Alsophis portoricensis (Puerto Rican Racer)

Alsophis portoricensis (Puerto Rican Racer)


Snakes belong to a very interesting group of animals known as reptiles. Reptiles are animals that have an external protective layer of epidermal scales. These scales are quite thick, dry, bright, and protect reptiles from drying out; that is why they can live away from water. Amphibians (frogs, for example) do not have this protective layer and need to live in or near water or in very humid environments. Reptiles can lay their eggs on the ground or, in some cases, are viviparous -which means that they do not lay eggs but rather give birth to live offspring.

Snakes are unique among reptiles because they have no members or external ear openings, and they do not have eyelids. Although they lack these characteristics, they are very successful animals and can live in a variety of environments.

Snakes of Puerto Rico

Islands tend to have fewer species of animals than regions on the continent that have the same climate and latitude, mainly because of the large areas of water that isolate them. Puerto Rico is no exception and only has four species of snakes. These four snakes, however, are found in most of the island, and each one is quite distinctive and easily identified.

Blind snakes (Typhlops)

These are the smallest snakes in Puerto Rico and do not measure more than 30 centimeters long. They are characterized by a blunt head, rudimentary eyes, (they look like a dark stain under the scales), very small scales in the belly, and a special scale in the shape of an acute cone on the tip of the tail. They are usually light brown to brown or gray. They are found throughout the island; these snakes are of cryptic habits and spend most of the time underground. Many times they are found inside termite nests, under and inside rotting tree trunks, and under piles of trash. They feed on ants, termites, and other small insects and can be found outside after a downpour. This snake does not bite when touched (it has no teeth) but squirms and has the habit of pushing its tail against the manipulator’s skin. In no way, however, does this action cause a bite. Blind snakes lay eggs.

Puerto Rican Boa (Epicrates)

This is the largest snake in Puerto Rico and belongs to the family of Boidae snakes, which include the largest snakes in the world. The snake can reach a length of more than two meters and is generally dark brown. Many times it seems to reflect colors and appears to be iridescent. This snake has been seen in many parts of Puerto Rico, but appears to be more common in mountainous and rocky places where it can find deep openings and cracks where it can hide. If such places are not available, it can take refuge in abandoned buildings or huge piles of garbage. The snake eats rats, mice, birds, bats, and probably sometimes chickens. It is only active after dusk, and that is when it is usually found. Although it is not poisonous, the Puerto Rican Boa defends itself by biting and can inflict a pretty serious wound because of its large and sharp teeth. However, when touched smoothly, it is likely that it will not bite. This species is the only snake in Puerto Rico to give birth to live offspring. Their numbers have declined due to the increasing human population and housing construction. Because of this, it is an endangered species and there are fines for collecting or hurting them.

Garden snake (Arrhyton)

This small but common snake in Puerto Rico reaches a length of 45 centimeters and is distinguished by having a brown background and two dark lateral lines. In addition, when carefully looking at the back of each scale, we see that there is only one small pore or none. It is generally a very active snake during the day, but because of its secretive habits is seen very rarely. It feeds mostly lizards and is found in dry grass and leaves in wooded regions, under rotting tree trunks, in abandoned buildings, and in heaps of garbage. This snake lays eggs and, like the Epicrates, its numbers have declined recently.

Puerto Rican Racer (Alsophis)

It is the second largest snake in Puerto Rico (more than one meter in length) and is often confused with Arrhyton. It usually has a uniform color, light to dark brown (sometimes almost black), and has a white belly. There are no lateral lines, but some white stains are seen on the sides of some animals. The eyes are relatively larger than those of Arrhyton; and when carefully examining the back of each dorsal scale there are usually two or three small pores. Alsophis is found almost all over the island and in some regions may be quite abundant. It feeds on lizards, frogs, and other snakes. Its saliva is poisonous and a prolonged bite can cause inflammation or worse complications. This snake is often very aggressive and sometimes expands the skin of the neck like a cobra and repeatedly attacks the intruder. It is very abundant in mountain areas where there are many openings and cracks where it can hide. It is very active during the day but can be found moving at dusk. In addition to being found among rocks, grasses, and leaves, Alsophis is seen in trees where it easily moves from one branch to another. It lays eggs.

Determining its gender

One of the most common questions about snakes is “How can we tell the difference between males and females?” It is usually very difficult to determine their gender simply by observing the specimen. However, their gender may be verified using the following procedure: Males have a double copulative organ, and each is called a hemipenis. Each hemipenis is located in the tail following the cloacal opening, one on the right side and one on the left side. During copulation, a hemipenis (right or left) turns inside out from its receptacle in the tail. The female has no such organ. Using a blunt probe can determine the sex of any snake. The probe is introduced gently from the right or left side of the cloacal opening. If it does not go into a deep sack, the animal is female. If it goes into a deep sack, it is male.


Snakes, unfortunately, have a bad reputation and all over the world there are stories about how evil this animal is. Most of the stories, however, are not true. Often they originate from ignorance; people do not understand that snakes are highly specialized reptiles and do not possess magical powers. With understanding, we can realize that these animals are not terrible.

The following is a list of superstitions —things that are believed but are not really true—:
• Snakes are moist and viscous (The truth is that their skin is drier than that of humans).
• Snakes can stare at people and animals and enchant them. (They only seem to stare because they have no eyelids and cannot blink).
• The oil and other organs of the snake’s body possess magical healing powers (There is no documentation to support this).
• Snakes can suck milk from cows or a woman’s chest. (Snakes can be found in barns and houses, but they are looking for rats and mice, which are found there. They are not sucking milk).
• If a chicken eats a blind snake (Typhlops) and then someone eats that chicken, this person will die. (Absolutely false).
• “Snakes can hold their tail with their mouth and turn like a wheel. (Absolutely false).


Puerto Rico has the good fortune of having representatives of four kinds of snakes. It is also fortunate that none of them is dangerous to humans. On the contrary, the majority provides a tremendous service by feeding on insects and pests such as rats and mice.

By: James C. Gillingham
Prepared by: Cuerpo de investigadores científicos auxiliaries
(Assistant Research Scientists)

Author: Grupo Editorial EPRL
Published: August 27, 2014.

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