Small to medium, moderately stout-bodied with a short to very short tail. Largest member of the genus Causus. Adults 300 – 600 mm long, can reach 1 000 mm. Head only moderately distinct from neck. Eye round, medium in size; pupil round and edged in gold; iris dark. Colour above light- to dark-brown, with dark, diamond- or chevron-like markings, edged in white. Very prominent dark V-mark on head, pointing towards snout. Flanks with dark spots or vertical bars. Below, pearly-yellowish, dirty-white to greyish or gunmetal, uniform or with ventral shields dark-edged. Soft, velvety, somewhat-keeled dorsal scales in 17 – 21 rows at mid-body; anal entire.
Relatively short, crude fangs with no hinge action compared with adders in the genus Bitis, but maxillary rotation almost as great.
Cytotoxic. Yield: 80 – 120 mg. Bites mostly not serious, causing extreme pain, much swelling of the limb and regional swelling of the lymph nodes. However, some victims collapse from hypotensive shock and may require hospitalisation, hence bites in children or the immune-compromised should be taken very seriously. Dogs often bitten and small dogs at risk of death. No anti-venom available; treatment is symptomatic.
Moist savanna, lowland forest and fynbos where toad and frog prey abound.
Terrestrial, specialising on toads and frog prey. Largely inoffensive and docile but if aroused, hisses and puffs ferociously, inflating body to a great extent, often raising forepart off the ground, sliding forward with neck horizontally inflated. Tends to lash rather than strike. If aggressor retreats to a safe distance, snake moves off with head well-raised off the ground. Accounts for many bites, especially in KZN and the Eastern Cape. For several reasons, the name ‘Night Adder’ is misleading; often at large during the day and possessing round pupils typical of diurnal snakes (most adders have vertical eye pupils); has large scales on top of the head (most adders have small scales); reproduces by egg-laying, unlike adders which give birth to fully-developed young.