Boa Constrictor Manual

CHAPTER 1

GENERAL INFORMATION

Boa constrictors are members of the subfamily Boinae in the family Boidae. Like pythons, boas are primitive snakes that have vestigial remnants of the pelvis and hind limbs of their lizard-like ancestors. The cloacal spurs on the sides of the vent, external features that are well developed in male boa constrictors, are connected to these vestigial hind limbs.

Boa constrictors are large snakes with a wide distribution, ranging south from Mexico, through central America and South America, to Argentina. In contrast to pythons, which are egg laying, all boas give birth to live young.

Other Boas

For a long time, boa constrictors were considered monotypic, meaning that they were the only species in the genus Boa, but a recent publication by Kluge suggests that the two species of Malagasy ground boas (Acrantophis dumerili and A. madagascariensis) should be included in the genus Boa along with the Malagasy tree boa (The species Sanzinia madagascariensis would become Boa mandrita). If this seems outrageous to some, I recommend that they first read Kluge's ground-breaking paper and the careful methodology he has applied to reach these conclusions.

A hypomelanistic, "Salmon" phase common boa constrictor. The line was developed by Rich Ihle.

A "Jungle" phase Colombian boa. This new morph was introduced in the U.S. by Pete Kahl.

Scientific Name

To avoid the confusion often caused by common names, most hobbyists use scientific names when referring to amphibians and reptiles. On the bright side, virtually all boa constrictor owners already know the scientific name of the boa constrictor. It is one of the few cases where the common and scientific names are the same: Boa constrictor.

Taxonomy

The number of types of boa constrictors depends on the system of categorization and on the criteria established for recognizing differences. Herpetologists, typically individuals with university training in herpetology, currently recognize one species and between six to ten subspecies. The six species recognized by all herpetologists are:

Common boa constrictor (Boa constrictor imperator)

Red-tailed boa constrictor (B. c. constrictor)

Clouded boa constrictor (B. c. nebulosus)

San Lucia boa constrictor (B. c. orophias)

Short-tailed boa constrictor (B. c. amarali)

Argentine boa constrictor (B. c. occidentalis)

A rare morph of the Crawl Cay common boa constrictor, found on an island off of Belize. It has inconspicuous and reduced tail blotches, and is capable of significant color change. The owner, Tim Mead, reported a litter of twelve from this form.

The following four species are not recognized by all her petologists:

Northwest Peruvian boa constrictor (B. c. ortonii)

Peruvian black-tailed boa constrictor (B. c. longicauda)

Ecuadoran black-bellied boa constrictor (B. c. melanogaster)

Saboga Island boa constrictor (B. c. sabogae)

Protection

All pythons and boas, including boa constrictors, are considered vulnerable by the Convention on the International Trade in Endangered Species (CITES) and listed under Appendix II. This means that those who wish to internationally import or export the animals need special permits. The Argentine boa constrictor is currently listed as endangered by CITES under Appendix I, which means they cannot be exported from Argentina and Paraguay, and that owners require special permits to move captive-bred and long-term captives between countries.

Size

Newborn boa constrictors range from 14 to 22 inches in length and weigh between 2 and 3 ounces. Neonate Colombian boa constrictors are typically around 18 inches in length. Neonate red-tailed boas from Guyana, Surinam, and the Peruvian Amazon basin tend to be larger. The adult size for Colombian boa constrictors is 4 to 9 feet, with occasional specimens reaching or exceeding 11 feet. Adult Hog Island boas (B. c. imperator, Hog Island) typically range from 3 to 5 feet. The largest boa constrictor is the true red-tailed boa (B. c. constrictor) from the Amazon basin of South America, which reaches 12 feet in length. Rare specimens reach up to 14 feet in length. On the other hand, there are areas in the true red-tailed boas range of where the length of adults typically ranges from 4 to 7 feet. The largest boa constrictor on record was red-tail from Trinidad said to have been more than 18 feet long. However, this rumor has been disproved, and researchers think the maximum size for a boa constrictor is probably around 14 feet.

This common boa is double heterozygous for "Ghost" (a cross between hypomelanistic and anerythristic specimens).

Relatively few boa constrictors raised in captivity exceed a weight of 60 pounds, and many of the Colombian boa constrictors and other forms of Boa constrictor imperator do not exceed 30 pounds as adults. I examined a large, healthy female Colombian boa constrictor that measured 10 feet 8 inches and weighed 48 pounds.

Longevity

Boa constrictors are among the longest lived snake species. Reports of boa constrictors living for twenty years or more are fairly common. The oldest specimen on record lived for forty years, three months, and fourteen days at the Philadelphia Zoological Gardens.

Adult boa constrictor longicauda.

Sexing

The easiest way to sex newborn boa constrictors is to attempt to manually evert its hemipenes, which only appear in males. To perform this method, hold the newborn boas so that the hind part of its body is positioned belly side up within your hand. Use your thumb to hold the area just in front of the vent (the opening to the cloaca) against your index finger. Allow the base of the tail (located just past the vent) to rest on your index finger. Then, using a gentle rolling motion and starting at an area about two thirds of an inch past the vent, roll your other thumb toward the vent while applying pressure. If done correctly, this will cause a male boa to evert its hemipenes. If you are not familiar with this process, have an experienced individual demonstrate it for you. Inexperienced keepers can easily injure their snakes by applying too much pressure.

To be sure that you properly sexed your snakes, have your (probable) female boas probed with a 1 mm sexing probe. The probe will reach a depth of two to four subcaudal scales in females, seven to eight subcaudal scales in neonate males, and ten to twelve subcaudal scales in adult males.

Probing is the only way to positively sex adult boa constrictors, but several characteristics, such as the larger body size of females, larger spurs to the sides of the vent in males, and broader thicker tails in males, provide relatively reliable clues to their gender. Breeding behaviors are also very good indicators of the sex of your snakes.

Probing adult boa constrictors is a two-person operation. One individual has to control the snake being probed and firmly hold the vent area of the snake toward the individual performing the probing (belly side up). To help control large snakes and facilitate probing, put the snake in a cloth snake bag, allowing only the tail to remain outside. For adult boa constrictors, use 2 to 4 mm probes, depending on the size of the snakes.

A short-tailed boa constrictor.

An Argentine black-tailed boa.

To probe a boa constrictor, hold the area just in front of the vent with one hand, and use your thumb to pull back the area in front (towards the head) of the anal scale to expose the cloacal opening. After moistening the probe with clean water, gently insert the probe into one of two small openings visible to the side of the cloacal opening with your other hand; use a slight twirling motion. In adult females, the probe will enter a musk gland to a length of two to four subcaudal scales, while in adult males, it will enter an inverted hemipenis to a length of ten to twelve subcaudal scales. To verify a reading, repeat the process on the other side. This is a procedure is best performed and taught by experienced individuals. Most specialized reptile dealers will perform this service when you intend to buy animals of specific sexes.

Diet and Growth

It is difficult to present a typical growth pattern for boa constrictors, because their growth rate is affected by their sub-species, population characteristics, individual characteristics, the temperature of their enclosure, and their feeding regimen. In addition, published information on this subject is of marginal value because species are frequently misnamed or improperly categorized.

The popular Colombian boa constrictor originated west of the Andes. Most specimens in the pet trade were collected from an area known as the Magdalena River Valley, and shipped out of Baranquilla.

In a very broad sense, the growth pattern demonstrated by Colombian boas and red-tailed boas is as follows:

From newborn to twelve months: Most specimens grow 3 to 4 feet in length, though some Colombian boa constrictors can grow to nearly 5 feet, and a few individuals reach almost 6 feet during that period of time.

From twelve to twenty-four months: Typical specimens range from to 4 to 7 feet in length, though some reach a length of 8 feet, and some individuals occasionally reach nearly 9 feet. As a general rule, B. c. imperator from Colombia are the fastest growing boa constrictors. True red-tailed boas tend to grow at a...