Common Boa Constrictors, Information and Care
Scientific name: Boa constrictor imperator
Other common names: This is the boa subspecies most often encountered in captivity. There are in use a variety of different names all referring to this subspecies, including simply "boa constrictor." This form of boa may be referred to as the pet store boa constrictor, redtail boa, Colombian redtail boa, pet store redtail, and red-tailed boa constrictor.
In fact many common boa constrictors do have a red tail, distinctly different in color than the rest of the body; however, the common name of "red-tailed boa" is also commonly applied to the South American boa constrictor, Boa constrictor constrictor, which typically has an even redder tail.
The common boa has an extensive distribution in nature and many geographic names have come to be used to refer to this subspecies, including; Mexican boa, Sonoran desert boa, Yucatan boa, Central American boa, El Salvador boa, Nicaraguan boa, Panamanian boa, Honduran boa, Hog Island boa, Corn Island boa, and Colombian boa.
Size: This is a relatively slender elongate snake. The head is very distinct from the neck; the body is laterally compressed; the tail is long and strongly prehensile. Large specimens attain considerable bulk and may weigh 40-50 pounds. Adult specimens in most U.S. collections average about 4½-8 feet in total length. The maximum size of this form purportedly approaches 12 feet in total length, but the biggest we have seen were 9-10 feet long.
Distribution: This widespread boa constrictor subspecies occurs on the west coast of Mexico as far north as Hermosillo, Sonora, and on the east coast north to southern Tamaulipas. The species is widespread through the lower elevations of tropical southern Mexico. It is widespread and common in every country in Central America. From eastern Panama the range extends north into Colombia to the Sierra de Santa Marta, and south through coastal Colombia into Ecuador, south as far as Guayaquil. There at the southern extreme of the range, it intergrades with the Tumbes boa, Boa constrictor longicauda and Peruvian coastal boa, Boa constrictor ortonii.
Availability: Wild-caught animals are still collected and exported to the U.S. from several Central American countries, including Guatemala, El Salvador, Nicaragua and Honduras. Wild-bred-captive-born babies also are exported to the U.S., some from Central America and many thousands from northern Colombia. Imported boas are commonly encountered in the pet trade, and occasionally seen at weekend reptile shows.
Boa constrictors have their own following of dedicated keepers and breeders who work with nothing else. U.S. captive-bred animals are readily available. Probably between one and two thousand common boas are now captive-bred and born in the U.S. each year. Excellent captive-bred specimens are available from professional breeders and serious hobbyists.. The species is offered for sale on many price lists, web sites, and classified advertising. Captive-bred animals are often encountered at weekend reptile shows.
Pattern variation: The typical common boa constrictor is a pale snake with a longitudinal series of 20 or more dark transverse bars spaced down the length of the back. These dark bars are each narrowest in the middle of the back and widest at the dorsolateral margin, where they incorporate a pale blotch on each side at the dorsolateral margin.
In some boa constrictor patterns, the dark bars are connected along the sides to form a dark dorsal pattern on the back that outlines pale dorsal blotches that are oval or round. In other patterns, the dark dorsal bars are not connected to other dark elements of pattern.
On the sides are a series of dark blotches with pale centers. Some blotches may contact the dark dorsal pattern. The pale areas of pattern are relatively evenly sprinkled with small black flecks and entire black scales. Generally, the patterns of boa constrictors from Colombia tend to include more bold black scales and even small black blotches on the sides than do the Central American specimens. The ventral surface of the neck and anterior body is ivory or pale gray, on the posterior half of the body the stomach becomes increasingly peppered with black smudges, flecks, and spots.
The tails are pale with large, oval, black-edged red blotches. This pattern continues onto the posterior body where the red pattern becomes more like bands. Continuing forward from the area of the vent, each successive pale interspace becomes wider as each red band becomes more narrow and less red; in this manner the red pattern of the posterior body and tail melds into the dorsal pattern seen on most of the body.
The head is predominantly pale with well-defined dark markings. There may be dark shading or barring on some of pale lip scales. There is a thin dark line on the top of the head from the internasals to the nape of the neck. Some specimens have two small lines over each eye. There is a small dark blotch below each eye and a dark horizontal line through each eye that continues as a well-defined dark postocular stripe.
There are numerous types of anomalous patterns reported to occur in boa constrictors, including a partial or complete loss of dark pattern, a reduction of the amount of dark pattern, or various conditions of dark striping. Some of these conditions have been demonstrated to be inherited as single recessive mutations, while the exact nature of the inheritance of many of the conditions is unknown. Some conditions of reduced dark pattern appear to be inherited as co-dominant traits or possibly as dilutions-more generations of breeding are necessary to determine with certainty the genetic basis of some of the types of patterns.
There are other anomalous conditions of pattern that have been demonstrated to be inheritable, including jungle boas (first bred in Europe), motley boas, first bred by Ron St Pierre of Florida, and arabesque boas, first bred by Steve Hammond.
Color variation: Common boa constrictors are primarily colored in shades of brown. The pale color on the head and most of the body varies from the palest browns, often with yellow or pink highlights, through grayish browns to medium browns. On some snakes the sides of the body are pale silver gray with pink or orange highlights. The dark markings are a rich chocolate brown to brownish black, sometimes with thin black margins. The pale dorsolateral spots are yellowish to ivory white. The pale coloration on the posterior body and tail is typically a medium ivory or pale yellowish tan.
On dark-colored boas the red blotches on the tail and posterior body are typically dark brownish black with scattered dark oxblood-red scales; at the other extreme, the posterior red blotches of beautiful pale boas may be nearly solid bright red with thin black margins
There are numerous reported mutations of color in this population. Several conditions of albinism are known. The best-known lineage of albino boas, first bred by Peter Kahl of Maryland in 1993, is descended from a single wild-bred tyrosinase-negative (t-) albino male brought into the U.S. in the mid 1980s. Another lineage of t- albino boas descended from a different wild-caught female albino, first bred by Brian Sharp of Virginia and known as "Sharp albinos." These two conditions of albinism are apparently due to different mutations, evidenced by the fact that when animals from these two lineages are bred together, the resulting offspring are all normal in appearance.
Another variation of albinism is seen in the VPI caramel-albino lineage. In 1996, two unusual albino boas were serendipitously born in the collection of Becky Hutchins of Texas. These animal and their siblings were acquired by VPI soon after they were born. This boa morph has dark-red eyes, and more color than the Kahl and Sharp albino boas. Areas of black pattern are replaced with a medium purple-gray. The pattern of inheritance of this morph is as a simple recessive mutation, the same as Kahl and Sharp albino morphs.
There are several known wild-caught axanthic boa constrictors, in which the red color of the tail pattern is missing. Captive-breeding through two generations has demonstrated this condition to be inherited in the manner of a simple recessive trait. Peter Kahl was the first to successfully combine one of the axanthic traits with the Kahl albino trait to produce an albino boa with no red coloration for which he has coined the descriptive name "snow boa."
There is a condition of hypomelanism in boas in which the tiny black flecks of melanin are missing, resulting in an overall paler animal. The black margins normally around the dark pattern are absent or greatly reduced, the condition is most obvious around the red blotches on the posterior body and tail. Many of these snakes have significantly reduced amounts of dark pattern. Two Arizona boa breeders, Rich Ihle and Jeff Gee, are primarily responsible for founding the lineages of hypomelanistic boas that are now available.
There is a lineage of unusually red boa constrictors, termed "blood boas, first bred by Ron St. Pierre of Florida. The normal pale brown coloration seen in most boas is replaced with distinctly reddish brown coloration in blood boas.
The motley mutation is both a pattern and color mutation. It is a codominant trait. The super-motley is a solid black patternless snake.
Boa constrictors are exotic and glamorous snakes, and there are few reptile hobbyists over the age of 40 that cannot claim to have possessed at least one boa at some point in their lives. We have had hundreds, and we remain captivated by these beautiful snakes. There is an observable wide variation of color and pattern--at one extreme of the range of variation, boa constrictors can be dark, dusky snakes; at the other extreme, they can be extraordinary pale snakes with pink and orange highlights. Of additional interest to keepers is their moderate size and calm demeanor.
It is this variation in the color and pattern of the common boa constrictors that particularly interests many boa breeders and keepers. Today there are numerous selective breeding projects ongoing, with some dedicated keepers working with third- and forth-generation boa constrictors, attempting to create some new appearance or establish some new mutation of this snake that fascinates them.
-Cage size: Common boa constrictors require a secure well-ventilated cage. A glass aquarium with a secure ventilated top (screen wire or perforated metal) can be a satisfactory cage to display these beautiful snakes. Plastic storage boxes, with numerous perforations for ventilation, can be satisfactorily used to maintain boa constrictors. We raise our young boas to breeding size in 3' x 2' Vision cages. We keep the largest specimens in 4' x 3' Habitat System cages.
We maintain newborn boa constrictors in an enclosure with about 40 square inches of floor space until they are about six months of age.
Young adult boa constrictors are given 2-4 square feet of floor space. Given space and lots of food, common boas grow very quickly to five and six feet in length, and then their rate of growth begins to slow. By four to six years of age, some adult females will require an enclosure with 10-12 square feet of floor space.
-Substrate: It has been our experience and observation that this species does extremely well on either aspen bedding or on newspaper. Both are easy to maintain at a satisfactory level of sanitation. Boas can be successfully maintained on a variety of substrates, including sand, potting soil, clean gravel, or cypress bark chips. HOWEVER, we do not recommend any of those substrates for the average keeper interested in an efficient and easy-to-maintain set-up. Using those substrates, it is difficult to maintain clean cage conditions without excessive diligence.
Boa constrictors of all ages will spend a lot of time climbing and resting up off the floor of the cage if provided with branches or fixed dowels. The laterally compressed body and strongly prehensile tail are physical evidence of arboreal tendencies in this species. However, most boa constrictors are quite happy in a cage set up for a terrestrial snake. Only rarely will some individuals require perches above the floor of the cage in order to feed.
When using newspaper as a cage substrate, it is a good maintenance practice, after papering the bottom, to crumple several pieces of newspaper in the cage, under which the snake can hide if desired.
-Water: Clean water should be available in a glass or ceramic water bowl at all times. We supply young boas with an 8 oz water bowl measuring about 2½" in diameter, 1" in depth. Older snakes have a 16 oz water bowl measuring about 4" in diameter and 2½" in depth. The biggest females have heavy ceramic bowls that hold 64 oz.
Newborn and young pet boas may perch on their water bowls, with one side of their bodies dipped into the water. Even when given a variety of other perches, some snakes may prefer to perch on the water bowl.
Common boa constrictors are rarely observed to sit in their water bowls in conditions of normal health and security. Boas may sit in their water bowls if they are stressed or insecure in their cages (they are "hiding" in their water bowl,) or if they are plagued by an infestation of snake mites.
-Temperatures: As a general starting point, common boa constrictors seem to do best if kept in the low-to-mid-80s degrees F. In fact, it's a good maintenance practice to provide a warmer-than ambient basking spot for boas. This will allow the individual to choose the temperature that best suits at any given time.
Boas like to bask under warm lights or ceramic bulbs. Likewise, they will sit on a warm area of substrate, heated from below with some type of heating pad. Electrically-heated rocks can be very dangerous to boas, as occasionally the surface temperature of some of these hot rocks may exceed 130-140 degrees F and they can cause severe burns on the bellies of unsuspecting boas.
As is true for many snakes, boas can better tolerate temperature extremes if they do not have food in their digestive system. If recently fed, they should not be subjected to temperatures more than 90 degrees F or below 74 degrees F. When empty of food, common boa constrictors are tolerant of a wider range of temperatures.
---Feeding requirements: In captivity, young boas readily eat mice; most readily accept freshly-killed prey offered to them on forceps. That is typically how we feed boas all their lives. Some specimens may eat dead prey left in their cages, but generally this species is not as willing consume dead prey just left in the cage as are some other boas and pythons. Large specimens readily feed on rats. One appropriately-sized rodent per week is an adequate feeding schedule. Adults typically do not feed during the winter months.
Large boas may be fed rabbits. Many boas love to eat chickens, and often boas that refuse to eat rodents will willingly accept an appropriate-sized chicken. Most boas will eat hamsters, gerbils, guinea pigs, and ducks. We know of several iguanas that have been eaten by their boa cagemates. Households with avian pets should be particularly certain that any pet boas do not escape. According to a 1998 news story, an escaped boa ate the neighbor's small dog in California. In spite of this, we have seen several households where the dog and boa lived in some harmony.
An "appropriate-sized" meal is one that makes just a slight lump inside the snake. Snakes that are distended from too-large meals should not be handled.
For their first meals, many newborns will begin feeding on live large fuzzy mice or live pink rats that are simply left in the cages. We feed baby boas only one food item weekly. We do not handle them for two days after they have fed them, if we can avoid it. We make certain to not get them too warm after they have eaten, maintaining them at minimal daily temperature fluctuations of 80-82 degrees F. Once they have begun to feed, most boas subsequently readily accept dead mice as food, either thawed or fresh-killed, but until they are three or four months old, we feed them small prey items.
REMEMBER! A hungry live mouse may attack and damage or even kill a boa if left unsupervised. Don't leave live rodents unsupervised in the cage of any boas. ALWAYS put food for the rodent in the cage.
---Shedding: Common boa constrictors generally have few problems shedding their skin. When a snake incompletely sheds, and a portion of the skin is left adhered to the snake, the snake should be soaked in shallow water or slightly-soapy water for several hours, after which the skin typically comes off very easily.
Small patches of skin that remain adhered to the snake are not expect to have any deleterious effect and it is at the option of the keeper to arrange for the removal. It's probably best to see that skin is not left on the face and eyes. Typically, "stuck" pieces of shed will come off with the next shed. Incomplete sheds and adhered sheds are an indicator that the ambient humidity in the cage is too low and the careful keeper will "tweak" the system to increase the humidity.
---Special considerations for hatchlings and juveniles: When it comes time to get them to feed, newborn boas generally present their keepers with few problems. Youngsters usually shed at 7-10 days of age. We typically wait 2-3 weeks before we feed them, allowing them to utilize the yolk in their bodies. We then offer them live fuzzy mice for their first few meals, simply placing the prey in the cages and letting the babies follow their instincts.
Most common boas are very docile and reluctant to bite. Occasional babies can be snappy, but they are small and the bites are harmless. But when calmly and consistently handled, the youngsters grow to very docile and trusting adults. A lot of biting can be avoided if the babies are not picked up with the hand, but instead are lifted with a small hook (or bent piece of coat-hanger wire) and set in the hand.
Boas undergo an ontogenetic color change as they mature. Newborns typically are grayish-brown. With age the snakes begin to develop more yellow and brown pigment. As boas approach adult size, their colors become more saturated and intense; pink, orange or yellow highlights or iridescence may become visible on the sides of the head and body.
---General comments: Common boa constrictors are among the best snakes to keep in captivity. They are extraordinarily hardy creatures with longevity records in excess of 40 years. They are beautiful, boldly patterned and reasonably priced.
Many keepers do not realize that VPI maintains a large collection of boa constrictors. We have worked with boa constrictors at VPI since 1993. VPI was first to successfully breed albino boas to albino boas. For several years we were the main producer of hypo boas. Today we are working with VPI caramel-albino boas, one of the most beautiful and unique mutations in boas.
Common boas do not attain sufficiently large sizes to present a physical danger to adults, and, to our knowledge, the species has never been responsible for any human fatalities involving constriction. Boas are, none-the-less, relatively large snakes, and in many cities and towns, this species is included in the dangerous animal ordinances. The possession of boas within those municipalities is forbidden or restricted.
Keepers considering this species should carefully consider that the large adults do require relatively large and spacious cages.
Many common boas are remarkably tame snakes, very deliberate in their actions, very alert and aware of their keepers. Years ago, as part of educational demonstrations of snakes, we allowed thousands of strangers to handle trusted common boa constrictors and they never let us down.