Frederick McCoy formally described the inland taipan in 1879, and a second specimen turned up in 1882. Then Western science lost track of it for some 90 years, even though Aboriginal Australians had long known the animal. It resurfaced only in 1972, when a grazier found an unclassified snake head and herpetologists Jeanette Covacevich and Charles Tanner mounted an expedition that brought back 13 live specimens. This episode looks at what they found on the cracking clay plains of the Channel Country: a shy, reclusive reptile whose venom, drop for drop, is the most toxic of any snake, with one bite carrying enough to kill more than 100 adults.

Everything about the snake answers to its harsh habitat. It darkens in winter to absorb heat and pales in summer, warming itself by poking only its dark head from a fissure. It hunts rats inside those cracks and cannot afford to let bitten prey escape into the maze, so it strikes repeatedly and holds on, relying on venom fast enough to end the fight at once. The same chemistry makes a human bite a race against the clock.

• The venom combines nerve-blocking toxins, agents that force the blood to clot and then hemorrhage, muscle-destroying toxins that clog the kidneys, and an enzyme that speeds its spread.
• An older claim that Belcher’s sea snake was more venomous came from studies using different injection routes. Tested under the skin, the taipan stands alone.
• A single bite delivers 44 milligrams of venom on average, with a recorded maximum of 110.
• In 1967 a tour guide bitten in the Channel Country could not be given antivenom because of a horse serum allergy. He survived after four weeks in hospital.
• Untreated bites are estimated to kill more than 80 percent of victims, sometimes in 45 minutes, yet there are no recorded deaths since specific antivenom became available.