Establishing which specific snake venom is the most toxic is a somewhat complicated process that typically does not have a single clear outcome without defining certain variables first. For example, “most toxic” can refer to which snake venom is the deadliest given a certain quantity, or it could temper that initial idea by also considering how much venom is injected by a snake per bite. The toxicity of the bite can also depend on how the bite is delivered, whether the teeth only punctured the skin or if the venom managed to be injected into a vein or directly into deep muscle tissue. For many people, the deadliest snake in the world is considered to be the inland taipan of Australia, but this is certainly open to debate and interpretation.
Snake venom toxicity is typically measured in terms of median lethal dosage (LD-50) or the amount necessary to be lethal for half of a test group. This type of testing is typically performed on lab mice, and though it tends to be accurate, snake venom can potentially behave somewhat differently in a mouse compared to a human being. LD-50 measurements are commonly measured in milligrams per kilogram (mg/kg), indicating the amount of venom required to be lethal.
Using this type of measurement helps make it easier to compare toxicity levels in snakes; however, the results can still depend on how the venom is delivered. Some researchers believe that subcutaneous injections, introducing the snake venom below the skin but not necessarily into a vein, is the most accurate as it represents the majority of snake bites. In this type of experiment the most toxic snake is the inland taipan of Australia, sometimes called the “fierce snake,” with an LD-50 of only 0.025 mg/kg. This is compared to the western diamondback rattlesnake found in North America, which has venom with an LD-50 measurement of 18.5 mg/kg, making the venom of the inland taipan about 740 times more toxic than the venom of the rattlesnake.
When considering a snake bite that injects the poison directly into a vein, an intravenous injection, these numbers are different. The western diamondback rattlesnake venom has an LD-50 of 2.72 mg/kg for intravenous bites, significantly more deadly than for subcutaneous measurements. In intravenous testing, the eastern brown snake of Australia has the most toxic venom with an LD-50 of 0.01 mg/kg. These sorts of differences in measuring techniques make it difficult to establish just what snake venom is the most toxic.
Further complicating the issue is how much venom is injected with a single bite by a snake. For example, the coastal taipan of Australia has venom that is less toxic than that of the eastern brown snake of Australia. The coastal taipan, however, can inject 20-30 times more venom in a single bite, making the results of a bite from the coastal taipan potentially more fatal. Ultimately, however, these measurements are fairly academic in nature as any of these snakes can easily kill a person in a single bite and in a short period of time.