An Introduction to the Viperinae and a closer look at the Gaboon Vipers
Vipers are probably among the most misunderstood animals on this planet. Few other creatures have so many myths and tales ranked around them and are the subject to so many prejudices and misconceptions.
Their shape and often astounding colors have fascinated humans for millennia and they continue to be some of the most mythical and fascinating animals on earth. They are often portrayed as vicious, mean and killer creatures when in fact, they are the exact opposite; living remote and hidden lives with no intent get in any sort of confrontation.
On this page, I will introduce this fascinating genus of snakes to you, including the classification, venom apparatus, venom composition and a special view on my favourite species of vipers, the gaboon vipers, Bitis gabonica/rhinoceros.
Classification and basic Information
Vipers are separated into 4 main subfamilies, the Viperinae, Crotalinae, Causinae, and Azemiopinae. This page will focus only on the subfamily Viperinae. The other subfamilies will be introduced separately.
The Viperinae include 66 species distributed across 12 Genera. Generally, they are short and stout bodies snakes with a characteristic triangular head shape and about 50cm – 120cm in length. Some species however, like the Gaboon Viper (Bitis rhinoceros) can reach and impressive length of 2 m. These massive snakes are the largest of all Vipers, they have the longest snake fangs in the world (up to 5 cm when fully grown) and can deliver the largest quantity of venom (500mg) of any snake in the world.
Old World Vipers are mostly ambush predators, which means that they can sit in the same spot for many days and wait their prey to pass by.
Snakes mostly rely on their sense of smell to detect their prey. By regularly tasting the air with their tongue, they will recognize prey approaching, even at night.
Once close enough, they will strike at an incredible speed and usually hold their prey in their jaws until it succumbs. Some smaller vipers like most European Vipers (Genus Vipera) will let go of their prey after striking to avoid risking injury. All Vipers can strike at an incredible speed and will can bite, inject venom and release their prey in less than a second.
Old World Vipers are seldom seen actively hunting or searching for prey. If a Viper is seen on the move, it may be changing its spot, basking for some energy in the sun, or on the lookout for a mate during mating season.
Generally, a viper will flee if it notices a threat, such as humans approaching. However, if confronted it will hiss very loudly, puff its body up to look bigger and strike if the treat does not back off. Some Vipers have such good camouflage that they will trust it to conceal them completely and not move at all. Most accidents happen because people step on the snake they did not even see and get bit, which is neither the snakes, nor the humans fault.
The Viperidae possess the most advanced fang and venom delivery system of all snake species, so-called solenoglyphous fangs. As seen in the image, a Viper can fold their massive fangs back into their mouth. When they strike, they will open their mouth up to 160° wide and unfold their fangs. Like a needle, the fangs are hollow and directly connected to the venom gland to inject their prey with venom. This entire process goes down in less than a second. Sometimes, the animal may even realize that it has been injected with venom until it dies.
Vipers regularly shed and replace their teeth to in case one is damaged. The teeth are protected by thin lavers of skin which are pulled back when the viper ovens its mouth and unfolds its fangs to inject their prey with deadly venom.
Roughly 90% of the venoms dry weight is protein, composed of a large variety of enzymes, polypeptide toxins and proteases. The enzymes include hydrolases (proteinases, endo- and exo- peptidases, phosphlipases) hyaluronidase and activators of inhibitors of the preys physiological mechanisms. Almost all venomos contain L – amino acid oxidases, phosophomono- and diesterases, phospolipase A2 and peptidases. Phospholipase A2 are the most wide spread of all snake venom enzymes, attacking mitochondria, red blood cells and leukocytes, peripheral nerve endings and skeletal muscles, causing haemorrhage, necrosis and flacid paralysis in their prey.
All Viperid venoms act mostly hemotoxic and haemorrhagic, attacking both the prey clotting mechanism, causing tissue damage and persistent bleeding, or the victims blood pressure, causing the victim to die of shock, stroke or complete cardiac arrest. Although Viperid venoms are relatively weak compared to some elapids, the composition of their venom makes a bite highly uncomfortable and extremely painful.
Snake Venom Metalloproteases (SVMP) are a special type of protein consisting of Metalloprotease, disintegrin-like, and cysteine rich domains that are common in vipers and responsible for potent haemorrhages. They are associated with a wide range of functions but the plesiotypic effect seems to be the induction of haemorrhages. This is the result of proteolytic cleavage of basement membrane components present in capillary vessels, which likely result in the distention of the capillary wall, the disruption of the endothelial cell integrity, and, ultimately, extravasation.
These enzymes have evolved from a type of serine proteases and are almost exclusively found in the venoms of viperid snakes. This toxin form contributes to the profound, rapidly developing swellings common after viperid envenomation. They due this mostly by binding to specific amino acid sites in substrates like lysine or arginine, which may alter the function of thrombin, a vital factor when it comes to blood clot formation. Additionally, venom kallikrein enzymes cleave to fibrinogen which is necessary to form a stable clot. By reducing the available fibrinogen for clot formation, haemorrhages are incudes and the victim starts to bleed into vital internal tissues.
Now, I want to introduce you to my personal favourite Viperinae species – the Gaboon Viper
The Gaboon Viper
These huge and beautiful vipers live in the vast forests of both western and eastern Africa. They are viviparous and give birth to roughly 10 – 45 live you snakes. During mating season, males will get really active and engage in combat sparring to increase their chances of mating. Because of their massive size, these snakes can take down prey up to the size of a small antelope, but usually they feed off other small mammals.
Previously, the gaboon vipers were separated into two subspecies. Recently however, the subspecies Bitis gabonica rhinoceros has been assigned full species status, separating the gaboon vipers into Bitis gabonica (eastern gaboon viper) and Bitis rhinoceros (western gaboon viper). The two species are nearly identical, separated by only a few physical features.
First of all, the western gaboon vipers, Bitis rhinoceros, grows a few centimeters larger, and with 200cm adults it is the larges known true viper species in the world. Both species are absolutely massive in body size and have a fat, sluggish body and a huge triangular head.
Bitis gabonica lacks the rhino-like horns typical for the western species. Both species have a series of triangular body markings which make them perfectly camouflaged in leaf litter and on the forest floor. The exact pattern is almost impossible to describe in words, but it is stunningly perfect camouflage and beautiful in shape.
The gaboon vipers are typical ambush predators. The often hide for days in the leaf litter, where they are perfectly camouflaged, and wait for prey to pass. They, they strike with such and incredible force and accuracy that the victims has zero chance of escaping.
Because of their size, these massive vipers usually just hold on to their prey and wait until the fast acting and potent hemotoxins and cytotoxins complete their work. These vipers can strike and envenomate the victim in less than half a second and deliver probably the largest quantity of venom of any snake in the world – up to 500mg per bite.
Their fangs are also the largest fangs ever recorded of any venomous snake and can get up to 5.5 cm long. Because of their docile and secretive nature, bites are extremely rare and no fatalities have ever been recorded. Their is also good polyvalent antivenom cover for both species. However, a bite from this species must be treated as a medical emergency and can have fatal consequences.
In my opinion, these are some of the most interesting and fascinating snakes on this planet.
I hope you enjoyed this article and that you learned something about the old-world vipers. For further reading, check out my “venomous snakes” section or read some of my “book reviews”.
If you are interested in my sources, click HERE!