waterfalls, and even full-blown
automated misting systems are all proven options for raising RH
levels. Various alternatives in all of these categories are commer-
cially available and limited by the usual constraints of aesthetics
and budget.

40 IGUANA  •  VOLUME 13, NUMBER 1  •  MARCH 2006 POLANCO

A naturalistic enclosure for housing an Emerald Tree Boa; note the low
air intake, high vent, and large water bowl.

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Naturalistic enclosures can be striking, but the inhabitant is often less
evident than in minimalist enclosures.

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Naturalistic enclosures can provide a sense of the interactions that
occur between a tropical snake and its natural environment.

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Complex naturalistic enclosures require considerably more maintenance
than minimalist habitats; prospective snake owners should consider the
extra time and effort required before committing to such an endeavor.

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IGUANA  •  VOLUME 13, NUMBER 1  •  MARCH 2006 41CORALLUS CANINUS

Another common scenario involves the formation of exces-
sive levels of visible condensation when temperatures and
humidity are sustained within the optimal range. In order to
solve this problem, a basic understanding of why condensation
forms is necessary. Warmer air is able to hold a greater amount
of moisture than cooler air. When warm, moist, slow-moving
air inside an enclosure comes into contact with a relatively cool
surface (such as the walls of the enclosure), it begins to cool.
Once that air cools below its capacity to hold its current mois-
ture load, it “gives up the excess” in the form of condensation
that subsequently forms on the cooler surfaces. Since reducing
the overall RH below Neotropical standards is not an acceptable
option, in order to prevent condensation, air circulation must
be increased. Augmenting the movement/exchange rate of air
within the enclosure decreases the amount of time that any par-
ticular air mass is in contact with the afore-mentioned cooler
surfaces. This reduced contact translates into a reduction in cool-
ing and an increase in the evaporation rate within the enclosure,
thereby decreasing the formation of condensation.

Air circulation within a habitat can be enhanced in many
ways. These options, once again, are limited by considerations
of aesthetics and affordability. The use of external ventilators,
such as reciprocating fans or individual unit-specific exhaust fans
(computer case fans are a commonly employed solution), is an
extremely efficient and cost-effective strategy. Habitat modifica-
tions that enhance the thermodynamic properties of a unit, such
as the introduction of additional venting or the augmentation
of existing vents with dampers, is likewise effective. In some
cases, simply modifying or adjusting the balance or manner in
which internal/external heat is applied (because warmer air rises,
a reduction in heat at the upper levels of a cage will cause the
warmed air at the bottom of an enclosure to rise and seek to
escape, resulting in increased circulation) can be a very effective
form of thermodynamic modification.

Once construction and setup have been completed and a
habitat has been fully stabilized, the most time-consuming and
nearly all of the most demanding work has been done.
Successfully accomplishing this goal prior to the acquisition of an
actual animal will give you the best possible chance of keeping
your prized acquisition in peak condition. In the next installment,
I discuss how to acquire a healthy specimen and specifically how
to go about giving it exactly what it requires throughout its life to
thrive and even reproduce. I think you’ll be pleasantly surprised at
just how little actual work is required — once you’ve completed
the tasks that we covered in this installment.

Acknowledgements
My thanks go out to John Benz, Rolando Burgos, Stan Chiras,
Craig and Karen Clark, Frank Fusaro, Robert Henderson, John
Martin, Al Montejo, Tony Nicoli, and the entire online Corallus
community of readers and participants at http://www.thetree-
boaforum.com for supplying and sharing their pictures, empirical
data, anecdotal accounts, and tremendous passion for this species.

Minimalist enclosures work well and are easily maintained.

Easily modified, lightweight plastic enclosures with perches at several
heights facilitate maintenance of proper temperature and humidity.

Minimalist enclosures appropriately emphasize the inhabitant.

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