The puff adder (Bitis arietans ) is a venomous viper species found in savannah and grasslands from Morocco and western Arabia throughout Africa except for the Sahara and rainforest regions. It is responsible for causing the most snakebite fatalities in Africa owing to various factors, such as its wide distribution, frequent occurrence in highly populated regions, and aggressive disposition. Two subspecies are currently recognized, including the nominate subspecies described here.
The Puff adder is a venomous viper species found in Sub-Saharan Africa and on the Arabian peninsula. This snake is responsible for causing the most snakebite fatalities in Africa owing to various factors, such as its wide distribution, frequent occurrence in highly populated regions, and aggressive disposition. The color pattern of Puff adders varies geographically. Their head has two well-marked dark bands: one on the crown and the other between the eyes. On the sides of the head, there are two oblique dark bands or bars that run from the eye to the supralabials. Below, the head is yellowish-white with scattered dark blotches. Dorsally, the ground-color varies from straw yellow, to light brown, to orange or reddish-brown. This is overlaid with a pattern of 18-22 backwardly-directed, dark brown to black bands that extend down the back and tail. Usually, these bands are roughly chevron-shaped but maybe more U-shaped in some areas. They also form 2-6 light and dark cross-bands on the tail. Some populations are heavily flecked with brown and black, often obscuring other coloration, giving the animal a dusty-brown or blackish appearance. The belly is yellow or white, with a few scattered dark spots. Newborn young have golden head markings with pinkish to reddish ventral plates toward the lateral edges.
Puff adders are found in most of sub-Saharan Africa south to the Cape of Good Hope, including southern Morocco, Mauritania, Senegal, Mali, southern Algeria, Guinea, Sierra Leone, Côte d'Ivoire, Ghana, Togo, Benin, Niger, Nigeria, Chad, Sudan, Cameroon, Central African Republic, northern, eastern and southern Democratic Republic of the Congo, Uganda, Kenya, Somalia, Rwanda, Burundi, Tanzania, Angola, Zambia, Malawi, Mozambique, Zimbabwe, Botswana, Namibia and South Africa. These snakes also occur on the Arabian peninsula, where they are found in southwestern Saudi Arabia and Yemen. They have also been reported to be found in the Dhofar region of southern Oman. Puff adders live in all habitats except true deserts, rain forests, and (tropical) alpine habitats. They are most often associated with savannahs and rocky grasslands.
Puff adders are solitary and nocturnal creatures. Although they spend most of their time on the ground, these snakes are good swimmers and can also climb with ease; often they are found basking in low bushes. One specimen even was found 4.6 m above the ground in a densely branched tree. Puff adders are normally sluggish and rely on camouflage for protection. When agitated, they can resort to a typical serpentine movement and move with surprising speed. If disturbed, these snakes will hiss loudly and continuously, adopting a tightly coiled defensive posture with the forepart of their body held in a taut "S" shape. At the same time, they may attempt to back away from the threat towards cover. Puff adders may strike suddenly and fast, to the side as easily as forwards, before returning quickly to the defensive position, ready to strike again. They can strike to a distance of about one-third of their body length, but juveniles will launch their entire bodies forwards in the process. These snakes rarely grip their victims, instead releasing quickly to return to the striking position.
This species is responsible for more snakebite fatalities than any other African snake, due to a combination of factors, including its wide distribution, common occurrence, large size, potent venom that is produced in large amounts, long fangs, and their habit of basking by footpaths and sitting quietly when approached.Show More
The venom has cytotoxic effects and is one of the most toxic of any vipers based on LD50. The LD50 values in mice vary: 0.4–2.0 mg/kg intravenously, 0.9–3.7 mg/kg peritoneally, and 4.4–7.7 mg/kg subcutaneously (SC). Mallow et al. (2003) give an LD50 range of 1.0–7.75 mg/kg SC. Venom yield is typically 150–350 mg, with a maximum of 750 mg. Brown (1973) mentions a venom yield of 180–750 mg. About 100 mg are thought to be enough to kill a healthy adult human male, with death occurring after 25 hours.
In humans, bites from this species can produce severe local and systemic symptoms. Based on the degree and type of local effect, bites can be divided into two symptomatic categories - those with little or no surface extravasation, and those with hemorrhages evident as ecchymosis, bleeding, and swelling. In both cases, severe pain and tenderness occur, but in the latter, widespread superficial or deep necrosis and compartment syndrome are seen. Serious bites cause limbs to become immovably flexed as a result of significant hemorrhage or coagulation in the affected muscles. Residual induration, however, is rare and usually these areas completely resolve.
Other bite symptoms that may occur in humans include edema, which may become extensive, shock, watery blood oozing from the puncture wounds, nausea and vomiting, subcutaneous bruising, blood blisters that may form rapidly, and painful swelling of the regional lymph nodes. Swelling usually decreases after a few days, except for the area immediately around the bite site. Hypotension, together with weakness, dizziness, and periods of semi- or unconsciousness is also reported.
If not treated carefully, necrosis will spread, causing skin, subcutaneous tissue, and muscle to separate from healthy tissue and eventually slough with serous exudate. The slough may be superficial or deep, sometimes down to the bone. Gangrene and secondary infections commonly occur and can result in loss of digits and limbs.
The fatality rate highly depends on the severity of the bites and some other factors. Deaths can be exceptional and probably occur in less than 15% of all untreated cases (usually in 2–4 days from complications following blood volume deficit and disseminated intravascular coagulation), although some reports show that severe envenomations have a 52% mortality rate.Most fatalities are associated with poor clinical management and neglect.Show Less
Puff adders are carnivores. Their prey includes mammals, birds, amphibians, tortoises and lizards. Juveniles feed on small rodents, insects, and small frogs.
Puff adders are polygynandrous (promiscuous) meaning that both males and females have multiple partners. Their mating season usually takes place between October and December. During this time females produce a pheromone to attract males, which engage in neck-wrestling combat dances. Puff adders are viviparous and females give birth to 50-60 live young after the gestation period that lasts 136-159 days. Newborns are 12.5-17.5 cm in length; they are completely independent at birth and are ready to care for themselves. Young Puff adders usually become reproductively mature when they are 4 years old.
There are no major threats to Puff adders at present.
Puff adders play are important predators in their ecosystem as they control populations of many prey species they feed on. They also help control populations of pests as these snakes are often found near human settlements and prey on rodents. Young Puff adders prey on various insects and also can play a useful role for farmers.