Interesting Creatures… The Boa Constrictor

Dec 09, 2018 Features / Columnists, Interesting Creatures in Guyana

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The Boa constrictor, also called the red-tailed boa or the common boa, is a species of large, non-venomous, heavy-bodied snake that is frequently kept and bred in captivity.
The boa constrictor is a member of the family Boidae, found in tropical North, Central, and South America, as well as some islands in the Caribbean.
A staple of private collections and public displays, its colour pattern is highly variable yet distinctive. Ten subspecies are currently recognized, although some of these are controversial. This article focuses on the species Boa constrictor as a whole, and on the nominate subspecies B. c. constrictor.
Though all boids are constrictors, only this species is properly referred to as a “boa constrictor” – a rare instance of an animal having the same common English name and scientific binomial name.
The boa constrictor can reach lengths from 3–13 ft (0.91–3.96 m) 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 7 and 10 ft (2.1 and 3.0 m) whereas males are 6 and 8 ft (1.8 and 2.4 m). Females commonly exceed 10 ft (3.0 m), particularly in captivity, where lengths up to 12 ft (3.7 m) or even 14 ft (4.3 m) can be seen.
This reptile is a heavy-bodied snake, and large specimens can weigh up to 27 kg (60 lb). Females more commonly weigh 10 to 15 kg (22 to 33 lb). Some specimens of this species can reach or possibly exceed 45 kg (100 lb), 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.
Other examples of sexual dimorphism in the species include males generally having longer tails to contain the hemipenes and also longer pelvic spurs, which are used to grip and stimulate the female during copulation. Pelvic spurs are the only external sign of the rudimentary hind legs and pelvis, seen in all boas and pythons.
The colouring of boa constrictors can vary greatly depending on the locality. However, they are generally a brown, grey, or cream base colour, patterned with brown or reddish-brown “saddles” that become more pronounced towards the tail. The colouring works as very effective camouflage in the jungles and forests of its natural range.
Also, 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 colour “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 can sense heat via cells in their lips, though they lack the labial pits surrounding these receptors seen in many members of the family Boidae. They have two lungs, a smaller (nonfunctional) left and an enlarged (functional) right lung to better fit their elongated shape, unlike many colubrid snakes, which have completely lost the left lung.
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.
Like all snakes, boa constrictors in a shed cycle are more unpredictable, because the substance that lubricates between the old skin and the new makes their eyes appear milky, blue, or opaque, so that the snake cannot see very well, causing it to be more defensive than it might be otherwise.
Prey includes a wide variety of small to medium-sized mammals and birds. The bulk of their diet consists of rodents, but larger lizards and mammals as big as ocelots are also reported to have been consumed. Young boa constrictors eat small mice, birds, bats, lizards, and amphibians. The size of the prey item increases as they get older and larger.
Boa constrictors are ambush predators, so often lie in wait for an appropriate prey to come along, when they attack. However, they have also been known to actively hunt, particularly in regions with a low concentration of suitable prey, and this behaviour generally occurs at night.
The boa first strikes at the prey, grabbing it with its teeth; it then proceeds to constrict the prey until death before consuming it whole. Unconsciousness and death likely result from shutting off vital blood flow to the heart and brain, rather than suffocation as was previously believed; constriction can interfere with blood flow and overwhelm the prey’s usual blood pressure and circulation. This would lead to unconsciousness and death very quickly. Their teeth also help force the animal down the throat while muscles then move it toward the stomach.
It takes the snake about 4–6 days to fully digest the food, depending on the size of the prey and the local temperature. After this, the snake may not eat for a week to several months, due to its slow metabolism [Source – Wikipedia]

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