Puff Adder

Its danger comes from ecology and behaviour rather than from extreme toxicity. The puff adder is one of the most common large snakes over a huge area of Africa, including farmland and the edges of villages. It is an ambush hunter that relies on camouflage and absolute stillness, so instead of fleeing an approaching person, as many snakes do, it stays put and is trodden on or brushed against, often on a footpath at dusk. It has long fangs and injects a large dose of a venom that does serious damage, and in the rural areas where most bites occur, getting to a hospital with the right antivenom quickly is often difficult. The result is that this single species accounts for a large share of Africa's snakebite deaths and of the many more amputations and permanent injuries.

A serious bite is a medical emergency. The venom is dominated by cytotoxins, which attack cells and tissue, so within hours the bitten limb swells enormously, blisters, bruises, and begins to die around the wound. This local damage is often the worst part, sometimes destroying enough muscle and skin to require surgery or amputation, and it can lead to dangerous drops in blood pressure and problems with clotting. Deaths do occur, particularly when treatment is delayed. With prompt hospital care, antivenom, wound management, and support for blood pressure and kidneys, most patients survive, though many are left with lasting scarring or disability.

There is experimental support for it. Researchers testing whether trained dogs and meerkats could locate hidden snakes by scent found that they readily detected several species but consistently failed to detect puff adders, even at close range. The current explanation is chemical crypsis, meaning the puff adder gives off very little of the odour that predators use to find snakes, which fits perfectly with its lifestyle of lying motionless in one spot for long periods. A snake that cannot be seen and cannot be smelled is extremely hard for a mongoose, a honey badger, or a person to avoid.

Almost anywhere in sub-Saharan Africa that is not deep forest or extreme desert, including cultivated land and the outskirts of towns, because the snake follows rodents. Puff adders are most active in the warmer months and often move around and hunt in the cooler hours, so encounters peak in the early morning and around dusk. Bites frequently happen to people walking barefoot or in sandals on paths, to farm workers in fields, and to those stepping over logs or reaching into grass and woodpiles without looking. Wearing closed shoes and using a torch after dark are the simplest and most effective precautions.