Common Northern Boa (S/F)

A small northern boa in the central Isla Nublar forest. Its size indicates that it is either a male, an insular dwarf, or a juvenile. Juveniles tend to be arboreal, while adults favor the forest floor.

The common northern boa (Boa imperator), also called the Central American boa, is a large, heavily-built species of boa snake. It is a member of the family Boidae, which is found throughout Latin America. The common boa is often confused with the red-tailed boa (Boa constrictor constrictor), which is larger, but is found only in South America. Common boas are visually similar, but slightly smaller, and may have less vivid markings; they are found from northern South America through Mexico. This includes offshore islands such as Isla Nublar, where it was the largest terrestrial carnivore until 1989. Its Tun-Si name is currently unknown, but the Bribri word for “snake” is tkabë.

Until fairly recently, Boa imperator was considered a subspecies of Boa constrictor. They are distinguished by having a smaller number of dorsal and anal scales.


The common northern boa ranges in length from three to ten feet, depending on location and diet. It is among the smaller species of boas; the red-tailed boa may exceed ten feet long, while common boas do not. Insular populations of common boas (that is, those found on islands) are often smaller than average.

Color in common boas is variable based on habitat, but they are generally brown, gray, or cream-colored. Brown or reddish-brown saddle patterns run down the length of the body. On the arrow-shaped head, there are a few brown stripes: one running from the snout to the neck, one that bridges the two eyes, and one each that runs from the eye to the jaw. The tail is dark brown or dark red.


Young snakes mostly resemble small versions of the adults, and grow continuously. In the wild they will live for two or three decades, while in captivity they can reach the age of forty.

Sexual Dimorphism

The female generally grows larger and bulkier than the male; females are generally between seven and ten feet long, while males are usually six to eight feet in length. Although the female is larger, the male has a longer tail region than the female due to his reproductive organs. Male boas have pelvic spurs, which are the remnants of legs, that they use to grip females to mate.

Preferred Habitat

Northern boas live on the edges of forested areas. Their bodies help to camouflage them in this environment, allowing them to escape predators and sneak up on prey. As a good swimmer, it can be found near sources of fresh water. However, it can adapt to semi-arid regions, even though it prefers rainforest. Younger snakes tend to live in trees, while the older individuals become too heavy and are mostly restricted to the ground.

Natural range

This animal lives in Central America. The northern end of its native range is in eastern Mexico, favoring the Caribbean coast; it also can be found in most of southern Mexico including the entire Yucatán Peninsula. In the south, it lives on both the Atlantic and Pacific sides of northern Colombia, and in parts of coastal Ecuador. Some boas (often insular dwarf forms) can be found on offshore islands, such as Isla Nublar in the Gulf of Fernandez. Located about 120 miles off the Pacific coast of Costa Rica, this island is fairly remote but nonetheless historically had a common boa population. The construction of Jurassic Park between 1988 and 1993, the presence of de-extinct species in the wild between 1993 and 2002, and then the construction and operation of Jurassic World between 2002 and 2015 harmed their habitat; de-extinct animals were again released into the wild after 2015, but were mostly killed off by the eruption of Mount Sibo in 2018. During the eruption, much of the island’s forested habitat was destroyed; it is unknown if any boas survived after this point.

This snake may also live on other islands in the Gulf of Fernandez. Large snakes have been reported from Isla Sorna, the largest island in the Muertes Archipelago, but the species has not been identified; Latin America has other large snake species such as the bushmaster (genus Lachesis), which can get to similar sizes.


Common boas are frequently a part of the pet trade around the world. They are often erroneously called the Colombian red-tailed boa constrictor (this correctly refers to Boa constrictor, which is found farther south). Zoos are more likely to label it correctly so long as their signage is up to date. While it cannot survive long in cold climates, it has been reported having escaped into the wild from less skilled animal owners; others may release it intentionally after not researching how large it grows. Escaped or released animals have been found mainly in the United States, where the exotic pet trade is prominent and irresponsible pet ownership is widespread, but this can happen anywhere. Due to concerns about the species becoming invasive should it be released somewhere it can survive, authorities usually are sent to capture the reptiles and place them in the care of a trusted organization or person.

Behavior and Ecology
Activity Patterns

Boas are crepuscular. They mainly hunt at night, but come out during the day to bask in the sun. Diurnal activity is more common when nighttime temperatures are low; since the boa is ectothermic, it must warm up in order to hunt.

Diet and Feeding Behavior

Common boas are predators of small to medium-sized animals as adults, mostly mammals and birds. Younger boas feed on amphibians, reptiles, and other small creatures. They are generally nocturnal, but often come out during the day to bask in the sun. These are ambush predators and excel at camouflage. Killing by constriction, the boa holds its prey with its teeth while squeezing with its body to cut off blood flow to the brain. Once its prey is unconscious or dead, the boa swallows it whole, digesting it over the course of four to six days. The snake’s metabolism is so slow that it may not eat for weeks or months afterward.

The most numerous endemic species on Isla Nublar, the Nublar tufted deer, is a likely prey item for the common boa. It may have preyed on other small animals including smaller birds, brown rats, fish, feral goats, and small dinosaurs such as Compsognathus and Microceratus.

Social Behavior

These snakes are solitary except when mating.


Common northern boas mate in polygynous groups; that is, a male will mate with several females. Usually, about half of the females will breed in a given year. Mating takes place during the dry season, typically from April to August. Females emit a scent to attract males, who wrestle for mating rights. After mating, a female may not become pregnant immediately; there may be a delay of up to a year.

Once she ovulates, a female sheds her skin and begins the gestation period. This will last for between 100 and 120 days. She will give birth to live young, with broods numbering between ten and sixty-five with an average of twenty-five. There is a good chance that several of the young will be stillborn, or even unfertilized eggs. No parental care is provided.


Most snakes are very quiet, and the common boa is not an exception. It may hiss if threatened in order to try and frighten away predators. Communication between animals is mostly conveyed by body language and pheromones.

Ecological Interactions

When young, the common boa is semi-arboreal and often climbs into trees or shrubs. Its forest habitat has shaped its evolution, and its camouflaged coloration is meant to hide it among foliage. As an adult it lives on the forest floor, hiding in leaf litter. Among the largest constrictor snakes, it begins its life feeding on rodents, frogs, lizards, and birds, taking larger prey as it gets older.

On Isla Nublar, the common boa was the largest terrestrial carnivore confirmed on the island. This would mean that before InGen, it had few (if any) predators as an adult. It was likely a predator of the Nublar tufted deer, a species endemic to the island. While common boas are not likely fast or strong enough to be a threat to many adult dinosaurs, some smaller dinosaurs and juveniles could possibly be threatened by a boa. Its camouflaged body coloration would help the boa evade predatory dinosaurs, making it possible for it to survive after dinosaurs were introduced to its habitat.

In 1993, a small common boa encountered an adult female Velociraptor antirrhopus nublarensis, but showed no signs of fear. This may be due to the fact that there were no large carnivorous animals on Isla Nublar prior to 1989, when predatory dinosaurs were first introduced. However, the raptor did not pay the snake any attention, and both animals presumably left one another alone.

As with all animals found in the wild it can suffer from parasites. Common boas are known to have both endoparasites and ectoparasites. A common pest is the reptile mite Ophionyssus natricis, which feeds on its blood and can cause skin irritation.

Cultural Significance

The power of the boas as predatory animals has long captivated the human species and depictions of boas are common in artwork from Latin America dating back throughout history. Its skin patterns, while evolved for camouflage, are considered beautiful by many people. Snakes are less favorably seen in European cultures, where they are used as symbols of treachery or deceit; this is especially common in regions where Christianity is the dominant religion. The negative perception of snakes is linked to venomous species, and large constrictors are uncommon in Europe, so the boas are often lumped in with the venomous snakes of the Mediterranean or even mistaken for venomous species themselves.

During the colonial era in the Americas, the boas were discovered by Europeans to much surprise, fascination, and fear. While these were common species well-known by local people, they were unfamiliar to many Europeans, whose only knowledge of large constrictors would have come from the pythons of Africa and the Middle East. Boas and other large constrictors became symbols of the exotic; even today, large constrictor snakes are linked to exoticism and foreign lands in the cultures of countries such as the United States.

In Captivity

The common boa is frequently found in the international pet trade, though it is often mistaken for (and marketed as) its close relatives such as the red-tailed boa. The scientific name “Boa constrictor” is used incorrectly in the reptile trade to describe the common boa as well as the actual boa constrictor.

It is a relatively docile snake, making it easy to handle and thus favorable with reptile-keepers. The wide variety of color patterns they can be bred for also increase their appeal. If kept healthy, it can attain quite a large size, which necessitates a larger enclosure to house it. Younger snakes will climb if given the chance, so their enclosures often include branches, logs, and other wooden structures to make the environment more dynamic. This has the added benefit of mimicking the animal’s natural habitat, which can help it remain more comfortable in captivity.

As with all ectothermic species, it needs to be kept warm, but it can acclimate to humid or semi-arid conditions.

This reptile feeds on small animals in the wild which it hunts by ambush, but in captivity it can be raised on pre-killed food items. It is often fed dead rats. Some keepers choose to give it live food, but this is not recommended by experts; preying on a live animal involves a struggle, during which the prey may injure the predator in an attempt to escape. To keep your snake safe, it is best to give it prepared food. Bear in mind that it has a slow metabolism, needing to feed periodically with somewhat long gaps in between meals; it takes days to digest its prey.

Especially in animals caught from the wild, the common boa can be affected by various parasites, such as reptile mites. Fortunately, there are commercially-available medical treatments, ranging from antibiotics to predatory mites which eat the pests. Insecticides are harmful to snakes, though they can be used to treat an infected habitat; only do this after safely removing the snake, and reintroduce it only once the insecticide is no longer present.

Like all snakes, it sheds its skin as it grows and will be vulnerable during this process. As the skin over its eyes is shed, it will have a hard time seeing, and may require help finding food. Take care not to startle it during the shed cycle; it will be more defensive as its vision is impaired.


Since they are large and easily obtained, common northern boas are sometimes used for snake research. For example, it was discovered in 2017 that they are one of only two known species of snakes to use the XY sex chromosome system; most reptiles use other systems. They are also a notable example of regional variation within a species (though they have not yet been classified into subspecies as of this writing): scientists have documented populations in locations such as Nicaragua and the Cayos Cochinos which are distinctly different from one another. The common boa itself was once considered a subspecies of Boa constrictor, but it was discovered in 2018 that it actually differs from this species in five to seven percent of its genome.


This species is ranked at Least Concern by the International Union for Conservation of Nature, meaning it is not in immediate danger of extinction. The main threat to its survival is habitat loss, chiefly deforestation. Fortunately, it is able to acclimate to semi-arid regions and some deserts.


While historically it would be killed for its skin, used to make leather for fashionable clothing and accessories, the common boa is now more often used as a pet. Between 1989 and 2000, the Global Invasive Species Database reported 115,131 common northern boas imported into the animal trade. They have the potential to become invasive, especially in wetland areas such as the American Southeast where they readily acclimate to the new habitat.

Snake breeders often choose this species for the variety of pigmentation it can exhibit. The common boa already naturally has several different color patterns available, and breeding them for certain patterns is fairly easy. These include melanistic and mottled patterns, in addition to some which are rare in nature, such as albinos.


While the common boa is a fairly docile snake, individuals found in Nicaragua are generally more irritable than those in South America and are more likely to bite if approached. Usually they will hiss as a warning first; even the less aggressive varieties will put on a threat display first, but the Nicaraguan boas are the only ones likely to bite repeatedly until you back down. Larger snakes can give more painful bites, but they are usually not extremely dangerous to humans; back away from the snake as quickly as you can, and get the bites inspected by a medical professional. Boas do not prey on humans and so will only attack defensively. Be careful walking through their forest habitat, since they remain hidden with their camouflaged patterns, and do not provoke one if you encounter it. Simply walk around and do not linger next to a wild snake; show that you are not a threat and it will conserve its energy by ignoring you.

In the extremely rare occasion that a common boa attempts to constrict you, which most often happens after mishandling the animal, have another person grab it by the tail and unwind it from your body. Hold it just behind the head to maintain control and prevent it from biting you. Be gentle when holding captive specimens, and acclimate them to contact if you intend to hold one often. They can become very docile as pets, but getting them accustomed to you must come first. Be especially careful if you have small children or other pets around.

Also keep in mind that shedding is a perilous time for the snake. While it is shedding, its vision will be impaired and its fresh skin will be highly sensitive. This will make it vulnerable and nervous, so it will be more likely to give a defensive bite if it is frightened. Be especially gentle with shedding snakes and do not surprise them.