Dangerous Snakes: Just how deadly are they?

We all know that SA has an abundance of dangerous snakes, but just how much of a chance do we stand of becoming a victim? Johan Marais sheds some light on the local snake scene.

With all the rain of the last few weeks (March 2012) helping snakes get on the move, I’ve been inundated with photographs of freshly killed snakes that people want identified. The fear is understandable – SA is home to some of the world’s most dangerous snakes. The black mamba, for instance, is Africa’s longest venomous snake, reaching close to 4,5m. And the boomslang has, drop for drop, the most potent venom of any African snake. Yet although there are 11 deadly snake species in SA, cases of humans being bitten are rare, because these snakes are secretive and seek to escape when confronted.

The forest cobra, for example, is abundant in parts of Zululand, inhabiting thick coastal and riverine bush. It’s quick to take cover when disturbed, and I know of only two snake handlers who have been bitten in the past few years. The green mamba also prefers thick coastal bush, invariably within 15km of the sea. When threatened, it climbs higher into the trees. As for the two highly venomous backfanged snakes, the boomslang and the vine snake, they virtually never bite unless they are physically grabbed. Even if you were to walk right past one of these snakes perched on a branch, it wouldn’t attack. Victims are mostly snake handlers.

The puff adder reputedly accounts for most snake bites in SA. It is extremely common throughout the country except in true desert, dense forests and on mountain tops. It is an extremely sluggish snake that relies on its excellent camouflage – so much so that I believe most hunters and fishermen stand on a puff adder at least once in their lifetime! In fact, it is believed that many people are bitten because they accidentally stand on the puff adders. However, recent work by Prof Graham Alexander and his colleagues at Wits University shows that even puff adders seldom bite.

While doing some radio tracking on several puff adders at Kwalata Reserve north of Pretoria, they accidentally (and frequently) stood on puff adders that were hiding in the grass, yet none of those snakes made an attempt to bite. The researchers then experimented with rubber boots filled with rocks, and came to the same conclusion. So it appears the puff adder is most dangerous when on the move and accidentally stood on, but that it seldom bites. Puff adder venom is cytotoxic, or cell-destroying, causing severe pain, swelling, blistering and in many instances severe necrosis that may require a great deal of surgery. Anti-venom treatment is often required, but this depends on the severity of the bite.

The Mozambique spitting cobra also accounts for many bites. Strangely, a number of people have been bitten while asleep. It appears that the snakes enter homes under doors or through open windows. Some victims are bitten more than once. The cobra venom is similar to that of the puff adder, also causing a lot of pain, swelling and necrosis. Victims have been known to lose limbs in severe cases.

The Cape cobra accounts for a fair share of bites – reputedly causing the most fatalities in SA. It is widely distributed throughout the drier western half of the country, often inhabiting squatter camps where rodents and frogs are abundant. Because of the fast-acting neurotoxic venom, urgent hospitalisation is invariably required for bites.

The black mamba, despite its reputation for aggression, seldom accounts for bites and usually chooses to flee. If cornered or threatened, and when escape is not an easy option, it may strike more than once. Because of the massive yield of the fast-acting neurotoxic venom, such bites are extremely dangerous and often fatal. There are many stories of mambas chasing people, even horse riders, but this doesn’t really happen. Still, should you come across a black mamba, with its narrow hood spread and showing the black interior of its mouth, be extremely careful! When out in the field, don’t attempt to kill or even approach snakes. Leave them alone. When camping, keep your tent zipped up. Always carry a torch and wear shoes when sitting around the campfire, or if you go out to answer a call of nature.

Get to know the common snakes in the area you visit. Check out the first aid advice in snake books. If someone is bitten, immediately call the Tygerberg Poison Centre – 021 931-6129.

Johan Marais is the author of several books on reptiles including the best-selling A Complete Guide to Snakes of Southern Africa. He is also the owner of Reptile Ventures, a company that provides courses on snake awareness and snake handling throughout Africa. Readers are welcome to submit photographs of snakes for identification to http://reptileventures.com/