Iguana 13.2 b&w text IGUANA • VOLUME 13, NUMBER 2 • JUNE 2006 133CORALLUS CANINUS With the largest known range of any currently recognized species of boid and a fascinating and beautiful variety of morphologies, one might logically assume that the Emerald Tree Boa (Corallus caninus) would be among the most recognizable and widely kept species in herpetoculture. However, it is only recently that a broader understanding of the species has enabled prospec- tive keepers to adapt and develop the environmental regimes nec- essary for this highly specialized snake to thrive in captivity. The first installment (Iguana 13(1): 37–41) proposed a set of guidelines for the acquisition and preparation of enclosures appropriate for housing the species. Part II presents one sound strategy for the acquisition of healthy, viable specimens as well as some of the more technical details associated with husbandry. INTRODUCTION Preparation and forethought equal to that employed during the conceptualization, procurement, and setup of the enclosure should now be addressed to acquiring a snake. One of the best resources for today’s herpetoculturists is the internet. This inter- active knowledge base provides access to reams of information, anecdotal experiences, and live response forums linking new keepers with those who have already had success with Emerald Tree Boas. Judicious use of the internet can help prospective keepers form realistic expectations, minimize the likelihood of unpleasant surprises, and provide a generous sounding board for those actively seeking answers to specific questions. Researchers involved primarily with species classification and the study of natural history have long benefited from the publication and dis- semination of scientific information. The information-sharing capabilities of the internet have resulted in an exponential increase in interest and success for herpetoculturists involved with the captive husbandry of this and other species. SPECIMEN ACQUISITION As with habitat selection, personal taste and practical affordabil- ity are important factors during the selection of an animal. The uninitiated often tend to overlook the subtleties that differenti- ate individuals within any given species. For C. caninus, this can H U S B A N D R Y Emerald Gems (Corallus caninus): Captive Husbandry and Propagation Part II: Acquisition, Maintenance, and Diet Joseph M. Polanco Photographs by the author. Prospective purchase of an Emerald Treeboa (Corallus caninus) should only be considered when the snake’s outward physical appearance con- forms to criteria established for robust, healthy animals. A healthy Emerald Treeboa (Corallus caninus) is robust, unblemished, brightly colored, and active, coiling tightly on elevated perches and responding quickly to stimuli. Iguana 13.2 b&w text.QX6 6/26/06 1:20 PM Page 133 lead to an “all emeralds are more or less equal” mindset, which may place too much weight on the physical beauty of an indi- vidual specimen. This is one of the most common mistakes first- time keepers are likely to make. As with icebergs, within the Corallus complex, what lurks beneath the surface is what needs to be evaluated in order to make a wise decision. The tempera- ment and physical condition of animals available on the open market varies widely and individuals inexperienced with the species do not have the odds in their favor. Wild-caught animals, especially those that have not been in a stable, controlled envi- ronment for a minimum of one year, should never be consid- ered by any but the most seasoned of veterans. Acclimating wild-caught treeboas is no simple undertaking. Any reputable dealer, even those with years of experience, will tell you that the mortality rate of imported specimens of this species is appallingly high. Statistics indicate that more than 50% of captives of all ages die during the first year. For those specimens that do survive the initial acclimation period, chances of survival in the long term (> three years) are equally grim. Although I have not been able to collect empirical data, my own numbers reflect a survival rate of just over 65% for adult tree- boas and just over 70% for animals acquired prior to their onto- genetic change. Therefore, as a rule, only captive-born and bred specimens (subsequently referred to as CBB), purchased from well-estab- lished, reputable sources should be considered. Where C. cani- nus is concerned, “impulse buying” more often than not leads to an unfortunate experience. Morphological conformation notwithstanding, prospective acquisitions should only be con- sidered if and when their outward physical appearance conforms to the criteria describing a robust, healthy animal. Animals that appear skinny, dehydrated, blemished, dull, sluggish, or gaping, or those that are loosely coiled or not perched at all should be dismissed out of hand. For the purposes of this article I will restrict all future references and recommendations to those appli- cable to CBB specimens. The above-mentioned physical conditions are often symp- tomatic of a variety of potentially serious pathologies. One of the few true challenges associated with this species is that even the most common ailments are often difficult to detect. Devoid of compassion or sympathy for the infirm, nature provides many species, including C. caninus, with the instinct to mask illness. Emeralds are so adept at this practice that by the time a prob- lem becomes obvious the individual is often beyond salvage. For this reason, animals with a history of illness, however minor, should be dismissed from consideration. The previously mentioned statistics largely reflect the more commonly available “Northern” variety of the species. Although susceptible to the same maladies, stress-related illnesses, and par- asitic infestations, the Amazon Basin variety appears to benefit from two factors that may be largely responsible for the differ- ences seen between the two populations. First, the Basin form is widely believed by those intimately familiar with both varieties to be hardier and more resilient. Although this disparity itself is undocumented and remains largely unexplained, one popular belief is that this form’s larger geographic distribution has pro- vided for an inherently wider set of environmental tolerances. The other more prosaic factor has been the lack of ready avail- ability of Basins to the export trade. Local restrictions and the logistical challenges associated with their collection have kept the exported numbers of Basins very low for over three decades and the prices charged for these rarely seen but highly prized exports have tended to be very high. With the laws of supply and demand keeping prices high, improved care at every stage of the importation process provides better returns for importers. Currently, a relatively strong U.S. community of well known, reputable breeders is involved with the propagation and sale of both Northern and Basin varieties. On the whole, these 134 IGUANA • VOLUME 13, NUMBER 2 • JUNE 2006 POLANCO Wild-caught animals, especially those that have not been in a stable, controlled environment for a minimum period of one full year, should never be considered by any but the most seasoned of veterans. This individual, although superficially healthy, was dead on arrival at the facilities of a dealer in tropical reptiles. Blister disease can be debilitating; acquiring an animal with the intent of nursing it back to health is a bad idea, even for an experienced keeper. Iguana 13.2 b&w text.QX6 6/26/06 1:20 PM Page 134 IGUANA • VOLUME 13, NUMBER 2 • JUNE 2006 135CORALLUS CANINUS individuals happily offer support and guidance before, during, and sometimes after the sale. This type of networking acts as an invaluable safety net for those interested in keeping this species. By availing themselves of the knowledge and experiences of oth- ers, prospective keepers are able to tip the scales steeply in their favor, drastically reducing the duration of the C. caninus learn- ing curve. Husbandry Basics The essentials of effectively keeping C. caninus in captivity can be broken down into three categories: environment, diet, and record keeping. The first installment discussed the importance of stabilizing environmental factors prior to the introduction of a live animal. Although C. caninus is not an overly delicate species, keepers can be quickly overwhelmed with health issues when tolerances are violated. Until such time as accurate DNA-profiles of the species allow for a classification by which herpetologists can identify and differentiate individual populations, accurately fine-tuning indi- vidual environmental variables to specific animals remains impossible. Locality data on imported specimens are non-exis- tent, and morphological differentiation is far too imprecise to provide even the most remote hope of accuracy. Therefore, today’s Emerald specialists have chosen to employ a range of temperature and humidity standards derived from averages gath- ered from across the entire range of the species. Tables 1 & 2 list average temperature and relative humidity levels from across the species’ natural range for periods ranging from 4–23 years. I have derived the following environmental maintenance schedule from these data. Averaging the recorded temperature data and buffering them by 4 °F toward the median, provides a temperature range within which any individual, regardless of geographic origin, can thrive. Recommended daytime high and nighttime low temperatures for captive C. caninus should be 84 °F (DTHT) and 74 °F (NTLT), respectively. Although some keepers use the same data to regulate rela- tive humidity (RH) levels, years of experimentation have led me to depart from levels found in the wild. Table 2 reflects daytime relative humidity highs (DTRH) and nighttime relative humid- ity lows (NTRH) averaged from eleven locations across the species’ range. The data from which these averages were derived were collected over periods from 2–21 years. The reason I choose to deviate from these natural averages is the negative effect of sustaining such high RH levels within enclosures. Without the natural cleansing processes found in nature, black molds tend to grow in very high concentrations. These molds produce spores that become air-born and eventually settle on and adhere to every porous surface in an enclosed habitat. Even over relatively short periods, such concentrations present an unnaturally high risk of infection or allergic reactions for both snakes and human handlers. Therefore, over the years, I have adopted modified RH lev- els that have proven completely adequate, enabling me to main- The “Northern” variety of Corallus caninus (left; this animal is from Suriname) is more commonly available, although the Amazon Basin variety (right) appears to be hardier and more resilient. Table 1. Temperature (°F) and precipitation (inches) averages across the range of Corallus caninus. Portions of the species’ range are indicated by N (= north), S (= south), E (= east), and W (= west). RF = rainfall. Area JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC N-Hi 86 86 87 88 87 88 89 90 92 92 90 87 N-Lo 72 72 72 73 74 73 73 74 74 74 74 73 RF 8.2 5.6 6.1 8.4 11.7 11.7 9.1 7.0 3.6 3.6 4.8 7.4 S-Hi 91 91 90 90 88 88 90 92 93 93 91 90 S-Lo 72 73 72 70 66 63 61 64 69 72 72 73 RF 10.0 8.6 8.1 4.0 2.2 0.5 0.3 1.1 1.8 5.2 6.0 8.1 E-Hi 87 86 86 87 88 89 88 89 90 90 90 90 E-Lo 76 76 75 75 75 75 75 75 76 76 77 77 RF 10.5 10.0 11.8 12.0 10.5 8.2 6.4 6.5 7.5 9.1 9.8 10.2 W-Hi 88 87 87 87 86 85 85 87 88 88 88 88 W-Lo 73 73 73 73 73 72 71 72 72 72 73 73 RF 10.5 10.0 11.8 11.9 10.5 8.2 6.4 6.5 7.5 9.1 9.8 10.2 Iguana 13.2 b&w text.QX6 6/26/06 1:20 PM Page 135 tain a healthy population of tropical species while minimizing the excessive formation of fungal pathogens. While actual RH num- bers for each individual facility will vary according to the funda- mental variables of area versus air circulation, DTRH levels from 65–75% and NTRH levels from 45–55% have proven ideal. Diet Like that of most opportunistic ambush predators, the natural prey of C. caninus in the wild is known to vary widely. For the purposes of captive maintenance, we deal with three major sources of nutrition, all rodents. Rats, mice, and Siberian Dwarf Hamsters are most commonly used. Each species may be fed at various stages of a snake’s development. I use the following guidelines in my facility (species may vary, but approximate sizes should be watched closely): • Siberian Dwarf Hamsters (live crawlers, ± 8 g): Initiating the natural feeding response in neonate snakes. • Pink rats (live or frozen/thawed, ± 8 g): Neonate maintenance once a solid feeding response has been established. • Fuzzy rats (frozen/thawed, ± 16 g): Neonates > 60 g. • Rat pups (frozen/thawed, ± 25 g): Yearling snakes > 200 g. • Weanling rats (frozen/thawed, ± 35 g): Two-year old snakes > 350g. • Small rats (frozen/thawed, ± 75 g): Sub-adults > 500 g. • Medium rats (frozen/thawed, ± 150 g): Adult animals > 900 g. • Large rats (frozen/thawed, ± 250 g): Adult females > 1500 g. In an effort to promote optimum fitness while avoiding obesity, which may shorten lifespan and reduce reproductive productivity, feeding schedules and maintenance records on every individual should be meticulously maintained. Such records are a crucial tool in managing these snakes, given their naturally low activity levels, which, exacerbated by captivity, are susceptible to a number of GI- related maladies. Avoiding these illnesses is relatively easy, given the proper tools and understanding their use. Feeding frequency at my facility varies according to age and sex. Younger specimens are fed most frequently, on a 10–14-day schedule from 30 days until approximately eight months of age. The latter frequently coincides with ontogenesis, which is signi- fied in C. caninus by a change in ground color from neonatal red, green, or yellow to the familiar adult shade of green. However, this change, which is itself an energy-related process, is not inherently tied to age. Neonates whose GI tracts are fully engaged at an early age, process meals and eliminate wastes on a fairly regular, predictable schedule. Such individuals will benefit from being kept on a 10- day feeding interval. Animals with tendencies to process meals less quickly should be held to a longer 14-day period. Under no 136 IGUANA • VOLUME 13, NUMBER 2 • JUNE 2006 POLANCO Frozen food size references. Live Siberian Dwarf Hamster (crawler) with dime for size reference. Table 2. Relative humidity table (%) averaged from across the entire range of Corallus caninus. DTRH = daytime relative humid- ity highs; NTRH = nighttime relative humidity lows. JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC DTRH 94 94 94 95 95 93 92 91 91 91 91 93 NTRH 76 78 77 78 77 72 68 66 66 67 70 76 An 18-month-old Corallus caninus on a scale for size reference. Iguana 13.2 b&w text.QX6 6/26/06 1:20 PM Page 136 circumstances should a neonate be fed more than two meals without a bowel movement. A majority of neonates will elimi- nate the waste products from its previous meal within a few days. This waste is literally being moved out in order to make room for the wastes generated by the digestion of newly ingested prey. Should an animal take two meals and fail to produce a bowel movement, one should induce elimination. This can be most easily accomplished by encouraging simple exercise on approximately day eight following the second meal. Allowing the animal to crawl freely over one’s open fingers from hand to hand for a period of ten minutes is usually enough to produce the desired result within hours of the session. For animals from 8 months to three years of age, a 14-day interval between meals is appropriate. From this stage forward, no individual should be given more than three meals between bowel movements. Once an animal has begun eating small rats weighing > 75 g, feeding frequency can be reduced from 14 to 18 or even 21 days. Females can remain on this schedule, but males, having reached sexual maturity (at approximately four years of age) should be shifted to a monthly feeding routine. The one exception to these adult feeding schedules is made in prepa- ration for breeding. Because cessation of feeding is common for both males and females during different stages of the breeding process, “padding” the energy reserves of both during the weeks prior to the onset of the breeding season is prudent. For animals slated for breeding in a given calendar year, I reduce the num- ber of days between feedings to the shortest periods mentioned previously for their respective sexes. Males will be fed (offered food) every 21 days and females every 18 days beginning 60 days prior to introductions and lasting throughout the entire breeding season. Many males will lose interest in feeding shortly after an initial introduction and may not feed again for the rest of the season. By contrast, females will usually feed ravenously throughout the season and stop only after ovulation. Occasionally, males that are not actively breeding will also stop feeding during this period. For this reason, sexually mature, non-actively breeding males should be removed from the imme- diate area in which breeding pairs are being housed. Acknowledgments For general help and sharing of information over the years, and for this particular project as well, I thank 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.thetreeboaforum.com. Your passion inspires and pushes the work forward. References Henderson, R.W. 1993. Corallus caninus. Catalogue of American Amphibians and Reptiles (574): 1–4. Stafford, P.J. and R.W. Henderson. 1996. Kaleidoscopic Tree Boas: The Genus Corallus of Tropical America. Krieger Publishing Co., Malabar, Florida. Adult animals should receive food commensurate with their size; in this instance, an adult female boa consumes a large rat. IGUANA • VOLUME 13, NUMBER 2 • JUNE 2006 137CORALLUS CANINUS Highly arboreal treeboas rarely descend from elevated perches, even to consume large prey. Iguana 13.2 b&w text.QX6 6/26/06 1:20 PM Page 137