Jacksonville Zoo and Gardens

Puff Adder

Viperidae

Squamata

Reptilia

Sub-Saharan Africa south to the Cape of Good Hope, southwestern Saudi Arabia and Yemen

Found in all habitats except true deserts and rain forests.

A stout snake, puff adders average 3.3 ft (1 m) in length.  The head has a less than triangular shape with a blunt and rounded snout. Still, it is much wider than the neck. The rostral scale is small. The circumorbital ring consists of 10–16 scales. Across the top of the head, there are 7–11 interocular scales. 3–4 scales separate the suboculars and the supralabials. There are 12–17 supralabials and 13–17 sublabials. The first 3–4 sublabials contact the chin shields. Often, there are two fangs on each maxilla and both can be functional.  Midbody there are 29–41 rows of dorsal scales. These are strongly keeled except for the outermost rows. The ventral scale count is 123–147, the subcaudals 14–38. Females have no more than 24 subcaudals. The anal scale is single.  The color pattern varies geographically. The 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. Iris color ranges from gold to silver-gray. 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 may be 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.

Up to 15 years (in captivity)

About 2 years

In the wild, they eat a variety of mammals, birds, amphibians and lizards; in the Zoo, they are fed rodents.

Not listed

Normally a sluggish snake relying on camouflage for protection, puff adders move primarily rectilinear.  They use their broad ventral scales in a caterpillar fashion aided by their 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 15 ft (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 forward. These snakes rarely grip their victims, instead releasing quickly to return to striking position.

Mostly nocturnal, they rarely forage actively, preferring instead to ambush prey as it happens by.

Females produce a pheromone to attract males, which engage in neck-wrestling combat dances. They give birth to large numbers of offspring: litters of over 80 have been reported, while 50–60 is not unusual. Newborns are 4.9 – 6.9 in (12.5–17.5 cm) in length.  Very large specimens, particularly those from East Africa, give birth to the highest numbers of offspring.

Their long fangs permit deep penetration and envenomation of prey. The hinged-fang mechanism allows for fang storage against the roof of the mouth when not in use. The structure of the hinge mechanism is unique; the lateral process of the palatine bone is absent, each maxilla is cuboidal and bears a single enlarged maxillary tooth (several replacement fangs lie behind the functional fang), the maxillary fang has a duct on its anterior face, and the elongate ectopterygoid serves as a lever to erect or depress the fang.

The venom has cytotoxic effects and 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 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 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 occur and can result in loss of digits and limbs.

Despite all of this, deaths are exceptional and probably occur 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.

Pit-organs lie on each side of the head between the nostril and eye and contain infrared receptors. They allow the snake to detect prey whose body temperature differs from background temperatures.

Its wide distribution, common occurrence, large size, potent venom, and willingness to bite make it responsible for more fatalities than any other African snake.  Although puff adders are far from the deadliest venomous snake in Africa, they cause more venomous bites to humans on an annual basis then any other.  One reason for this is their tendency to use human footpaths after dark.  Since footwear is minimal or non-existent for many in Africa, nocturnal encounters result in a lot of puff adder bites.

A female puff adder from Kenya in a Czechoslovakian zoo once gave birth to 156 young, the largest litter for any species of snake in the world.

Puff adders (Bitis arietans), like many other snakes, hiss as part of their defensive repertoire. The hisses have a clear quadraphasic pattern consisting of an initial exhalatory hiss, a brief transitional pause, an inhalatory hiss and a rest or breath-holding phase. Simultaneous recordings of body diameter, electrical activity in the intrinsic laryngeal musculature, airflow through the nasal passageway and sound production revealed that the anterior respiratory tract plays a passive role in hissing and that the costal pump is responsible for generating the quadraphasic pattern. During hissing, B. arietans uses the same mechanics for normal respiratory ventilation in snakes. Analyses of artificial hisses reveal that the anterior respiratory tract of B. arietans has little ability to modify an exhalant airstream acoustically. The combination of the simple ventilatory mechanics used during hissing and the lack of acoustic modification of the exhalant airstream results in the production of an acoustically simple hiss. Cross-correlation matrix analyses of a variety of snake hisses showed a high degree of acoustic similarity between the sounds, almost approaching the levels determined for white noise. This high level of acoustic similarity reflects the low level of acoustic specialization within the sounds produced by snakes and the low potential for encoded information content.

There are two subspecies: Bitis arietans arietans (MERREM 1820) & Bitis arietans somalica (PARKER 1949).  The former is the dominate, more widespread subspecies while the latter, also known as the Somalia puff adder, is found only in Somalia, eastern Ethiopia, and northern Kenya.

Snake-charming has long been associated with Morocco and North Africa. The snake species most frequently featured are Egyptian cobras (Naja haje), vipers (Vipera lebetina) and the puff-adder (Bitis arietans). Snake charmers usually appear at the main open-air markets, or souks, and rapidly gather a large crowd. Contrary to popular belief, this is not usually an activity aimed primarily at tourists, except in coastal resorts or in major tourist destinations. Modern-day snake charmers usually employ a battery-operated public address system through which they exhort their audience to purchase small pamphlets containing magic formulae for protection from snake-bite or other magical charms. The audience is regularly challenged to step forward and approach the snakes; “25 Dirhams if anyone dares to touch these dangerous snakes!” Despite 25 Dirhams (approximately $3) being equivalent to a day’s wages for many, this offer is never taken up. More snakes are produced from a series of boxes or sacks, are roughly handled by the charmer and his family, and once again the effectiveness of the spells in the booklet being sold is loudly advertised. An assistant moves within the crowd gathering handfuls of money in exchange for the book.

Close examination of the snakes reveal the charmer’s secret. The mouths of the snakes are carefully stitched closed with fine twine. Just enough of a gap is left to allow the snake’s tongue to flicker though. As it is an almost universal belief that the venomous bite is delivered by the forked tongue, this deception is entirely effective. Snakes thus treated frequently develop fatal mouth infections, and are, of course, unable to feed. They survive long-enough to provide a good spectacle, however, and when obviously ill are disposed of and replaced by freshly caught specimens.

In tourist destinations, such as the famed Jemaa el Fna square in Marrakech, literally dozens of snake charmers ply their trade. The unwary tourist who takes a photograph of these activities is likely to find themselves on the receiving end of very aggressive demands for $20 or more for each picture unless a more agreeable rate is negotiated in advance!

Puff adders were part of the Jacksonville Zoo collection off-and-on from 1966 to 1980, and have once again been part of our collection since 1997.  One of our specimens has been here since 1997 and is of the common nominate subspecies, Bitis arietans arietans.

6/09