Most venomous land snake

The most toxic terrestrial snake in the world is the inland taipan, aka small-scaled snake (Oxyuranus microlepidotus) of Queensland and western New South Wales in Australia. This up-to-1.7-m-long (5-ft 7-in) snake is a specialist for the baking heat of the channel country black soil floodplains where it hunts for mammals in the cracked soil. Like the related coastal taipan (O. scutellatus), it preys on dangerous types of native mammals that would be able to injure or even kill a snake. Thus, these snakes evolved under selection pressure to produce extremely potent venom (and large quantities of it) in order to overwhelm their quarry before it can retaliate. The estimated human lethal dose of inland taipan venom is a mere 1 mg (0.00004 oz), and these snakes are capable of delivering over 100 mg (0.004 oz) of venom in one bite. The coastal taipan is less toxic, with the lethal dose estimated at 2 mg (0.00008 oz), but is capable of delivering over 500 mg (0.018 oz) of venom. Therefore, while the inland taipan is more toxic, the coastal taipan delivers proportionally more lethal doses per bite.

It has an LD50 of around 0.01–03 mg/kg; this figure represents the dose required to prove fatal to 50% of a test population. The average venom yield after milking is 44 mg (0.00155 oz) but one male specimen yielded 110 mg (0.00385 oz), enough to kill 250,000 mice or 125 men.

Despite being the world’s most toxic snake, there are no confirmed deaths on record for the inland taipan due to the remoteness of its native range. Most bites have occurred from snakes in captivity, with the victims able to rapidly receive medical treatment.

In contrast, there are an abundance of deaths on record for the coastal taipan, particularly from the population that lives in Papua New Guinea. However, the number of deaths from the coastal taipan are far less than occur from other snakes across the world, particularly in comparison to what are known as the "big four" in India: blue krait (Bungarus caeruleus), Russell's viper (Daboia russelii), saw-scaled viper (Echis carinatus) and spectacled cobra (Naja naja). Collectively, these four species are believed to be responsible for up to 1 million snakebites in the subcontinent, resulting in 50,000–100,000 deaths, and up to half a million cases of severe permanent injury.

With an LD50 of 0.044 mg/kg, the most venomous marine snake is the Dubois' seasnake (Aipysurus duboisii), found around Papua New Guinea, New Caledonia and the northern, eastern and western coastal areas of Australia. However, the beaked seasnake (Hydrophis schistosus) is responsible for the most deaths from seasnake envenomation due to it being a specialist for in-shore estuary habitats, and therefore being commonly entangled in fishermen’s nets.