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Eastern Gaboon Adder

VERY DANGEROUS

Very large and fat. Adults 1 200 – 1 400 mm; up to 1 800 mm in East Africa. Tail very short, especially in females. Head very broad, triangular, and distinct from neck; covered with small keeled scales. Eyes round; pupil vertically elliptical; iris pale-creamy, bluish, or pinkish to orange. Colour above a mix of purple, pink, browns and white or cream. 10 – 12 rectangular white markings on back. Flanks appear decorated with butterfly wings alternating with purple half-moon patterns. Head creamy-white above with two black triangles on the side – one below eye, one extending to angle of the jaw. Ventrally, uniformly dirty-cream with dark blotches. Heavily-keeled dorsal scales in 35 – 46 rows at mid-body, except for outermost rows which are smooth; anal entire.

Hinged front fangs; 20 – 30 mm in adults; 50 mm recorded in a 1 800 mm specimen from Kenya.

Potently cytotoxic, causing severe local pain, extensive swelling and blistering, compartmental syndrome, necrosis and hypovolaemic shock. Pro-coagulant haemotoxic component produces bleeding. Although lethal dose (LD50) in mice is less than that of Puff Adder venom, Gaboon Adder venom yield is much higher: 500 – 900 mg, averaging 600 mg. Combination of large fangs and large volumes of venom make for extremely serious bites. Cardio-toxin causes cardiac arrhythmia. Few recorded bites; those in snake handlers ranging from mild to very serious. Collapse within 15 minutes after a bite in a snake-keeper bitten on hand during feeding response when water dish removed from cage. Large quantities of polyvalent anti-venom administered intravenously saved victim’s life. Bite-site responded well to good wound-care, leaving some scarring. A bite from this snake is a medical emergency. Polyvalent anti-venom is available.

A species typical of East-African Coastal Mosaic which extends to area of lowland forest at the foot of the eastern escarpment in Zimbabwe, marginally penetrating into Afromontane region at top of escarpment, via forested river-valleys. Elsewhere associated with evergreen forests and tropical savannas in high rainfall areas. In South Africa, associated coastal forest-margins within moist, tropical-grassland matrix, and secondary dune forests along coast.

Nocturnal, ambush predator of mild disposition; rarely bites even when antagonised. Preys on small mammals, favouring prey of less than 18 % of their own body-mass. In SA, preys on rodents of 100 – 200 g (Vlei Rats, Red Veld Rats) and ground-living birds (Thrushes, Robin-chats). Occasionally, extremely large prey taken: a 2 075 g female snake found run-over near St Lucia (KZN, SA) had consumed an adult Large-spotted Genet of 2 139 g. Recent photographs by a game ranger in KZN showed another specimen consuming an adult Large-spotted Genet. Preying on a few, large prey rather than numerous, small ones, enables snakes to conserve energy by reducing need to locate new prey patches; perhaps also reducing demand to produce energy-consuming venom.

Mainly nocturnal and highly sedentary, remaining static for 74.5 % – 95.1 % of the time for up to 90 days. Emerges from cover to bask, search for new prey patches or, in males, search for mates. During the autumnal breeding season males cover large distances (up to 1 000 m during 24 hours) in search of females. While crossing roads that traverse their habitat, many killed by vehicles.
Reproduces by giving birth to fully-developed young. Mating in autumn, birth in late summer.