Puff Adder

(Bitis arietans)
VERY DANGEROUS!

Adults are thick and heavy bodied snakes which rarely exceed 1 m in maximum head-body length in this region. In East Africa specimens as large as 1,7 m have been recorded. The head is large, flattened, triangular in shape, has large nostrils pointing vertically upwards and is covered with small, keeled, overlapping scales. The basic dorsal colour is variable from blackish to brown, light brown, orangey, yellowish to straw yellow, with a certain regional consistency. The back has a row of backward pointing, dark brown to black, pale-edged chevrons and transverse bars on the tail. Specimens from the moister eastern areas tend to be darker, while specimens from the more arid western areas tend to be paler. Puff adders tend to become active at dusk, although they may bask and also move about during the day. When hungry it will take up an ambush position to waylay its small mammal prey, consisting mainly of ground-living mice and rats, although birds, lizards and toads may also be taken. This snake is ovoviviparous, which means that it reproduces by retaining the eggs with the developing fetus until full term.

The puff adder is probably the most widespread snake in Africa, avoiding the severe parts of the Sahara desert, tropical rain forests and high altitudes, it extends from the southern Cape to southern Morocco and also into southern Arabia. In southern Africa it may be found in most areas, but it avoids the extreme desert conditions, dense forests and altitudes above 2000 meters.
The venom is cytotoxic with strong haematoxic and some cardiotoxic effects and large volumes are produced. It causes severe pain, swellings in the bitten limb, hemorrhages and nausea. Death is caused by secondary effects, s. a. kidney failure, due to severe swellings. The long fangs (12 - 18 mm) assure that the venom is injected rather deeply. Even if the patient does not die, serious necrosis usually follows the swellings. In most cases of puff adder bites the use of antivenom is essential.

Mating may take place from late autumn to early spring, according to the area. Males are known to engage in combat to compete for a female. The young are born from late summer into early autumn. New born young tend to be from 15 to 20 cm in length and average batch sizes in our area vary from 20 to 40.

Normally a sluggish species that relies on camouflage for protection. Locomotion is primarily rectilinear, using their broad ventral scales in a caterpillar fashion and aided by their own weight for traction. When agitated, they can resort to a typical serpentine movement and move with surprising speed.

Although mainly terrestrial, these snakes are good swimmers and can also climb with ease; often they are found basking in low bushes. One specimen was found 4.6 m above the ground in a densely branched tree.

If disturbed, they will hiss loudly and continuously, adopting a tightly coiled defensive posture with the fore part of their body held in a taut 'S' shape. At the same time, they may attempt to back away from the threat towards cover. They may strike suddenly and with very high speed, doing so to the side as easily as forwards before returning quickly to the defensive position, ready to strike again. During a strike, the force of the impact is so strong and the long fangs penetrate so deeply, that prey items are often killed by the physical trauma alone. They are apparently able to penetrate soft leather.

They can strike to a distance of about one-third of their body length. Juveniles, however, will launch their entire bodies forwards in the process. These snakes rarely grip their victims, instead releasing quickly to return to striking position.

Behaviour

Venom

This species is responsible for more fatalities than any other other African snake. This is due to a combination of factors, including its wide distribution, common occurrence, large size, potent venom that is produced in large amounts, long fangs that inject it deeply, their reliance on camouflage which makes these snakes reluctant to flee, their habit of basking by footpaths and sitting quietly when approached, and their willingness to bite.

The venom is one of the most toxic of any viper. The LD50 values in mice vary: 0.4-2.0 mg/kg IV, 0.9-3.7 mg/kg IP, 4.4-7.7 mg/kg SC. Mallow et al. (2003) give an LD50 range of 1.0-7.75 mg/kg SC. Venom yield is typically between 100-350 mg, with a maximum of 750 mg. Brown (1973) mentions a venom yield of 180-750 mg. About 100 mg is thought to be enough to kill a healthy adult human male, with death occurring after 25 hours or more. The average specimen may have enough venom to kill 4 to 5 men.

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 there is severe pain and tenderness, but in the latter there is widespread superficial or deep necrosis. 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 oedema, which may become extensive, shock, watery blood oozing from the puncture wounds, nausea and vomiting, subcutaneous bruising, blood blisters that may form rapidly, and a 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 occurs and can result in loss of digits and limbs.

Despite all of this, deaths are exceptional and probably occurs in less than 10% of all untreated cases, usually in 2-4 days from complications following blood volume deficit and a disseminated intravascular coagulopathy. Most fatalities are associated with bad clinical management and neglect.

Lifestyle

Found in all habitats except true deserts and rain forests. Most often associated with rocky grasslands.

Breeding

Females produce a pheromone to attract males, which engage in neck-wrestling combat dances. A female in Malindi was followed by seven males. They give birth to large numbers of offspring: litters of over 80 have been reported, while 50-60 is not unusual. Newborns are 12.5-17.5 cm in length. Very large specimens, particularly those from East Africa, give birth to the highest numbers of offspring. A Kenyan female in a Czech zoo gave birth to 156 young: the largest litter for any species of snake in the world

Did you know?

Does well in captivity, but there are reports of gluttony. Kauffeld (1969) mentions that specimens can be maintained for years on only one mouse a week, but that when offered all they can eat, the result is often death, or at best wholesale regurgitation. They are bad-tempered snakes and some specimens never settle down in captivity, always hissing and puffing when approached