by Eileen Underwood and Rebecca Sobol
Originally Published in The Cold Blooded News, V24: 4, Apr., 1997.
Rainbow boas are so named because of the iridescent sheen imparted by microscopic ridges on their scales which act like prisms to refract light into rainbows. They can be found from Costa Rica through central South America in forests, woodlands, plains and swamps. They are primarily nocturnal creatures, sleeping during the day and prowling at night. Rainbow boas range from 3.5 to 7 feet in length and can live for 20 years in captivity.
There are around 9 or 10 subspecies of rainbow boa (Epicrates cenchria ssp.) depending on which source you consult. The most common in captivity are the Brazilian (E.c. cenchria) and the Columbian (E.c. maurus). Other subspecies can be found from time to time. Not all are well defined and various subspecies have been interbred in captivity making identification of unknown subspecies a challenge. Differences are found in color, pattern and size. Juveniles have a very distinct pattern of ocelli which fades with age in some subspecies (e.g., E.c. maurus). The Brazilians (E.c. cenchria) are the largest with a length of around 6 or 7 feet. Even a large Brazilian adult should weigh no more than 10 pounds (4.5 kg). Columbian rainbow boas (E.c. maurus) are typically 5 to 6 feet in length. The smallest subspecies is an undescribed (by taxonomists) subspecies from Guyana (E.c. ssp.),which reaches a length of 3.5 to 4.5 feet. They are a slender boa, so a 6 foot rainbow boa is nowhere near as massive as a 6 foot common boa.
Care of all rainbow boa subspecies is similar although there are minor variations in prefered temperature reflecting temperature variations found through the large range of Epicrates cenchria. It appears that rainbow boas of one subspecies or another can be found anywhere that there is suitable habitat within that range. Since much of this suitable habitat is rather inaccessible, there may be other undescribed subspecies. Several islands off the coast of South America also have rainbow boas, and some subspecies may only occur on one or two islands. See Fogel (1993) for detailed range map.
The primary requirements for an enclosure is that it be large enough to provide the snake with exercise and that it retain heat and humidity. Babies do better in a small enclosure e.g., for first few months a plastic shoe box with holes drilled in the lid, with water dish, hide box and damp paper towels (keep damp, not soaking wet, at all times). If an aquarium is used, it should be no bigger than 10 gallons and part of lid should be covered with plexiglass to keep moisture in.
Adults, on the other hand, like lots of space to roam, so bigger is better. Four to 6 square feet of floor space is recommended for adults. Neodesha brand plastic snake cages have been recommended (Fogel, 1993) with a 36 inch model good for most adults and the 48 inch model for larger (>5feet) specimens. If a glass aquarium is used, a 40 to 50 gallon aquarium with branches to increase usable space is minimal for a single animal. A larger, custom cage would be preferable. They love to climb, so a tall cage with branches for climbing is recommended.
It is generally recommended that rainbow boas be housed individually except during breeding attempts.
Substrates that have been used successfully with rainbow boas include newsprint, paper toweling, repti-bark (orchid bark), cyprus mulch, and Astroturf (high quality, woven-backed). All have in common the ability to retain moisture. A humid-box containing damp sphagnum moss is also recommended. Because of the high humidity (see below), substrate must be changed frequently. Dry moss (lightly misted) can also be used as a substrate.
Temperature preferences vary for different subspecies as they have adapted to different habitats, but all seem to do best when presented with a diurnal temperature cycle (especially if breeding is intended) and a temperature gradient. Brazilian rainbow boas (E.c. cenchria) do best with a nighttime low (NTL) temperature of low to mid 70s and daytime high (DTH) in the upper 80s (total range of 70° to 90°F; (21° to 32°C), with an optimal ambient daytime temperature of 78° to 80°F. Columbian rainbow boas (E.c. maurus) like it warmer, with NTL in high 70s to 80s and DTH of 90° (total range 78° to 90°F) and an optimal ambient daytime temperature of 83° to 85°F. Extended exposure to temperatures over 90°F can kill rainbow boas. It is best to start with a temperature gradient centering around 80°F (range of 75° to 85°F), see where your animal spends most of its time and adjust accordingly. Heat can be provided from a combination of under-tank heat source (heating pad placed under one-third to one-half of the cage) and overhead incandescent light (wattage determined based on size of cage and room temperature).
All rainbow boas are extremely sensitive to dehydration and maintenance of high relative humidity is a must. Cages should be misted several times a day and a humid shelter should be provided. The humid shelter can be in the form of a plastic box with a hole at one end containing moist sphagnum moss. Pools of water large enough for the animal to soak its entire body in should be provided. If the cage has a screen lid it should be partially covered with Plexiglas to help retain humidity. A relative humidity of 75-80% is ideal. Much lower than 50% for extended periods and regurgitation and death by dehydration may result.
Because high relative humidity can encourage mold growth, rainbow boa cages must be kept scrupulously clean, with bedding and moss changed on a regular basis (preferably weekly or whenever soiled).
As mentioned above rainbow boas are very sensitive to dehydration, so drinking water must be available at all times. Additionally, the availability of a bowl of water large enough for the snake to soak in will be beneficial. If placed in the warm end of the enclosure, a “pool” can help raise the relative humidity of the cage. Misting the entire cage several times a day will also help maintain required humidity. Snakes will drink out of any water source present in the cage, so soaking bowls should be kept very clean. Rainbow boas seem to be resistant to “blister disease” and will spend most of their time in moist areas, but a dry area should also be present.
As nocturnal animals, rainbow boas probably do not need or benefit from full spectrum lighting. Incandescent lights can be used to help raise temperature, with white light being used during the day and red light at night. The red light will be lower wattage allowing the preferred drop in temperature at night. Red lighting at night has the added advantage of letting the animals movements be seen without disturbing its day/night cycle with bright light.
Rainbow boas in captivity eat primarily mice and/or small rats. The size of the prey item is determined by the girth of the snake, with the prey being slightly smaller than the widest portion of the snake. It is recommended that only dead food items be offered to prevent injury to the snake. If the snake isn’t hungry, a live mouse wandering around the cage may get bored and start nibbling on the snake. Neonates and juveniles can be fed every week to 10 days, with subadults and adult fed every 10 days to two weeks. Do not overfeed.
Handling and Temperament
Hatchlings tend to be nippy, but with patience and increasing periods of handling they should calm down. Several authors have indicated a wariness and lack of complete trust in rainbow boas, making this boa less of an ideal “pet” snake and not a snake for children to interact with.
Dyce, Justin (1997) The Brazilian Rainbow Boa Home Page. [Online]. Available: http://www.uwm.edu/~dyce/brb.
Fogel, David. (1993) Rainbow boas (Epicrates cenchria). Vivarium 5(2):28-29.
Mehrtens, John M. (1987) Living Snakes of the World. Sterling Publishing Co., Inc. New York.
Peters, James A. and Braulio Orejas-Miranda. (1970) Catalogue of the Neotropical Squamata. Smithsonian Institution, United States National Museum, Washington, D.C. 2 vols.
Ross, M.D., Richard and Marzec, Gerald (1990) The Reproductive Husbandry of Pythons and Boas. Institute for Herpetological Research, PO Box 2227, Stanford, CA 94305.
Schuett, Scott P. (1994) Captive Maintenance and Propagation of the Brazilian Rainbow Boa (Epicrates cenchria cenchria). Reptiles 1(6):32-34.