Cat Snake

The term cat snake is used to refer to snakes that belong to the family Colubridae. The term is defined as an umbrella term that is used to define various members or various species of the snakes that are classified under this family. Now the question arises about the etymology of the term, cat snake as the name suggests has a morphological association with the feline members of the animal world. The snakes are named so because of the resemblance of their eyes with the eyes of a feline member of the animal kingdom, especially the eyes of cats. 

It is important to understand that cat snake is a general term that is used in day to day conversation. This term is not a part of the taxonomic classification or the binomial nomenclature system, another important point to notice is the term is used to refer to various different species of snakes, although representing different species, all species are classified under a single family. The example of cat snake families includes species like the following, Boiga cyanea (green cat snake), Boiga trigonata (Indian cat snake), Boiga nigriceps (black cat snake), Boiga forsteni (red cat snake). As represented by the binomial scientific nomenclature of the cat snake species, the majority of the species classified as the cat snakes belong to the genus called Boiga.

The article focuses on the general description of the cat snake category of snakes, the taxonomical classification of the snake, the venom and behaviour of the snake that includes the threat to the human population. The article also gives an insight into reproduction and the natural habitat of these snakes. The two most important species that are primarily discussed in the article include Boiga trigonata (Indian cat snake) and Boiga cyanea (green cat snake).

General Description of Cat Snakes

The cat snakes are a group of arboreal or semiarboreal rear-fanged snakes. The term arboreal refers to the animals that well adapted to live on trees. They are seen hanging from the tree branches. Rear fang is a term used to define the anatomical position of the venom conducting teeth. The rear-fanged animals are those that have the venom conducting tooth located posteriorly in the roof of the mouth. Generally, snakes are front fanged, cat snakes are an exception to this anatomical generalisation.

The cat snakes are classified in the family called Colubridae, the term cat snake was coined due to their similarity in the structure of eyes with cat species. These snakes have a vertical elliptical pupil, this shape of pupil is common in feline family members and are found only in cat snakes among the reptiles. The vertically elliptical pupil allows the eyes to contract into a narrow vertical slit during daytime. During nights, after sunset, the pupils of these snakes expands. The reason behind this expansion of the pupil is to allow maximum light rays to enter the eyes, which helps in creating a clear image.  This morphological adaption is important to the cat snakes because they are nocturnal animals that hunt during the night.  The most active hours for these creatures are during the twilight hours.

The venom that is found in the species of cat snakes is not fatal to the human population. The cat snake species are commonly found throughout the world, they are only not found in areas of Antarctica. The data shows that there is a total of 34 species that are classified as snake cats. Although these species are distributed globally, it is estimated they originated in Africa. African cat snakes belong as the member of the genus Dipsadoboa. This ancestor genus has recorded up to 12 species of cat snakes. An important distinction is the species of this genus is Sahara. The evolutionary history confirms that the species of the genus Boiga are native to southeast Asia, India, and Australia. It is due to the extreme adaptation abilities they are found in almost all the continents around the world.

Morphological Features

Morphology of an animal refers to the physical appearance of the animals. The most distinctive feature of these animals is the vertically elliptical eyeballs. The general morphology of these snakes is defined as animals with a laterally compressed body, that has a triangular head. The laterally compressed shape results in a very thin body structure. The head is quite distinctive from the rest of the body because of its triangular shape, due to this the head appears to be broader than the rest of the body. 

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The body size depends upon the species of the cat snakes, the general range of body size is 0.3 meters to 2.6 meters. The average size of a green cat snake is about 120cm. Sexual dimorphism can be observed in the body size of these snakes, the female members of the species are generally larger than the male members of the species. An example of such sexual dimorphism can be seen in the green cat snake species where the male body length is about 177cm and the length of the female is about 189cm. 

The general classification of cat snakes is based on the colour of the body. The colour of the body varies greatly from species to species. They are generally seen as green cat snake, black cat snake, red cat snake. Apart from the singularly coloured species, there are some species of the cat snake that have brown or black coloured spots throughout their body, an example of such a snake is Boiga multomaculata. 

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Apart from the colour of the body, another important morphological feature is the scales of the body. The scale arrangement varies slightly in every species but the common feature among all these is the presence of smooth scales that are long in shape and are obliquely arranged. The arrangement of scale is defined as the pattern in which the scales are present on the dorsal surface, side dorsal surface of the body. The ventral surface of the body does not have any scales. The scales that are present on the top dorsal surface is larger than the scale of the side dorsal body, the shape of the scale is hexagonal. The colour in between the scales is generally black. Subcaudal scales paired in a zig-zag manner. Since there is no true locomotive appendage present in the anatomy of snakes, the scales help in locomotion.

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The ventral side of the body is smooth and are coloured according to the species. The head is larger than the throat region and is triangular in shape, the tail of the snake cat is pointed to allow arboreal behaviour, that is to support the body while hanging from the trees. 

Anatomical Features

A very common feature that is found in snakes is the ability to shed their skin. The process of periodically shedding the skin is called "ecdysis”. The skin contains two skin glands that are known as a pair of anal scent glands that secrete a substance used to attract a mate, provide protection from predators, and mark territory.

The skeleton system of cat snakes are rather simplistic, this can be attributed to the fact they lack limbs that are present in other reptiles. The skeleton of the snakes consists of the vertebral column, ribs and skull. The number of the vertebrae is more as compared to humans other reptiles. Apart from the simplistic nature of the skeleton, another unique feature is the structure of the skull and teeth structure. The bones of the skull are connected by elastic ligaments, allowing a lot of stretches. An important point is bones of the lower jaw are not fused together at the front. This adaptation has evolved to allow snakes to capture large prey. 

A unique characteristic that is found in snakes including cat snakes is the nature of the teeth. The teeth of cat snakes are defined as acrodont and polyphyodont. The term acrodont refers to the anatomical positioning of the teeth, the cat snakes have teeth attached to their bone structure. Polyphyodont is defined as the ability to grow teeth multiple times during the life span. Both of these features are unique to snakes and not other members of the reptile family. Cat snake teeth are specifically defined as a rear-fanged tooth, that is the tooth are located on the posterior roof of the buccal cavity.

Another anatomical feature that is very distinguishing between cat snakes and other mammals is the presence of sense organs. While most mammals rely on the sense of sight and hearing, cat snakes rely on senses of touch and smell. Since they are heavily dependent on this sensory stimulation they have evolved unmovable eyelids, the protective covering of the eye is called brille. It is a transparent coat that covers the eyes. Another anatomical adaptation is the lack of structures as the external ear, middle ear, or tympanic membrane (eardrum). There is only the presence of a small ossicle (a type of ear bone), called the "columella," this used to detect the vibrations on the ground and helps in locomotion and predation.

Reproduction

Cat snakes irrespective of their species, that is they can belong to different species like Boiga cyanea, (green cat snake), Boiga trigonata,(Indian cat snake), Boiga nigriceps, (black cat snake), Boiga forsteni, (red cat snake), are sexually reproducing reptiles. Cat snakes are a polygamous group of snakes. The females of these species are considered oviparous reptiles, that is they lay eggs. During a single mating, a female can lay up to 10 to 12 eggs. The green cat snake species lay 10 eggs during a single mating, the mating season for these ranges from late winters to late summers. While the Indian cat snake species lays about 3 to 12 eggs per mating cycle. 

The eggs are laid in burrows and are protected by the parental generation. Upon hatching the progeny of the green cat snake is only 35 cm in length.

An interesting fact about the reproduction in cat snakes is that the female members of the species have the ability to decide whether or not to fertilize their eggs. This ability of choice is dependent on the fact that the female cat snakes can store sperm (male gamete) for up to 5 years. As mentioned earlier the reptile is a sexually reproducing animal. The male reproductive organ is the hemipenis, which is used to transfer the male gamete into the female’s body. Another unique anatomical modification is the presence of two pockets each are specialised for delayed or immediate reproduction. These pockets are essentially the site of reproduction.

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Habitat and Distribution

Cat snakes are distributed over large geographical ranges. They are native to the countries of Southeast Asia but due to strong adaptation abilities, they are found all over the world. An interesting fact to notice is that the ancestral genus of these cat snakes is found in Africa. The members of the ancestral genus Dipsadoboa are primarily found in the open woodlands south of the Sahara and tropical rainforest of the African continent.

The green cat snake or Boiga cyanea is found in southeast Asian countries. Their habitat can include areas like primary and secondary forests, including montane zones. They are also found in evergreen, semi-evergreen, moist deciduous forests. Choose dense plantation for activity and roosting. Hides in tree holes and dense vegetation. They are also found at sea levels in coastal forests. They are found in a range of countries starting from Pakistan to Australia.

The Indian cat snake Boiga trigonata is specifically found in countries like Sri Lanka, India, Pakistan, Nepal, Bangladesh, Afghanistan. They are also reported in countries like Uzbekistan, southeastern Tajikistan, and Iran.

Diet 

Similar to all the snakes’ cat snakes are carnivorous reptiles. The primary diet of a cat snake includes lizards and frogs. Depending upon the species, some big cat snakes can predate some larger animals like small snakes. They also predate rodents, mice, and frogs, toads, and tadpoles. They are occasionally seen feeding on bird species.

Taxonomical Classification

Taxonomical classification is the process of categorization of animals based on their similarity. From the discussion above it is evident that the cat snake is not a scientific term used in the classification system. Another important thing to keep in mind that the term cat snake is used to define snakes that belong to a different genus. The taxonomical classification of these animals is mentioned below.

Cat snakes are classified into kingdom Animalia, the largest level of taxonomic classification. The kingdom is further classified into phylum Chordata the essential feature is the presence of notochord. It is now a well-established fact that the cat snakes have a vertebral column (although they slack true limbs and appendages).

The phylum is further classified into the class, cat snakes belong to the class Reptilia. The class is further categorized into the order called Squamata, the essential feature of this order is the presence of scales. Cat snakes have both dorsal and side dorsal scale covering the body. The order can further be classified as a suborder called Serpentes. The unique feature of this suborder is that all the members of this suborder are limbless reptiles. 

The suborder is further classified into the Colubridae family. This family contains about 249 genres. The cat snake is commonly categorized into Boiga and Dipsadoboa genera, there are some other genera that are classified as cat snakes but are not related to the Boiga genus.  The Boiga genus contains about 34 different species classified as cat snakes, while the Dipsadoboa genus is considered as an ancestral genus that has about 11 species categorized as cat snakes. 

Example of Different Species Includes:

• Black-and-yellow mangrove snake also known as gold-ringed cat snake (B. dendrophila )

• Indian cat snake Boiga trigonata

• T. fallax

• Leptodeira annulata

The term cat snake is an umbrella term used to define species of different snakes. The name is attributed because of the resemblance of the pupil with feline members. The venom of these snakes is not fatal to humans. They are also not a threatened species. They have a global distribution. An interesting feature about their behaviour is that they are considered a nocturnal and arboreal group of reptiles. The main countries that are known for the population of cat snakes include India, Sri Lanka and Pakistan.