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Mildly Venomous Snakes Facts vs Fiction


Many snakes possess some type of venom gland and enlarged teeth to incapacitate prey. The toxicity of the venom varies greatly, with some snakes such as Black Mambas and Cape Cobras have extremely toxic venom which is of great medical significance to humans. I will not be discussing these dangerous snakes farther I will be putting the misconceptions about mildly venomous snakes to rest. You will have noticed that in many field guides some snakes are marked mildly venomous but whose venom has no effect on humans it is my opinion that in these guides these species should be marked as harmless with a notation that they do possess venom which is of no medical significance to humans. Also people who do not know very much about snakes may freak out at any mention of the word venomous even if the snake is marked as mildly venomous.

Mildly Venomous Back Fanged Snakes

Many colubrid species have a modified salivary gland called a Durvernoy’s gland and enlarged rear teeth. This does not make them dangerous and I will give a quick example of the North American Garter Snakes. North American Garter Snakes possess a Duvernoy’s gland and slightly enlarged back teeth, now everyone panics and thinks they will get a reaction if bitten. I have taken a bite from a garter snake with no effects. I believe from their behavior with eating live prey that they are grab and eat predators that do not use any venom to subdue prey. I have observed them regurgitating live earthworms, if they can’t kill earth worms with their ” venom” they can’t have an effect on people. It is my theory that many back fanged snakes which eat prey that cannot harm them and are easy to over power such as frogs, toads, lizards and fish are so called ” grab and eat” predators which use their venom very little and if they do use venom it is extremely mild and of no medical significance to humans. Even if swelling or discoloration of skin occurs from some of these snakes I do not think we should panic as this occurs from some insect bites and no one goes crazy about that. That said there are some back fanged snakes which can cause medical problems with only three species having caused death in humans see below for list.

List of Medically Significant Back Fanged Species 

Boomslang ( deadly)
African Vine Snake ( deadly)

Asian Keelback Snake ( deadly)

Mangrove Snake 

Asian Vine Snake

False Water Cobra

Montpellier Snake

Large Boiga species such as Blanding’s Tree Snakes

Olive Sand Snake

Mildly Venomous Elapids
Some people consider some medically significant elapid species as mildly venomous. Two examples would be the Cape Coral Snake and the Shield Nose Snake. Both have caused deaths in children and although not considered lethal to a healthy adult they can still cause serious medical problems and, if bitten you should seek medical help. Another species considered not lethal but which can have a nasty bite is the South African Garter Snakes not to be confused with the North American Garter Snakes to whom they are not related. These smaller elapids should not be considered mildly venomous and a bite should be taken seriously. Some mildly venomous elapids include the Harlequin snakes whose bite can cause pain and pain killers may be required.

Mildly Venomous Viperids

Some smaller adder species such as the Namaque Dwarf Adder can be considered as mildly venomous as they are so small that a bite will cause some pain and swelling but no real medical worries, patients should still go to a hospital for treatment just in case. Night Adders which are sometimes considered mildly venomous can cause serious bites  but not life threatning. White Lipped Tree Vipers and Copperheads are not mildly venomous! No matter what the seller tells you bites from these species sometimes require anti venom which is not available in South Africa and have caused deaths in adults. 2 to 3 people die each year from Copperhead bites in the USA where they are native and anti venom is readily available. The starting dose of anti venom for a Copperhead bite is 8 vials, this anti venom cost about $1500 dollars a vial so do the math and you will rethink the potential health effects and treatment costs of your ” mildly venomous” snake.
When Should you Worry about a Bite?

If bitten by any of the elapids or vipers I have mentioned, I would advise that you seek medical treatment. With regards to the mildly venomous colubrids most will never require medical care, other than those on my list and even then I would only go to the ER should severe swelling, extreme pain or tissue necrosis develop. You are unlikely to experience symptoms other than these.