Boa constrictors are predators on birds and small mammals, including bats. They are important predators of rodents and opossums, especially, which can become pests in some areas and carry human diseases.
When threatened, boa constrictors will bite to defend themselves. Though there are few references to predation on boa constrictors in nature, they are certainly killed and consumed by numerous reptilian, avian, and mammalian predators. Young boas are especially vulnerable.
Anti-predator Adaptations: cryptic
Boa constrictor has long been famous as one of the largest species of snake. In reality, boa constrictors are fairly modest-sized boids and are dwarfed by the other competitors for this title. The maximum length reported in B. constrictor was slightly over 4 meters. Individuals are generally between 2 and 3 meters in length, although island forms are commonly below 2 meters. Within populations, females are usually larger than males. However, the tails of males may be proportionally longer than those of females because of the space taken up by the hemipenes. Boa constrictor coloration and pattern are distinctive. Dorsally the background color is cream or brown that is marked with dark "saddle-shaped" bands. These saddles become more colorful and prominent towards the tail, often becoming reddish brown with either black or cream edging. Along the sides, there are rhomboid, dark marks. They may have smaller dark spots over the entire body. The head of a boa constrictor has 3 distinctive stripes. First is a line that runs dorsally from the snout to the back of the head. Second, there is a dark triangle between the snout and the eye. Third, this dark triangle is continued behind the eye, where it slants downward towards the jaw. However, there are many variations on appearance. At least 9 subspecies are currently recognized by some authorities, although many of these are poorly defined and future research will undoubtedly modify this taxonomy. Currently acknowledged subspecies include: B. c. constrictor, B. c. orophias, B. c. imperator, B. c. occidentalis, B. c. ortonii, B. c. sabogae, B. c. amarali, B. c. nebulosa (Dominican boa, recently elevated to full species), and B. c. longicauda. Most of these subspecies are distinguished largely by their range rather than appearance, but regional (subspecific) variation in form, size, and coloration does occur.
As in most members of the family Boidae, boa constrictors possesses pelvic spurs. These are hind leg remnants found on either side of the cloacal opening. They are used by males in courtship and are larger in males than in females. Males possess hemipenes, a double-penis, of which only one side is commonly used in mating. Although heat-sensing pits are common in Boidae, they are absent in B. constrictor. Thus, this species is presumed to have no specialized thermosensory abilities. The teeth of boa constrictors are aglyphous, meaning they do not possess any elongated fangs. Instead, they have rows of long, recurved teeth of about the same size. Teeth are continuously replaced; particular teeth being replaced at any one time alternate, so that a snake never loses the ability to bite in any part of its mouth. Boas are non-venomous. Boa constrictors have two functional lungs, a condition found in boas and pythons. Most snakes have a reduced left lung and an extended right lung, to better match their elongated body shape.
Range length: 1 to 4 m.
Average length: 2-3 m.
Other Physical Features: heterothermic ; polymorphic
Sexual Dimorphism: female larger
Boa constrictors are potentially long-lived, perhaps averaging around 20 years old. Captive boas tend to live longer than wild ones, sometimes by as much as 10 to 15 years.
Range lifespan
Status: wild: 30 (high) years.
Range lifespan
Status: captivity: 40 (high) years.
Average lifespan
Status: wild: 20 years.
Typical lifespan
Status: captivity: 25 to 35 years.
Boa constrictors occupy a variety of habitats. Primary habitat is rainforest clearings or edges. However, they are also found in woodlands, grasslands, dry tropical forest, thorn scrub, and semi-desert. Boa constrictors are also common near human settlements and often found in agricultural areas. Boa constrictors are commonly seen in or along streams and rivers in appropriate habitats. Boa constrictors are semi-arboreal, although juveniles tend to be more arboreal than adults. They also move well on the ground and can be found occupying the burrows of medium-sized mammals.
Range elevation: 0 to 1,000 m.
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: savanna or grassland ; chaparral ; forest ; rainforest ; scrub forest
Aquatic Biomes: rivers and streams
Other Habitat Features: agricultural ; riparian
Boa constrictor is an exclusively New World species which has the largest distribution of all neotropical boas. Boa constrictors range from northern Mexico south through Central and South America. In South America the range splits along the Andes mountains. To the east of the Andes, B. constrictor is found as far south as northern Argentina. On the west side of the mountains, the range extends into Peru. Boa constrictors are also found on numerous islands off the Pacific coast and in the Caribbean. Islands included in the boa constrictor range are: the Lesser Antilles, Trinidad, Tobago, Dominica, and St. Lucia. Some islands off the coast of Belize and Honduras are also inhabited by this species.
Biogeographic Regions: nearctic (Native ); neotropical (Native )
Boa constrictors are carnivorous generalists. The main bulk of their diet consists of small mammals, including bats, and birds. However, they will eat any animal they can capture and fit in their mouths. Boa constrictors capture prey through ambush hunting, although occasionally they actively hunt. They can rapidly strike at an animal that passes by a branch that they are suspended from, for example. They are non-venomous and prey is dispatched through constriction. Boa constrictors wrap their prey in the coils of their body and squeeze until the prey asphyxiates. This is especially effective against mammals and birds whose warm-blooded metabolism demands oxygen at a rapid rate. Once dead, the prey is swallowed whole. Interestingly, if captive boa constrictors are presented with dead prey, they still constrict the food item before consuming it. It takes boa constrictors 4 to 6 days to fully digest a meal.
Animal Foods: birds; mammals; amphibians; reptiles; eggs
Primary Diet: carnivore (Eats terrestrial vertebrates)
Boa constrictors are popular in the pet trade. It is easy to obtain boa constrictors that have been captive bred for generations, increasing their affinity for humans. They are relatively undemanding pets, as long as their large adult size and space needs are accounted for. Proper levels of heat and humidity (boas usually need a dry climate, otherwise their scales will develop rot) need to be observed. Boa constrictors can be fed dead mice and rats and only require food and defecate about once a week. Proper care should be observed in handling them, especially the larger varieties. Boa constrictors, whole or in parts, are also seen in local markets within their range, presumably as food or medicine. They are sometimes harvested for the skin trade. In some areas boas constrictors can play a large role in controlling populations of pest rodents and opossums (Didelphidae). Opossums in the tropics can be carriers for the human disease leishmaniasis, which is transferred by blood-feeding sand flies (Psychodidae) that parasitize the opossums. Boa constrictor predation pressure may help to regulate opossum populations and decrease potential trasmission of leishmaniasis to humans.
Positive Impacts: pet trade ; food ; body parts are source of valuable material; controls pest population
Little negative impact on humans is known. Boa constrictors rarely, if ever, attack humans except in self-defense. Humans, even children, are far outside the range of prey size taken by boas. Boa constrictor bites are painful bure are unlikely to be dangerous as long as standard medical care is obtained. Boa constrictors are not venomous. Large captive snakes must always be handled with extreme care, especially when being fed, as a hungry snake strikes and constricts in a largely automatic sequence of behaviors. Very large snakes should handled and fed only with more than one person present.
Negative Impacts: injures humans (bites or stings)
Fertilization is internal, with mating facilitated by the pelvic spurs of males. Boa constrictors are ovoviviparous; embryos develop within their mothers' bodies. Young are born live and are independent soon after birth. Newborn boa constrictors resemble their parents and do not undergo any metamorphosis. As in other snakes, boa constrictors shed their skins periodically as they age, allowing them to grow and preventing the scales from becoming worn. As a boa grows, and its skin is shed, its coloration may gradually change. Young snakes tend to have brighter colors and more contrast between colors, but most changes are subtle.
Overcollection for the pet trade and needless direct persecution has had an impact on some B. constrictor populations. Some populations have been hit harder than other, and various wild populations are now endangered, particularly those on offshore islands. On the mainland, boa constrictors have been harvested for their skins, meat and body parts. Furthermore, habitat loss and road mortality has reduced populations. Most boa constrictors are on the CITES Appendix 2 list. The subspecies B. c. occidentalis is on Appendix 1 of CITES.
US Federal List: no special status
CITES: appendix i; appendix ii
State of Michigan List: no special status
Like most snakes, boa constrictors rely on strong vomeronasal senses. Their tongues flick continuously, bringing odor molecules into contact with the chemosensory (vomeronasal) organ in the top of their mouths. In this manner, they constantly sense chemical cues in their enviornment. Boa constrictors have good vision, even into the ultraviolet spectrum. In addition, they can detect both vibrations in the ground and sound vibrations through the air through their jaw bones. They do not have external ears. Unlike most boids, boa constrictors lack thermosensory pits.
Communication Channels: tactile ; chemical
Perception Channels: visual ; tactile ; acoustic ; vibrations ; chemical
As mentioned above, the species Boa constrictor is divided into many subspecies. These subspecies are highly variable and over the years the taxonomy has changed. Currently there are at least 9 recognized subspecies: Colombian or common boa constrictors (B. c. constrictor), St. Lucia boa constrictors (B. c. orophias), Imperial or Central American boa constrictors (B.c. imperator), Argentine boa constrictors (B.c. occidentalis), Peruvian boa constrictors (B.c. ortonii), Taboga Island boa constrictors (B.c. sabogae), Bolivian boa constrictors (B.c. amavali), Dominican or clouded boa constrictors (sometimes considered a full species, B.c. nebulosa), and long-tailed boa constrictors (B.c. longicauda). Subspecies that are occasionally cited, but are not as widely acknowledged or are often combined with a previously listed subspecies are: Mexican boa constrictors (B.c. mexicana), black-bellied boa constrictors (B.c. melanogaster), and Tres Marias Islands boa constrictors (B.c. sigma). As apparent by the names, most subspecies are recognized by their range. In many cases, a boa constrictor of unknown geographical origin may be impossible to assign to a subspecies. Additionally, pet trade breeders have created many new color morphs that are not seen in wild populations.
Males are polygynous; each male can mate with multiple females. Females may also have more than one mate in a season. Females are usually widely scattered and courting males must invest energy into locating them. Most female boa constrictors do not appear to reproduce annually. Usually about half of the female population is reproductive each year. Furthermore, females likely become reproductive only when they are in good physical condition. While a higher percentage of males seems to reproduce each year, it is likely that the majority of males also do not reproduce annually.
Mating System: polygynandrous (promiscuous)
Boa constrictors generally breed during the dry season, usually from April to August, though the timing of the dry season varies across their range. Gestation lasts for 5 to 8 months depending on local temperatures. The average litter has 25 young but can be anywhere from 10 to 64 young.
Breeding interval: Females perhaps every other year, or less often, depending on condition.
Breeding season: Breeding occurs during the dry season (April-August), birth occurs 5-8 months later.
Range number of offspring: 10 to 64.
Average number of offspring: 24 (in <>).
Range gestation period: 5 to 8 months.
Average time to independence: after only a few minutes.
Average age at sexual or reproductive maturity (female): 2-3 years.
Average age at sexual or reproductive maturity (male): 2-3 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; sexual ; fertilization ; viviparous
Maternal investment in young is considerable and requires the mother to be in good physical condition. Since young boa constrictors develop within the mother's body, they are able to develop in a thermoregulated, protected environment and they are provided with nutrients. Boa constrictor young are born fully developed and are independent within minutes of birth. Male reproductive investment is largely spent in finding mates.
Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female)
The boa constrictor (scientific name also Boa constrictor), also known as the red-tailed boa, is a species of large, non-venomous, heavy-bodied snake that is frequently kept and bred in captivity.[5][6] The boa constrictor is a member of the family Boidae. The species is native to tropical South America. A staple of private collections and public displays, its color pattern is highly variable yet distinctive. Four subspecies are recognized.[7] 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 the "boa constrictor" — an instance of an animal having the same English common name and scientific binomial. Only one other vertebrate animal shares this trait, the theropod dinosaur Tyrannosaurus rex.
All subspecies are referred to as "boa constrictors", and are part of a diverse group of New World boas referred to as "red-tailed" boas, comprising the species Boa constrictor and Boa imperator. Within the exotic pet trade, it is also known as a "BCC", an abbreviation of its scientific name, to distinguish it from other boa species, such as Boa imperator or "BCI."
Other common names include chij-chan (Mayan),[8] jiboia (Latin American), and macajuel (Trinidadian).[9]
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.[10] Boa imperator,[11] Boa nebulosa,[3] Boa orophias and Boa sigma[12] 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.[15] They include:
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 3 to 13 ft (0.91 to 3.96 m) depending on the locality and the availability of suitable prey.[16] 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 between 6 and 8 ft (1.8 and 2.4 m).[17] 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.[18] The largest documented non-stretched dry skin is deposited at Zoologische Staatssammlung München (ZSM 4961/2012) and measures 14.6 ft (4.45 m) without head.[19] A report of a boa constrictor growing up to 18.5 ft (5.6 m) was later found to be a misidentified green anaconda.[20]
The boa constrictor is a heavy-bodied snake, and large specimens can weigh up to 27 kg (60 lb). Females, the larger sex, more commonly weigh 10 to 15 kg (22 to 33 lb).[21] Some specimens of this species can reach or possibly exceed 45 kg (100 lb), although this is not usual.[22]
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.[17]
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.[23] Pelvic spurs are the only external sign of the rudimentary hind legs and pelvis and are seen in all boas and pythons.
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.[17]
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.[24] 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.
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, [25] extreme southern Florida,[26] and St. Croix in the U.S. Virgin Islands.[27] The type locality given is "Indiis"—a mistake, according to Peters and Orejas-Miranda (1970).[4]
B. constrictor flourishes in a wide variety of environmental conditions, from tropical rainforests to arid semidesert country.[28] 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.[17]
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.[29] 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.[28] 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 otherwise be.
Their prey includes a wide variety of small to medium-sized mammals and birds.[29] The bulk of their diet consists of rodents (such as squirrels, mice, rats and agoutis), but larger lizards (such as ameivas, iguanas and tegus) and mammals as big as monkeys, marsupials, wild pigs and ocelots are also reported to have been consumed.[28][30][31] 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 they often lie in wait for an appropriate prey to come along, then they attack a moment before the prey can escape. However, they have also been known to actively hunt, particularly in regions with a low concentration of suitable prey, and this behavior 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.[32] This would lead to unconsciousness and death very quickly.[32] 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.[33]
Boa constrictors are viviparous, giving birth to live young.[34] They generally breed in the dry season—between April and August—and are polygynous; thus, males may mate with multiple females.[35] Half of all females breed in a given year, and a larger percentage of males actively attempt to locate a mate.[35] Due to their polygynous nature, many of these males will be unsuccessful. As such, female boas in inadequate physical condition are unlikely to attempt to mate, or to produce viable young if they do mate.[35] Reproduction in boas is almost exclusively sexual. In 2010, a boa constrictor was shown to have reproduced asexually via parthenogenesis.[36] The Colombian rainbow boa (Epicrates maurus) was found to reproduce by facultative parthenogenesis resulting in production of WW female progeny.[37] 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.[38] Males were discovered to contain a pair of XY sex determining chromosomes, while females have a XX pair.[38] This is the first time snakes were thought to contain male heterogamety, and since then has been found in ball pythons (Python regius) as well.[39]
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.[24] During breeding, the male curls his tail around the female's and the hemipenes (or male reproductive organs) are inserted. Copulation can last from a few minutes to several hours and may occur several times over a period of a few weeks.[40] After this period, ovulation may not occur immediately, but the female can hold the sperm inside her for up to one year.[40] When the female ovulates, a midbody swell can be noticed that appears similar to the snake having eaten a large meal.[40] The female then sheds two to three weeks after ovulation, in what is known as a post-ovulation shed which lasts another 2–3 weeks, which is longer than a normal shed.[40] The gestation period, which is counted from the postovulation shed, is around 100–120 days.[40] The female then gives birth to young that average 15–20 in (38–51 cm) in length.[29] The litter size varies between females but can be between 10 and 65 young, with an average of 25, although some of the young may be stillborn or unfertilized eggs known as "slugs". The young are independent at birth and grow rapidly for the first few years, shedding regularly (once every one to two months). At 3–4 years, boa constrictors become sexually mature and reach the adult size of 6–10 feet (1.8–3.0 m), although they continue to grow at a slow rate for the rest of their lives.[10] At this point, they shed less frequently, about every 2–4 months.[41]
This species does well in captivity, usually becoming quite tame. It is a common sight in both zoos and private reptile collections. Though still exported from their native South America in significant numbers, they are widely bred in captivity. When kept in captivity, they are fed mice, rats, rabbits, chickens, and chicks depending on the size and age of the individual. Captive life expectancy is 20 to 30 years, with rare accounts of over 40 years,[42] making them a long-term commitment as a pet. 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.[43] Proper animal husbandry is the most significant factor in captive lifespan; this includes providing adequate space, correct temperatures and humidity, and suitable food items.[41]
Up to 41.5% of captive boas test positive for eosinophilic inclusion bodies.[44]
Boa constrictors are very popular within the exotic pet trade and have been both captured in the wild and bred in captivity. Today, most captive boa constrictors are captive-bred, but between 1977 and 1983, 113,000 live boa constrictors were imported into the United States.[10] These huge numbers of wild-caught snakes have put considerable pressure on some wild populations. Boa constrictors have also been hunted for their meat and skins, and are a common sight at markets within their geographic range. After the reticulated python, boa constrictors are the snake most commonly killed for snakeskin products, such as shoes, bags, and other items of clothing.[10] In some areas, they have an important role in regulating the opossum populations, preventing the potential transmission of leishmaniasis to humans.[45] In other areas, they are often let loose within the communities to control the rodent populations.
All boa constrictors fall under CITES and are listed under CITES Appendix II, except B. c. occidentalis, which is listed in CITES Appendix I.[46]
In some regions, boa constrictor numbers have been severely hit by predation from humans and other animals and over-collection for the exotic pet and snakeskin trades. Most populations, though, are not under threat of immediate extinction; thus, they are within Appendix II rather than Appendix I.[46]
Boa constrictors may be an invasive species in Florida and Aruba.[47]
The boa constrictor (scientific name also Boa constrictor), also known as the red-tailed 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. The species is native to tropical South America. A staple of private collections and public displays, its color pattern is highly variable yet distinctive. Four subspecies are recognized. This article focuses on the species Boa constrictor as a whole, and on the nominate subspecies B. c. constrictor.
