Boa constrictor

Though all boids are indeed constrictors, only Boa constrictor (and its subspecies) is commonly referred to, in English, as a boa constrictor—an example of a species being referred to colloquially using its scientific binomial name. The species and subspecies of B. constrictor are part of a variable, diverse group of New World boids referred to as "red-tailed" boas, comprising the species Boa constrictor and Boa imperator. Within the exotic pet trade, it is known as a "BCC"—an abbreviation of its scientific name—to distinguish it from other boa species, such as Boa imperator (known as "BCI" or "boa constrictor imperator"). Other regional names include the chij-chan (Mayan), jiboia (Portuguese), dagwe (Sranan Tongo), and macajuel (Trinidadian). ==Subspecies==

Several subspecies of Boa constrictor have been described in the past, but many of these are poorly differentiated, and further research may redefine many of them. Some appear to be based more on location rather than on biological differences. Boa nebulosa, have all been elevated to full species status. Several other subspecies have been described at different times, but currently, these are no longer considered to be valid subspecies by many herpetologists and taxonomists. They include: • B. c. amarali Stull, 1932 • B. c. melanogaster Langhammer, 1983: a nomen dubium ==Description==

Size and weight The boa constrictor is a large snake, although it is only modestly sized in comparison to other large snakes, such as the reticulated python, Burmese python, or the occasionally sympatric green anaconda, and can reach lengths from depending on the locality and the availability of suitable prey. Clear sexual dimorphism is seen in the species, with females generally being larger in both length and girth than males. The usual size of mature female boas is between whereas males are between . Females commonly exceed , particularly in captivity, where lengths up to or even can be seen. The largest documented non-stretched dry skin is deposited at Zoologische Staatssammlung München (ZSM 4961/2012) and measures without head. A report of a boa constrictor growing up to was later found to be a misidentified green anaconda. The boa constrictor is a heavy-bodied snake, and large specimens can weigh up to . Females, the larger sex, more commonly weigh . Some specimens of this species can reach or possibly exceed , although this is not usual. The size and weight of a boa constrictor depends on subspecies, locale, and the availability of suitable prey. B. c. constrictor reaches, and occasionally tops, the averages given above, as it is one of the relatively large subspecies of Boa constrictor. Pelvic spurs are the only external sign of the rudimentary hind legs and pelvis and are seen in all boas and pythons. Coloring The coloring of boa constrictors can vary greatly depending on the locality. However, they are generally a brown, gray, or cream base color, patterned with brown or reddish-brown "saddles" that become more pronounced towards the tail. This coloring gives B. constrictor subspecies the common name of "red-tailed boas." The coloring works as a very effective camouflage in the jungles and forests of its natural range. Some individuals exhibit pigmentary disorders, such as albinism. Although these individuals are rare in the wild, they are common in captivity, where they are often selectively bred to make a variety of different color "morphs". Boa constrictors have an arrow-shaped head with very distinctive stripes on it: One runs dorsally from the snout to the back of the head; the others run from the snout to the eyes and then from the eyes to the jaw. Boa constrictors also have two lungs, a smaller (non-functional) left and an enlarged (functional) right lung to better fit their elongated shape, unlike many colubrid snakes, which have completely lost the left lung. ==Distribution and habitat==

Depending on the subspecies, Boa constrictor can be found through South America north of 35°S (Colombia, Ecuador, Peru, Venezuela, Trinidad and Tobago, Guyana, Suriname, French Guiana, Brazil, Bolivia, Uruguay, and Argentina), and many other islands along the coasts of South America. Introduced populations exist in Cozumel, extreme southern Florida, and St. Croix in the U.S. Virgin Islands. The type locality given is "Indiis"—a mistake, according to Peters and Orejas-Miranda (1970). B. constrictor flourishes in a wide variety of environmental conditions, from tropical rainforests to arid semidesert country. However, it prefers to live in rainforest due to the humidity and temperature, natural cover from predators, and vast amount of potential prey. It is commonly found in or along rivers and streams, as it is a very capable swimmer. Boa constrictors also occupy the burrows of medium-sized mammals, where they can hide from potential predators. ==Behavior==

Boa constrictors generally live on their own and do not interact with any other snakes unless they want to mate. They are nocturnal, but they may bask during the day when night-time temperatures are too low. As semi-arboreal snakes, young boa constrictors may climb into trees and shrubs to forage; however, they become mostly terrestrial as they become older and heavier. Boa constrictors strike when they perceive a threat. Their bite can be painful, especially from large snakes, but is rarely dangerous to humans. Specimens from Central America are more irascible, hissing loudly and striking repeatedly when disturbed, while those from South America tame down more readily. Domestic animals such as dogs, cats, rabbits, ducks and chickens are frequently consumed. This would lead to unconsciousness and death very quickly. Reproduction and development Boa constrictors are ovoviviparous, giving birth to live young. They generally breed in the dry season—between April and August—and are polygynous; thus, males may mate with multiple females. Half of all females breed in a given year, and a larger percentage of males actively attempt to locate a mate. The Colombian rainbow boa (Epicrates maurus) was found to reproduce by facultative parthenogenesis resulting in production of WW female progeny. The WW females were likely produced by terminal automixis (see Figure), a type of parthenogenesis in which two terminal haploid products of meiosis fuse to form a zygote, which then develops into a daughter progeny. This is only the third genetically confirmed case of consecutive virgin births of viable offspring from a single female within any vertebrate lineage. In 2017, boa constrictors, along with Boa imperators and Burmese pythons, were found to contain a new set of sex determining chromosomes. Males were discovered to contain a pair of XY sex determining chromosomes, while females have a XX pair. During the breeding season, the female boa constrictor emits pheromones from her cloaca to attract males, which may then wrestle to select one to breed with her. After this period, ovulation may not occur immediately, but the female can hold the sperm inside her for up to one year. At this point, they shed less frequently, about every 2–4 months. ==Captivity==

Though still exported from South America in significant numbers, they are widely bred in captivity. Captive life expectancy is 20 to 30 years, with rare accounts of over 40 years. The greatest reliable age recorded for a boa constrictor in captivity is 40 years, 3 months, and 14 days. This boa constrictor was named Popeye and died in the Philadelphia Zoo, Pennsylvania, on April 15, 1977.