Fig. 4.64 Causus defilippii

Distribution

Sub-Saharan Africa. See link "Distribution" at the top of the page for detailed information.

  Map 45  Causus spp.

Biology

Together with Azemiops feae, night adders are counted amongst the most primitive vipers. In appearance they resemble colubrids much more than they do typical viperids.

Relative short, triangular to oval head, covered in large shields. With a length of 2–3 mm, the fangs are very short. In contrast, the venom glands are very large, and may even extend into the first third of the body as far as the level of the heart. From a side view, the tip of the snout is pointed, protruding over the lower jaw. In C. defilippii the snout is slightly upturned. Round pupils. Short, sturdy body, slightly flattened.

C. rhombeatus may reach up to 1 m (as an exception), on average 60 cm, the other species on average smaller.

Basic colouring grey, brown, olive or other shades of green. C. resimus and C. lichtensteini sometimes bright green. There are often markings in the form of a backward-facing chevron over the head and neck; if present in C. lichtensteini and C. resimus, beginning behind the head. Dark blotches along the spine, often shaped like a rhombus or chevron, sometimes with white edges. Unmarked animals among C. rhombeatus and in particular adult C. resimus. C. bilineatus has a light-bordered stripe along its back.

Preferred prey are frogs or toads, and thus night adders are confined to mesic habitats (not rainforest areas). C. lichtensteini often found in wooded swamps. C. rhombeatus not seen in primary forests. C. resimus is best adapted to drier habitats and is therefore found in separate environments to C. defilippii in East Africa.

Nocturnal snakes, very common in certain areas, but will often come out of their hiding places during the day to sun themselves. When threatened they flatten their neck slightly and produce a loud puffing or hissing by breathing out at intervals. Slow to flee.

Risk

Night adders are a common cause of mild or moderate snake envenoming in Africa. Serious systemic envenoming has not been reported.

After the puff adder (Bitis arietans), C. rhombeatus is responsible for the majority of venomous snakebites in South Africa (Christensen 1980). In the Congo, C. maculatus is said to cause most cases of snakebite envenoming (Carme et al. 1986).

In Nigeria, night adders are considered responsible for the majority of minor bites in victims bitten while walking around at night (Warrell 1980). In a series of 10 bites by C. maculatus, one victim developed systemic signs of envenoming that quickly abated (Warrell et al. 1976c). A study of snakebites on a Liberian rubber plantation confirmed that there also most cases of snake envenoming were caused by C. maculatus (Stahel 1980).

Literature (biological)

Broadley 1983 and 2014, Broadley and Cock 1989, Doucet 1983, Hughes 1977, Mallow et al. 2003, Pitman 1974, Roman 1980, Villiers 1975

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