Which snake is the most poisonous?

Dear Matthew and Alice:

After many hours of Animal Kingdom, Wild Planet, and all those other nature programs, I still have one unanswered question concerning poisonous snakes. According to certain televised sources, the black mamba of Africa is the world's deadliest snake. Others report the Australian fierce snake, and some even say the ubiquitous sea snake is the winner. Weeks later I heard that the Australian brown snake and the African saw-toothed viper were also contenders. The confusion might stem from the fact that some sources might be ranking snakes based on the toxicity of their venom, the number of people that die from the attacks, total number of people attacked, or even the ferocity with which each snake attacks its prey. Please help me clear up this dilemma. I want to know which snake is the undisputed heavyweight champion of the most poisonous/deadliest debate.

-- Ssssssscott, the net

Many thanks for explaining why it's impossible to name the world's deadliest snake, then asking me to ignore that and name the world's deadliest snake. Snakeologists consider it a pointless debate. And anyway, you left out a few variables, most notably how much toxin is injected into the victim. Sea snakes have very toxic venom but don't deliver much in a single bite. Some snakes can even control the amount of each injection.

Luckily, none of the top candidates lives anywhere near San Diego. Unless you're one of those overhyped Survivor pinheads, or you got lost on your way home from the Olympics, it's not likely you'll need this information. Australia seems inordinately proud of the fact that every indigenous animal except the koala is lethal; and Australia is home to the fang-bearer I'll pick as top snake in the pile. But naturally, if you're in Africa with black mambas eyeing your shins, at that particular time and place the black mamba is the champ. Besides, what kind of thrilling TV documentary would it be if the narrator said, "Here we are in Africa, and oooooh, there's the dreaded black mamba, the world's 23rd most deadly snake!"

Let's use pure toxicity as our measure. That's as arbitrary as any other. Until something more humane can be devised, the standard test of toxicity is an ugly, animal-based study called the LD-50. It gives you a measure of how much venom it takes to wipe out half the critters in your lab. Results are given in milligrams of venom per kilogram of body weight. There are six basic components of snake venoms, and each species has its own particular chemical cocktail. The LD-50 champs deliver neurotoxins that have a paralytic effect on a victim. (Other components damage blood cells, blood vessels, body tissue, or prevent blood clotting.)

Top snake in the subcutaneous LD-50 test is Australia's inland taipan, a.k.a. the fierce snake (0.025 mg/kg). Second is Australia's eastern brown snake (0.036). Third through fifth are various warm-water sea snakes (0.044 to 0.079). Sixth is Australia's coastal taipan, (0.106). Your saw-scaled (not saw-toothed) viper comes in 13th (0.151), and the black mamba 23rd (0.32). Of course the inland taipan lives far from human populations, so... The mamba is fast, easily irritated, delivers a lot of venom, and lives near people, but the neighboring, less-toxic puff adder kills more people, so... If you want a more relevant sub-q LD-50, the western diamondback rattlesnake ranks 76th (18.5). The Mexican rattler is 52nd at 2.8. Until I have a train ticket to southwest Australia, they're the deadliest snakes in my world.