specimens never settle down in captivity, always hissing and puffing when approached. Venom 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. The venom has cytotoxic effects and is one of the most toxic of any vipers based on LD50. The 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