Different Types of Snakes
Snakes Come in a Variety of Types
Snakes are very specialised reptiles, the same class of animals as lizards and turtles, which have lost their limbs. There are almost 3000 different species of snake around the world, on all continents except for Antarctica.
Scientific taxonomy classifies snakes in different families, but for a layman the latin names and anatomical criteria are somewhat baffling. It is more interesting to explore the world of serpents by thinking about the different kinds of snakes depending on their strategies for catching prey, their habitat or their modes of reproduction.
Venomous and Non-Venomous Snakes
The obvious classification of snakes that most people think of immediately is into venomous and non-venomous types. As a matter of fact, most snakes are not venomous, but some species, from the families Elapidae, Colubridae and Viparedae, have developed specialised salivary glands and fangs that allow them to produce potent toxins and inject them into prey.
Venomous snakes can further be subdivided into the type of fangs that they have. Some, like the black mamba, have simple hollow fangs that are fixed in position. Others, like vipers or rattlesnakes, have hinged fangs that can rotate. Normally they are held against the roof of the mouth. To bite, the viper opens its mouth very wide, and extends the fangs, which inject venom when they stab into the victim.
Spitting cobras have come up with a particularly interesting form of self-defence, they spray venom from their fangs, without needing to bite. The venom is sprayed in a geometric pattern, hoping to hit the threatening animal in the eyes, where it can result in permanent blindness.
Different Types of Snake Venom
Venomous Snakes could also be classified by the type of venom they use. Snake venom consists mostly of proteins, and snakes can produce a mixture of up to a hundred proteins.
In general, venoms are classified into two types, neurotoxins, which affect the nervous system paralysing prey, in used mostly by snakes in the family Elapidae such as cobras, and haemotoxins, found mostly in vipers, which destroy red blood cell membranes. Generally neurotoxins act much faster than haemotoxins and are used by slower snakes which need their prey to die very quickly so they don't have to chase it.
Snake venom can also contain a variety of enzymes, such as proteases which degrade proteins, metalloproteinases, cytotoxins and cardiotoxins.
The potency of the venom is measured by LD50 values, the amount of toxin that will result in the death of 50% of the test subjects, usually mice.
The strength of the venom by itself is not the only indicator of the danger of the snake. The Australian inland taipan (Oxyuranus microlepidotus) is generally regarded as the most most venomous land snake, but being shy and reclusive, it is far less dangerous than the black mamba, which is very aggressive and fast, and will strike repeatedly.
Overall even snakes with fearsome reputations such as the cobras, mambas, or rattlesnakes, would rather not bite humans if they can possibly avoid it. Humans are too big to eat, so are really a waste of venom, and there is the possibility of damaging its fang when biting. This is why snakes have a variety of warning off humans who've stumbled on them, such as the noise made by the rattlesnake or inflating of the cobra's hood.
Catching Black Mamba Anit-Venom "Donors"
As already mentioned, the vast majority of snake species are not venomous. Of course this does not make them harmless. Many of the largest snakes do not bite and poison their prey, instead they use their enormous length and strength to suffocate the animal. In the case of snakes such the reticulated python, they "prey" can include animals as big as deer and pigs. The longest reticulated python recorded measured 22.8 ft in length.
Just because snakes are not venomous does not mean they will not bite. The boa constrictor is famous for striking repeatedly at people if it is sufficiently annoyed. Although the bites are painful, they do not inflict permanent damage.
The big, constrictor types of snakes are not the only ones lacking venom. Some serpents, such as the Barbados thread snake, are tiny, 4" in length, and rely on burrowing and eating insect larvae for survival.
A Python Eating a Huge Meal
Types of Snakes by their Habitat
You could also think about the different kinds of snakes by considering their habitats, whether land, tree or water. One theory states that snakes evolved from burrowing lizards which lost their limbs. This would mean that the original snakes were at home on the ground. However, over time some snakes, including tree boas and tree pythons evolved to climb trees, and became mostly arboreal. There is even a "flying" snake, that can glide over long distances.
Many snake species are excellent swimmers. However some spend the majority of their time in marine environments, feeding mainly on fish.
The Sea Snake
Type of Reproduction
Snakes are reptiles, so it is normal to think of them laying eggs. However some kinds of snakes, including the Boa constrictor and the green anaconda, are livebearers. Females are not really "pregnant" the way mammals are, but rather than laying their eggs, they retain them inside their bodies until they hatch and give birth to baby snakes.
The vast majority of egg-laying snakes abandon the eggs once they are laid. The king cobra, however, builds a nest and guards her eggs until they hatch. Similarly python females curl around their eggs and stay with them until the young snakes make it out.